     Notice: This opinion is subject to correction before publication in the PACIFIC REPORTER.
     Readers are requested to bring errors to the attention of the Clerk of the Appellate Courts,
     303 K Street, Anchorage, Alaska 99501, phone (907) 264-0608, fax (907) 264-0878, email
     corrections@akcourts.us.



              THE SUPREME COURT OF THE STATE OF ALASKA

JOSEPH D. HUIT,                                   )
                                                  )    Supreme Court No. S-15514
                     Petitioner,                  )
                                                  )    Alaska Workers’ Compensation
     v.                                           )    Appeals Commission No. 13-016
                                                  )
ASHWATER BURNS, INC., et al.,                     )    OPINION
                                                  )
                     Respondents.                 )    No. 7111 – June 17, 2016
                                                  )

             Appeal from the Alaska Workers’ Compensation Appeals
             Commission.

             Appearances: Robert A. Rehbock and Andrew D. Wilson,
             Rehbock & Rehbock, Anchorage, for Petitioner. Robert L.
             Griffin and Aaron M. Sandone, Griffin & Smith, Anchorage,
             for Respondents. Laura Fox, Assistant Attorney General,
             Anchorage, and Craig W. Richards, Attorney General,
             Juneau, for Amicus Curiae State of Alaska.

             Before: Stowers, Chief Justice, Fabe, Winfree, and Bolger,
             Justices. [Maassen, Justice, not participating.]

             WINFREE, Justice.
I.    INTRODUCTION

             This appeal presents our first opportunity to consider whether City &
Borough of Juneau v. Thibodeau,1 holding that a superior court decision remanding a
case to an administrative agency is not a final judgment for purposes of appeal to this
court,2 should apply to Alaska Workers’ Compensation Appeals Commission decisions.
We conclude that it should.
             This appeal also presents our first opportunity to consider, at least in part,
the legislature’s 2005 amendments to the Alaska Workers’ Compensation Act’s
presumption analysis. We reverse the Commission’s application of that analysis in this
case and modify its earlier precedent.
II.   OVERVIEW OF THE RELEVANT LEGAL ISSUES BEFORE US
      A.     City & Borough of Juneau v. Thibodeau
             Before the Commission’s creation an Alaska Workers’ Compensation
Board decision could be appealed to the superior court, and a party dissatisfied with the
superior court’s final resolution of the case then could appeal to this court.3 Construing
the appellate rules, we decided in Thibodeau that “a decision of a superior court, acting
as an intermediate appellate court, which reverses . . . the decision of an administrative
agency and remands for further proceedings, is a non-final order of the superior court.”4




      1
            595 P.2d 626 (Alaska 1979), disavowed on other grounds by State v. Alex,
646 P.2d 203, 208 n.4 (Alaska 1982).
      2
             Id. at 629.
      3
            Cf. Municipality of Anchorage v. Anderson, 37 P.3d 420, 420-21 (Alaska
2001) (dismissing appeal because superior court order was not final).
      4
             Thibodeau, 646 P.2d at 629.

                                           -2-                                       7111

              In 2005 the legislature created the Commission,5 a quasi-judicial agency in
the executive branch6 authorized to hear appeals from decisions of the Board,7 and gave
parties to a Commission decision the right to appeal a “final” decision to this court.8 The
legislature also authorized our review of other Commission orders “as provided by the
Alaska Rules of Appellate Procedure.”9
              In the case before us the Commission decided that its decision was final as
to some issues but not as to others and gave the parties notice that they could appeal to
this court those parts of the decision that were “final” but needed to petition for
discretionary review if they wanted review of the “non-final” portions of the order. The
injured worker appealed a “final” part of the decision. We ordered the parties to provide
supplemental briefing on the question of the finality of the Commission’s decision and
the applicability of the Thibodeau rule to the Commission’s decision.
       B.     Three-Step Presumption Analysis
              In addition to creating the Commission the 2005 amendments to the Alaska
Workers’ Compensation Act changed the causation standard for compensable injuries.10
At issue here is the effect of this change on the presumption analysis used to evaluate
workers’ compensation cases.



       5
              Ch. 10, § 8, FSSLA 2005.
       6
             See Alaska Pub. Interest Research Grp. v. State, 167 P.3d 27, 47 (Alaska
2007) (holding that the Commission is “a properly established quasi-judicial agency”).
       7
              AS 23.30.128(a).
       8
              AS 23.30.129(a).
       9
              Id.
       10
              See ch. 10, § 9, FSSLA 2005.

                                            -3-                                      7111

             1.     Pre-2005 analysis
             For work-related injuries before November 7, 2005,11 application of the
presumption of compensability consisted of three possible steps.12 At the first step the
employee was required to attach the presumption that the disability was work related by
“establish[ing] a preliminary link between his disability and his employment.”13 To
establish the link the employee was required to offer “ ‘some evidence’ that the claim
arose out of the worker’s employment.”14 If the employee attached the presumption, the
burden shifted to the employer to offer substantial evidence that either (1) provided an
alternative explanation excluding work-related factors as a substantial cause of the
disability, or (2) “directly eliminated any reasonable possibility that employment was a
factor in causing the disability.”15 We called the two methods of rebutting the
presumption “affirmative evidence” and “negative evidence.”16 An employer could rebut
the presumption by presenting a qualified expert’s testimony that the claimant’s work




      11
             Ch. 10, FSSLA 2005 (demonstrating effective date of November 7, 2005
for addressing the presumption).
      12
             DeYonge v. NANA/Marriott, 1 P.3d 90, 94 (Alaska 2000) (citing Osborne
Constr. Co. v. Jordan, 904 P.2d 386, 389 (Alaska 1995)).
      13
             Steffey v. Municipality of Anchorage, 1 P.3d 685, 690 (Alaska 2000) (citing
Stephens v. ITT/Felec Servs., 915 P.2d 620, 624 (Alaska 1996)).
      14
              Tolbert v. Alascom, Inc., 973 P.2d 603, 610 (Alaska 1999) (quoting
Gillispie v. B & B Foodland, 881 P.2d 1106, 1109 (Alaska 1994)).
      15
            Id. at 611 (quoting Williams v. State, Dep’t of Revenue, 938 P.2d 1065,
1072 (Alaska 1997)).
      16
             See Veco, Inc. v. Wolfer, 693 P.2d 865, 872 (Alaska 1985).

                                          -4-                                     7111

was probably not a substantial cause of the disability.17 The first two stages of the
analysis required the Board to consider the evidence in isolation without weighing it.18
             If the employer presented enough evidence to rebut the presumption, the
burden shifted back to the employee to prove the claim by a preponderance of the
evidence.19 Only at the third stage could the Board weigh the evidence.20 The employee
had to show by a preponderance of the evidence that work was a substantial factor in
causing the disability: to prevail, the employee had to show that “(1) ‘but for’ the
employment the disability would not have occurred, and (2) reasonable persons would
regard the employment as a cause and attach responsibility to it.”21




      17
            Bradbury v. Chugach Elec. Ass’n, 71 P.3d 901, 906 (Alaska 2003) (quoting
Big K Grocery v. Gibson, 836 P.2d 941, 942 (Alaska 1992)).
      18
              Tolbert, 973 P.2d at 610 (“For purposes of determining whether the
claimant has established the preliminary link, only evidence that tends to establish the
link is considered — competing evidence is disregarded.” (citing Veco, 693 P.2d at 869­
70)); Stephens, 915 P.2d at 624 (“[W]e examine the evidence tending to rebut the
presumption by itself in determining whether substantial evidence has been presented.”
(citing Veco, 693 P.2d at 869)).
      19
            Tolbert, 973 P.2d at 611 (citing La. Pac. Corp. v. Koons, 816 P.2d 1379,
1381 (Alaska 1991)).
      20
            Steffey v. Municipality of Anchorage, 1 P.3d 685, 691 (Alaska 2000) (citing
Stephens, 915 P.2d at 627).
      21
             Williams, 938 P.2d at 1072 (citing Fairbanks N. Star Borough v. Rogers &
Babler, 747 P.2d 528, 532 (Alaska 1987)).

                                          -5-                                      7111

             2.     The 2005 amendments
             In 2005 the legislature repealed and reenacted AS 23.30.010,22 modifying
the standard for compensability of work-related injuries. The legislature also included
in the reenacted statute a presumption analysis formulation. Alaska Statute 23.30.010(a)
now provides:
             Except as provided in (b) of this section,[23] compensation or
             benefits are payable under this chapter for disability or death
             or the need for medical treatment of an employee if the
             disability or death of the employee or the employee’s need
             for medical treatment arose out of and in the course of the
             employment.         To establish a presumption under
             AS 23.30.120(a)(1) that the disability or death or the need for
             medical treatment arose out of and in the course of the
             employment, the employee must establish a causal link
             between the employment and the disability or death or the
             need for medical treatment. A presumption may be rebutted
             by a demonstration of substantial evidence that the death or
             disability or the need for medical treatment did not arise out
             of and in the course of the employment. When determining
             whether or not the death or disability or need for medical
             treatment arose out of and in the course of the employment,
             the [B]oard must evaluate the relative contribution of
             different causes of the disability or death or the need for


      22
           Ch. 10, § 9, FSSLA 2005. The repealed provision simply stated:
“Compensation is payable under this chapter in respect of disability or death of an
employee.” Former AS 23.30.010 (2004).
             The legislature did not amend AS 23.30.120(a), the statutory subsection
containing several presumptions related to workers’ compensation, in 2005. See ch. 10,
FSSLA 2005. AS 23.30.120(a)(1) provides: “In a proceeding for the enforcement of a
claim for compensation under this chapter it is presumed, in the absence of substantial
evidence to the contrary, that . . . the claim comes within the provisions of this chapter
. . . .”
      23
             AS 23.30.010(b) is about mental injury and is not an issue in this case.

                                           -6-                                      7111

             medical treatment. Compensation or benefits under this
             chapter are payable for the disability or death or the need for
             medical treatment if, in relation to other causes, the
             employment is the substantial cause of the disability or death
             or need for medical treatment.
The legislature did not amend the definition of “arising out of and in the course of
employment” in AS 23.30.395 in 2005.24
             In Runstrom v. Alaska Native Medical Center the Commission construed
the new statutory language as changing the presumption analysis only at the second and
third stages.25 The Commission previously had interpreted the phrase “the substantial
cause” in AS 23.30.010(a) as meaning that a disability is compensable if, in comparison
to other causes, work is the most important factor in bringing about the disability.26 In
considering how the statutory change affected the second stage, the Commission in
Runstrom decided that the negative-evidence test from our prior cases — “directly
eliminat[ing] any reasonable possibility that employment was a factor in causing the
disability”27 — was now “incompatible with the statutory standard for causation”
because under the amended statute “employment must be more than a factor in terms of
causation.”28 It also determined in Runstrom that an employer can rebut the presumption




      24
             See ch. 10, §§ 66-67, FSSLA 2005 (amending AS 23.30.395).
      25
             AWCAC Dec. No. 150 at 6 (Mar. 25, 2011).
      26
             City of Seward v. Hansen, AWCAC Dec. No. 146 at 12-14 (Jan. 21, 2011).
      27
            Williams v. State, Dep’t of Revenue, 938 P.2d 1065, 1072 (Alaska 1997)
(emphasis added) (quoting Gillispie v. B & B Foodland, 881 P.2d 1106, 1009) (Alaska
1994)).
      28
             Runstrom, AWCAC Dec. No. 150 at 7 (emphasis in original).

                                           -7-                                     7111

by showing “that a cause other than employment played a greater role in causing the
disability . . . .”29
                The Commission decided here that the employer had met its burden through
expert opinions not identifying an alternative cause but nonetheless concluding that work
was probably not the substantial cause of the employee’s need for medical treatment.
The parties dispute whether the employer rebutted the presumption and in so doing raise
the question of the 2005 amendments’ impact on the second stage of the presumption
analysis both generally and as applied to this case.
III.    FACTS AND PROCEEDINGS
                Joseph Huit worked for Ashwater Burns, Inc. in 2010. Early in November
he was working on a remodel project, and as part of the job he removed a water-damaged
vanity from a bathroom. As he was carrying the vanity he scratched his abdomen on a
protruding drywall screw; he showed the scratch to some people at the job site, including
his brother Steven, but did not file a report of injury.
                Late that night Huit left Alaska to visit his daughter and grandchildren in
Florida. Near the end of the visit his daughter noticed the scratch, which she thought was
inflamed. Huit flew back to Alaska, stopping for a long layover in Seattle where he met
with his wife, who had been caring for her father in Oregon. His wife also noticed the
scratch and told him to watch it. According to Huit at some point later in November the
scratch appeared to heal.
                On Friday December 3 Huit felt ill at work, so he went to the emergency
room. After testing Huit the doctor diagnosed a likely “viral syndrome” and told Huit
to go home and rest but to return for a recheck if a fever still was present the following
Monday. Huit stayed home for about five days, but his symptoms did not improve —


        29
                Id.

                                             -8-                                     7111
they got worse. On December 9 he returned to the emergency room, where he was
diagnosed with endocarditis;30 he was hospitalized for several weeks while he received
antibiotics to treat the infection. The emergency room physician wrote that Huit had
“spontaneous endocarditis”31 and commented that he “had no history of IV drug abuse.”
Upon admission another physician noted that there was “[n]o evidence of significant
rash, erythema, breakdown, or bruising.” An infectious-disease doctor was consulted as
well; he observed that Huit’s blood cultures were “growing Staphylococcus aureus,” a
type of bacteria, and reported “[m]etastatic lesions to the spleen, kidneys and brain” as
well as “probable vegetation” on Huit’s heart.
             Studies of Huit’s heart showed progressive damage. An echocardiogram
in late December 2010 indicated “[m]oderate to severe aortic regurgitation,” when two
weeks earlier there had been only mild regurgitation and the valve opened well. By
January 2011 Huit had severe aortic regurgitation, and in February he underwent aortic
valve replacement surgery.
             Huit first thought about the possibility that the infection was work related
while he was hospitalized; he explained that after the doctors told him he had an
infection, he remembered the scratch and notified his employer. Ashwater Burns filed
a report of injury on December 21 and later controverted benefits, relying on a
cardiologist’s opinion formed after reviewing Huit’s medical records. One of Huit’s
treating physicians, Dr. Robert Bundtzen, an infectious-disease specialist, noted on
January 4, 2011 that an “abdominal abrasion” as described by Huit was “a possible portal


      30
             “Endocarditis” is an inflammation of the innermost layer of heart tissue;
bacterial endocarditis leads “to deformity and destruction of the valve leaflets of the
heart.” STEDMAN’S MEDICAL DICTIONARY 638,639 (28th ed. 2006).
      31
             “Spontaneous” medically is defined as “[w]ithout apparent cause; said of
disease processes or remissions.” Id. at 1814.

                                           -9-                                     7111

of entry” for the staph bacteria. Huit filed a written workers’ compensation claim for
several benefits, including temporary total disability and medical costs, in early January
2011.
              Ashwater Burns’s employer’s independent medical evaluation (EIME)
consisted of records reviews by two physicians: a cardiologist and an infectious-disease
specialist. Dr. Semler, the cardiologist, was skeptical that the scratch had happened or
that it was the cause of the infection because “[a] screw does not cause Staph[]ylococcus
infection. . . . [I]t has never been reported in medical literature that Staphylococcus grows
on screws.” He concluded: “The more likely medical explanation for the cause of the
bacterial endocarditis is unknown, not related to the speculated ‘scratch’ injury if it
occurred at all.” Dr. Leggett, the infectious-disease specialist, did not think the scratch
“was a more probable than not substantial cause of [Huit’s] S. aureus aortic valve
endocarditis.” He acknowledged that with this type of infection “[t]he portal of entry
may be rather insignificant, such as the alleged abrasion/scratch,” but thought the
infection was “just as likely to occur outside of work as at work.” He observed that the
source of the bacteria was Huit’s “own skin,” not the drywall screw. He also cited a
study showing that “13% of S. aureus bacteremias[32] had no identifiable source” and
concluded Huit fell into that category. Dr. Leggett wrote that it was unlikely “an infected
local wound” would be visible three to four weeks later. He did not think the outcome
would have been different if Huit had sought medical treatment when the scratch first
became inflamed.
              Because of the difference in medical opinions about causation, the Board
ordered a second independent medical evaluation (SIME), consisting of two


        32
              “Bacteremia” refers to the presence of live bacteria in the bloodstream. Id.
at 195.

                                            -10-                                       7111
examinations several months apart, one by Dr. William Breall, a cardiologist, and the
other by Dr. Francis Riedo, an infectious-disease specialist. Dr. Breall wrote that no
evidence in the medical records “indicate[d] that the scratch on the abdomen caused a
bacteremia”; to support this statement, he noted that the scratch “did not produce pus,”
the scratch “was not infected,” and “no culture [was] obtained from [the] scratch at the
time that it was red in appearance.” Dr. Breall concluded there was “no hard evidence
to indicate that Mr. Huit had an industrial accident” that caused the infection, but he
agreed with Dr. Bundtzen that the abdominal scratch was “a ‘possible’ portal of entry.”
                Dr. Riedo also thought it was possible but not probable that the “scratch
was the substantial cause of Mr. Huit’s endocarditis.” He thought it was “medically
reasonable that a scratch as described” could cause endocarditis, but he also thought a
scratch of that nature would still have been visible three to four weeks later. Dr. Riedo
did not think Huit’s work-related “injury or condition aggravate[d], combine[d] with or
accelerate[d] any condition whose treatment or disability [was] not otherwise” work
related. He concluded, “I do not believe that the purported scratch or infected scratch
was the source of Mr. Huit’s infection on a more probable than not basis.”
                Huit moved to Idaho and began treating with Dr. Dennis Stevens at the
Boise Veterans Administration (VA) beginning in 2013.33 Based on Huit’s reports the
VA medical staff thought the work-related scratch was the likely cause of Huit’s
endocarditis.
                The Board held a hearing solely about the compensability of Huit’s illness.
Several lay witnesses testified, but no doctors did. The focus of the testimony was the
witnesses’ observations of Huit’s abdominal scratch. At the conclusion of the hearing


      33
             Huit began receiving VA benefits after he developed endocarditis, although
he had been eligible for some time.

                                            -11-                                     7111
Huit argued that he had attached the presumption and his employer had not rebutted it
because the doctors the employer relied on could not eliminate work as a causal factor
in his need for medical treatment and subsequent disability. The employer argued it had
rebutted the presumption through expert reports that concluded work was not the
substantial cause of Huit’s endocarditis. It also contended Huit had not reported the
injury in a timely manner.
             To resolve the compensability question, the Board first considered whether
Huit had in fact scratched himself at work. The Board decided this was not a complex
medical question, and it applied the three-step presumption analysis to this factual
question.34 It found that Huit had attached the presumption through his testimony and
the testimony of his brother Steven. The Board determined that Ashwater Burns had
rebutted the presumption with a chart note from the hospital “that ‘[t]here is no good
portal of entry’ ” and with a medical opinion that the scratch would still have been
visible on December 9, the date Huit was admitted to the hospital. The Board then
weighed the evidence, giving the medical testimony less weight because doctors had
given completely different opinions about whether a scratch like the one Huit described
would still be visible when he went to the emergency room. The Board gave the lay
testimony more weight; it found that Huit had suffered a scratch in the course and scope
of his employment with Ashwater Burns.
             The Board then turned to the endocarditis. The Board found Huit had
attached the presumption the endocarditis was work related through Dr. Stevens’s
opinion that the scratch was “the only potential portal of entry for the infection.” The
Board interpreted prior Commission decisions as requiring Ashwater Burns to “present

      34
             See Sokolowski v. Best W. Golden Lion Hotel, 813 P.2d 286, 292 (Alaska
1991) (holding that worker was entitled to presumption of compensability on each
evidentiary question related to whether injury arose in course and scope of employment).

                                         -12-                                     7111

substantial evidence that a cause other than the scratch played a greater role in causing
the infection” to rebut the presumption. The Board examined different doctors’
testimony. It first considered Dr. Semler’s testimony; according to the Board, he “clearly
doubted the scratch occurred” but identified the “more likely medical explanation for the
cause of the bacterial endocarditis [was] unknown.” The Board did not consider an
unknown cause to be “substantial evidence that a cause other than employment played
a greater role in causing the need for medical treatment.” Both Dr. Breall, the SIME
cardiologist, and Dr. Leggett, the employer’s infectious-disease specialist, acknowledged
that a scratch like Huit described could be a portal of entry for the bacteria, but neither
doctor thought the scratch was more probably than not the substantial cause of the
endocarditis. Both doctors said it was just as likely the bacteria had entered Huit’s
bloodstream through another scratch or skin lesion, but neither doctor pointed to any
evidence that Huit had any such other problem. Again, the Board did not consider these
doctors’ opinions substantial evidence that a cause other than Huit’s work “played a
greater role in causing [his] need for medical treatment.” Finally, the Board summarized
Dr. Riedo’s testimony. Dr. Riedo agreed with the other doctors that the scratch was a
possible entry portal for the bacteria, but he thought the infection “was ‘impossible to
attribute to a single event.’ ” The Board did not consider this opinion substantial
evidence that could rebut the presumption because “if it is impossible to attribute the
infection to a single event, it cannot be attributed to a cause other than work.”
              The Board wrote that to rebut the presumption here, the employer needed
to produce more evidence than opinions that more likely than not, the scratch was not the
cause of the illness, because the doctors were unable to identify any other cause of the
illness. The opinions all considered the cause to be unknown, even though they agreed
the bacteria somehow had to have entered Huit’s bloodstream. Because the Board did
not consider any of the doctors’ opinions sufficient to rebut the presumption, it decided

                                           -13-                                      7111

that Ashwater Burns had not met its burden at the second stage of the presumption
analysis, making Huit’s illness compensable.
              The Board then engaged in an alternative analysis, in which it assumed the
employer had rebutted the presumption. The Board gave the most weight to the opinions
of Drs. Bundtzen and Stevens, Huit’s treating physicians. After again noting that several
doctors agreed the scratch was a possible entry point for the bacteria but doubted the
existence of the scratch, the Board gave less weight to the opinions of Drs. Breall, Riedo,
Leggett, and Semler because they “lacked important, credible evidence about the
existence of the scratch.” Based on the evidence and the weight assigned to it, the Board
concluded that Huit had proved by a preponderance of the evidence that his work injury
was the substantial cause of the endocarditis.
              Ashwater Burns appealed to the Commission, which affirmed in part and
reversed in part. The Commission agreed with the Board that Huit’s claim was timely
filed and that he had attached the presumption of compensability. The Commission
disagreed with the Board’s legal analysis related to rebutting the presumption, labeling
the Board’s interpretation of the Commission’s decision in Runstrom v. Alaska Native
Medical Center35 “a narrow reading” that was nonetheless “understandable, given
particular wording in that decision.” The Commission faulted the Board for requiring
the employer to produce substantial evidence that a cause other than employment was
the substantial cause of Huit’s endocarditis.       The Commission decided that the
presumption could be rebutted “through the presentation of substantial evidence that
work was not the substantial cause of a disability.” The Commission thought the
evidence “ruled out what was identified as the one-and-only potential work-related cause

       35
            AWCAC Dec. No. 150 at 7 (Mar. 25, 2011) (deciding that to rebut
presumption of compensability, employer should show “that a cause other than
employment played a greater role in causing the disability”).

                                           -14-                                      7111

of Huit’s disability, namely the scratch.” It quoted Dr. Riedo’s opinion that he did “not
believe on a more probable than not basis that the November 5, 2010 scratch was the
substantial cause” of the endocarditis. Dr. Riedo did not think it was probable because
of “the lack of any skin lesion noted just three to four weeks after the scratch.” The
Commission also cited Dr. Breall’s opinion that while it was possible that the scratch
might have been the portal of entry, it was not probable. The Commission thought that
these two opinions ruled out the scratch as the substantial cause of Huit’s endocarditis,
so it reversed the Board’s determination that Ashwater Burns had not rebutted the
presumption of compensability.
              The Commission also found fault with the Board’s alternative analysis.
Specifically the Commission was “unable to identify an opinion from any of the medical
experts . . . that the scratch was, to a reasonable degree of medical probability, the
substantial cause of [Huit’s] infection and endocarditis.” The Commission thought there
was “an insufficient connection between the evidence and the [B]oard’s conclusion.” It
reversed the Board’s alternative decision that Huit had proved his claim by a
preponderance of the evidence, and it remanded the case to the Board for “sufficient
findings, based on the record from the hearing . . . that would enable [the Commission]
to effectively review” the Board’s decision.
              The Commission informed the parties that its decision was final as to its
“affirmation of the [B]oard’s decision in part, reversal of the [B]oard’s decision in part,
and vacating the [B]oard’s decision in part.” It also said the decision was “non-final”
with respect to the “remand of the matter in part to the [B]oard.” The Commission then
notified the parties that the “final decision portion” of the decision became effective
“when distributed” unless one of them filed a request for reconsideration or an appeal.
The Commission advised the parties they could petition this court for review of the non-
final part of the decision.

                                           -15-                                      7111

              Huit appealed the part of the Commission’s decision about rebutting the
presumption of compensability. The parties jointly asked the Board to decide whether
it had jurisdiction “to consider the portion of the case remanded to the [B]oard” in light
of the appeal to this court. The Board decided that it had no jurisdiction over any part
of the case while an appeal was before this court.
IV.    STANDARDS OF REVIEW
              In an appeal from the Alaska Workers’ Compensation Appeals
Commission, we review the Commission’s decision rather than the Board’s.36 “We apply
our independent judgment to questions of law that do not involve agency expertise.”37
Interpretation of a statute is a question of law to which we apply our independent
judgment, interpreting a statute “according to reason, practicality, and common sense,
considering the meaning of the statute’s language, its legislative history, and its
purpose.”38 We do not mechanically apply the plain meaning rule but use a sliding scale
approach to statutory interpretation, in which “[t]he plainer the statutory language is, the
more convincing the evidence of contrary legislative purpose or intent must be.”39 We
review de novo the Commission’s legal conclusion that substantial evidence supports the


       36
            Humphrey v. Lowe’s Home Improvement Warehouse, Inc., 337 P.3d 1174,
1178 (Alaska 2014) (citing Shehata v. Salvation Army, 225 P.3d 1106, 1113 (Alaska
2010)).
       37
             Monzulla v. Voorhees Concrete Cutting, 254 P.3d 341, 343 (Alaska 2011)
(citing Barrington v. Alaska Commc’ns Sys. Grp., Inc., 198 P.3d 1122, 1125 (Alaska
2008)).
       38
            Louie v. BP Exploration (Alaska), Inc., 327 P.3d 204, 206 (Alaska 2014)
(citing Grimm v. Wagoner, 77 P.3d 423, 427 (Alaska 2003)).
       39
             Gov’t Emps. Ins. Co. v. Graham-Gonzalez, 107 P.3d 279, 284 (Alaska
2005) (quoting Muller v. BP Exploration (Alaska), Inc., 923 P.2d 783, 787-88 (Alaska
1996)).

                                           -16-                                       7111

Board’s factual findings by “independently review[ing] the record and the Board’s
factual findings.”40
V.	    DISCUSSION
       A.	    The Commission Decision Was Not A Final Decision For Purposes Of
              An Appeal As A Matter Of Right.
              The Commission called its decision as to three issues “final” and gave the
parties notice that the “final” decision parts would take effect unless they appealed to this
court. Huit appealed the Commission’s decision that Ashwater Burns had rebutted the
presumption of compensability. Under the rule in City & Borough of Juneau v.
Thibodeau — a superior court decision remanding a case to an administrative agency is
not a final judgment for purposes of appeal to this court41 — the Commission’s decision
would not be a final decision because the Commission remanded the case to the Board
for further factual findings.42 We ordered the parties to provide supplemental briefing



       40	
              Smith v. CSK Auto, Inc., 204 P.3d 1001, 1007 (Alaska 2009).
       41
             595 P.2d 626, 629 (Alaska 1979), disavowed on other grounds by State v.
Alex, 646 P.2d 203, 208 n.4 (Alaska 1982).
       42
               As the Board correctly recognized, the remand required it to consider the
same underlying issue raised in this appeal, namely the compensability of Huit’s
endocarditis. The Commission’s decision in this case was thus not akin to a partial final
judgment under Alaska Civil Rule 54(b), which permits a court to enter judgment “as to
one or more but fewer than all of the claims or parties” when multiple claims are
presented or multiple parties are involved. Cf. Humphrey v. Lowe’s Home Improvement
Warehouse, Inc., 337 P.3d 1174, 1178 n.5 (Alaska 2014) (noting severability of
attorney’s fees dispute from other issues and comparing Commission decision there to
partial final judgment). We have held that courts should sparingly apply Rule 54(b) to
avoid piecemeal appeals, noting “the law’s fundamental aversion” to those appeals.
Neese v. Lithia Chrysler Jeep of Anchorage, Inc., 210 P.3d 1213, 1223 (Alaska 2009)
(citing Cole v. State Farm Ins. Co., 128 P.3d 171, 173 n.2 (Alaska 2006)). The law is
averse to piecemeal appeals in the administrative context as well.

                                            -17-	                                      7111

on Thibodeau’s applicability to Commission decisions; we also invited the State to
participate as amicus curiae, which the State did.
              Ashwater Burns and the State correctly observe that Thibodeau does not
directly control when a Commission decision is final for purposes of appeal because
Thibodeau concerned appeals from superior court orders43 and the Commission is an
administrative agency rather than a court.44 Huit and Ashwater Burns both contend that
policy and our prior cases favor extending the rule in Thibodeau to Commission
decisions; they ask us to treat this case as a granted petition. The State sets out several
alternatives for determining when a Commission decision is final for purposes of appeal,
but it takes no position as to the best one because of the many roles it has in the workers’
compensation process.
              Our analysis begins with the statute’s language; AS 23.30.129(a) provides
in part: “Consistent with AS 22.05.010(b),[45] final decisions of the commission may be
appealed to the supreme court, and other orders may be reviewed by the supreme court
as provided by the Alaska Rules of Appellate Procedure.” The legislature did not in this
statutory subsection delineate what a “final decision of the commission” is, although it
clearly envisioned a system in which some Commission decisions are final and others
are not. Alaska Statute 23.30.128(e) requires the Commission to issue a written decision,
with specific features, within 90 days of the completion of briefing or oral argument in
an appeal from the Board; that written decision is called “the final commission decision.”


       43
              595 P.2d at 629.
       44
              Alaska Pub. Interest Research Grp. v. State, 167 P.3d 27, 47 (Alaska 2007).
       45
             AS 22.05.010(b) grants an appeal as a matter of right to this court “in those
actions and proceedings from which there is no right of appeal” to either the court of
appeals or the superior court.

                                           -18-                                       7111

              One possible construction of the statute is to consider any decision having
the characteristics set out in AS 23.30.128(e) a final decision for purposes of appeal.
This construction would be in accordance with the presumption that the same word used
twice in the same act has the same meaning,46 and it would make the entire decision in
this case appealable as a matter of right. But this construction is inconsistent with our
precedent about the finality of administrative decisions for purposes of appeal to the
superior court47 and appears to be at odds with the Commission’s normal practice when
remanding the entire case to the Board.48 Construing the two phrases as having the same
meaning would also be contrary to the rule of statutory construction that terms used in
statutes that have developed a specialized meaning through case law are presumed to
have that specialized meaning49 and the corollary that the legislature is aware of existing
case law when it enacts or modifies the law.50


       46
            ARCTEC Servs. v. Cummings, 295 P.3d 916, 923 (Alaska 2013) (citing
Fancyboy v. Alaska Vill. Elec. Coop., Inc., 984 P.2d 1128, 1133 (Alaska 1999)).
       47
             See, e.g., Ostman v. State, Commercial Fisheries Entry Comm’n, 678 P.2d
1323, 1327-28 (Alaska 1984) (holding that administrative decision is final when litigant
has no more opportunity to submit evidence or otherwise modify decision through
administrative process).
       48
               See, e.g., City & Borough of Juneau v. Olsen, AWCAC Dec. No. 184 at 20
(July 22, 2013); Titan Enters. v. State, Div. of Workers’ Comp., AWCAC Dec. No. 175
at 22 (Jan. 8, 2013).
       49
             Alaska Conservation Found. v. Pebble Ltd. P’ship, 350 P.3d 273, 281
(Alaska 2015) (citing Shea v. State, Dep’t of Admin., Div. of Ret. & Benefits, 267 P.3d
624, 633 n.33 (Alaska 2011)).
       50
             See Young v. Embley, 143 P.3d 936, 945 (Alaska 2006) (stating
presumption that legislature is aware of common law when enacting statutes); see also
Joseph v. State, 293 P.3d 488, 492 (Alaska App. 2012) (“[T]he legislature is presumed
                                                                        (continued...)

                                           -19-                                      7111

              We have held that the test for finality for purposes of judicial review of
administrative decisions “is essentially a practical one”51 that considers “whether the
agency has completed its decisionmaking process[] and whether the result of that process
is one that will directly affect the parties.”52 We have instructed that in deciding whether
an agency decision is final for judicial review, the superior court should “focus primarily
on the operational or ‘decretal’ language” in the decision.53 The inquiry should also
consider whether the litigants still have an opportunity “to submit evidence or alter the
decision through administrative means.”54 Because the Commission is a quasi-judicial
agency, we assume the legislature was aware of cases defining an agency decision’s
finality for purposes of judicial review when it enacted AS 23.30.12955 and intended a
“final” decision in that section to have the same meaning.




       50
             (...continued)
to be aware of pertinent court decisions when it amends a statute.” (citing Shea, 267
P.3d at 633 n.33)).
       51
            Crawford & Co. v. Baker-Withrow, 81 P.3d 982, 985 (Alaska 2003)
(quoting Matanuska Maid, Inc. v. State, 620 P.2d 182, 184 (Alaska 1980)).
       52
            Id. (quoting State, Dep’t of Fish & Game, Sport Fish Div. v. Meyer, 906
P.2d 1365, 1370 (Alaska 1995), superseded by statute on other grounds,
AS 18.80.112(b)).
       53
             Ostman v. State, Commercial Fisheries Entry Comm’n, 678 P.2d 1323,
1327 (Alaska 1984) (quoting Greater Anchorage Area Borough v. City of Anchorage,
504 P.2d 1027, 1030-31 (Alaska 1972), overruled on other grounds by City & Borough
of Juneau v. Thibodeau, 529 P.2d 626, 628-30 (Alaska 1979)).
       54
            Allen v. State, Dep’t of Revenue, Child Support Enf’t Div., 15 P.3d 743, 747
(Alaska 2000) (quoting Meyer, 906 P.2d at 1371).
       55
              See Young, 143 P.3d at 945.

                                           -20-                                       7111

              Two agencies are involved in the administrative process of a workers’
compensation decision rather than one, but they are integrally related, with Commission
decisions serving as legal precedent for both agencies.56 And while the Commission may
complete its decision-making process in cases like this one, when it remands the case to
the Board without retaining jurisdiction,57 the entire administrative decision-making
process is not complete if the remand permits further Board action that could change the
case’s outcome. On remand the parties here would have had the opportunity to alter the
decision through administrative means, either through argument or presentation of
additional evidence if the Board considered that necessary. As the Board recognized, the
remand considered essentially the same underlying issue that this appeal does. The
decretal language here contemplated further administrative proceedings by remanding
so the Board could make further findings. Thus under our precedent the case was not a
final administrative decision for purposes of judicial review.
              Construing “final decision of the commission” in AS 23.30.129(a) as
equivalent to a “final commission decision” in AS 23.30.128(e) would permit appeals
as a matter of right in cases that do not meet our precedents’ finality test and have not in
the past been labeled “final” by the Commission. A case remanded on all issues to the
Board is not “final” for purposes of judicial review because on remand the parties might
present evidence and make arguments that could change the decision. The Commission




       56
             See Alaska Pub. Interest Research Grp. v. State, 167 P.3d 27, 45 (Alaska
2007) (construing statutory provision that Commission decisions have force of legal
precedent unless reversed by this court).
       57
              The Commission may retain jurisdiction when it remands a case to the
Board. AS 23.30.128(d). No one questioned the Commission’s decision not to retain
jurisdiction in this case.

                                           -21-                                       7111

has not treated such cases as “final,”58 yet they meet the criteria of AS 23.30.128(e) as
long as they are in writing and contain the features set out in that subsection.
              Conversely, construing these phrases in the same manner could exclude
decisions that meet our precedents’ finality test. Alaska Statute 23.30.128(e) ties finality
to the Commission’s resolution of the merits appeal; a “final commission decision” is one
the Commission issues after “briefing on the appeal is completed or oral argument is
held.” But the Commission awards attorney’s fees under AS 23.30.008(d) as part of the
merits appeal, not as a separate case,59 so a decision about attorney’s fees might never
be “final” as the term is used in subsection .128(e).60 The Commission has not been
consistent in giving notice of appeal rights in its decisions about fees. In one case it
labeled a fee order “final” and gave the parties notice of their right to appeal;61 in another
case, it called its decision a “memorandum” decision and gave no notice to the parties
about finality or any appeal rights, even through discretionary review.62 We conclude

       58
               See, e.g., City & Borough of Juneau v. Olsen, AWCAC Dec. No. 184 at 20
(July 22, 2013); Titan Enters. v. State, Div. of Workers’ Comp., AWCAC Dec. No. 175
at 22 (Jan. 8, 2013).
       59
             See, e.g., Shehata v. Salvation Army, AWCAC Dec. No. 075 (Mar. 19,
2008) (attorney’s fees decision in AWCAC Appeal No. 07-021); Shehata v. Salvation
Army, AWCAC Dec. No. 063 (Dec. 20, 2007) (merits decision in AWCAC Appeal No.
07-021).
       60
             The Commission at times has treated its attorney’s fees decisions as
nonfinal. See Adamson v. Municipality of Anchorage, AWCAC Appeal No. 11-017,
Order on Motion for Reconsideration (AWCAC Order, Nov. 19, 2014) (denying
reconsideration of attorney’s fees decision because it was not a final decision but a
memorandum decision), filed in Adamson v. Municipality of Anchorage, S-15753.
       61
              See Shehata, AWCAC Dec. No. 075 at 11-12.
       62
              See Adamson v. Municipality of Anchorage, AWCAC Dec. No. 203 at 5
                                                                  (continued...)

                                            -22-                                        7111

that the terms used in AS 23.30.128(e) and AS 23.30.129(a) are not equivalent. Finality
for the Commission’s purposes can be distinct from finality for purposes of judicial
review; as the judicial body reviewing the Commission’s administrative decisions, we
will decide whether a Commission decision is final for purposes of judicial review by
applying prior case law.
             Our construction of the statute is consistent with the limited legislative
history concerning the Commission. As we have observed previously, the legislature’s
goals in creating the Commission were to make the workers’ compensation
administrative process more expeditious and consistent.63         Applying the rule in
Thibodeau to Commission decisions furthers these goals by permitting discretionary
review by this court when a case presents an important legal question but allowing the
administrative process to come to completion prior to an appeal as a matter of right. We
also have noted that the legislature wanted litigants appealing to the Commission to
retain “the same procedural rights of review that they had in the superior court.”64 The
rule in Thibodeau provides parties in the workers’ compensation system the same
process that existed prior to 2005; it also provides, as the State puts it, “an attractive
symmetry,” making the process more consistent with that of other agency appeals and
thus easier for unrepresented parties to follow. Applying Thibodeau also limits
piecemeal appeals65 and permits complete development of the agency record before


      62
            (...continued)
(Nov. 12, 2014).
      63
             Alaska Pub. Interest Research Grp. v. State, 167 P.3d 27, 39 (Alaska 2007).
      64
             Monzulla v. Voorhees Concrete Cutting, 254 P.3d 341, 347 (Alaska 2011).
      65
            See Neese v. Lithia Chrysler Jeep of Anchorage, Inc., 210 P.3d 1213, 1223
(Alaska 2009) (discussing policy against piecemeal review of cases).

                                          -23-                                      7111

judicial review.66 Thibodeau allows a party to preserve legal issues decided throughout
the case for review by this court after completion of the administrative process.67
             We are mindful that Commission decisions have the force of legal
precedent for both the Board and the Commission unless reversed by this court;68 the
State pointed to this feature of the statutory scheme as one policy consideration weighing
against application of Thibodeau to Commission decisions. Parties to an appeal like this
one, involving an important question of law and its application to the case, can petition
for review of a Commission decision if they are concerned about the Commission’s legal
analysis.69 And the legislature both provided a mechanism for the director of the
Division of Workers’ Compensation to appeal in Commission proceedings and permitted
the Division’s director to appeal a compensation order to the Commission when a party
in interest is not represented and the order “concerns an unsettled question of law.”70
These procedures should adequately protect against the risk that a legally erroneous
Commission decision would taint numerous cases.
             In light of the Commission’s notice to the parties here about their appeal
rights, Huit understandably appealed the Commission’s decision that Ashwater Burns
rebutted the presumption. Under the rule we adopt today, he did not have an appeal as
of right. But because this case involves an important question of law and immediate



      66
             Cf. Interior Paint Co. v. Rodgers, 522 P.2d 164, 169 n.7 (Alaska 1974)
(adopting rule that judicial review is limited to agency record).
      67
             595 P.2d 626, 631 (Alaska 1979).
      68
             AS 23.30.008(a); Alaska Pub. Interest Research Grp., 167 P.3d at 45.
      69
             AS 23.30.129(a); Alaska R. App. P. 402; Thibodeau, 595 P.2d at 631.
      70
             AS 23.30.127(a).

                                          -24-                                        7111

review will materially advance the termination of the litigation,71 we follow our
precedent to treat the appeal as a petition for review72 and grant it.
         B.	   The Commission Erred In Deciding That Ashwater Burns Rebutted
               The Presumption Of Compensability.
               The Commission reversed the Board’s decision at the second stage of the
presumption analysis and decided that Ashwater Burns had rebutted the presumption of
compensability.      The Commission thought the Board’s interpretation of the
Commission’s prior decisions was unduly “narrow” and wrote that “the presumption can
be rebutted through the presentation of substantial evidence that work was not the
substantial cause of a disability.” The Commission explained that the question the Board
needed to consider was “whether the medical evidence in this case ruled out employment
as the substantial cause of Huit’s infection and endocarditis.” Focusing on statements
in the SIME physicians’ reports, the Commission decided Ashwater Burns had provided
substantial evidence to rebut the presumption. The Commission relied on Dr. Breall’s
opinion that he could not say “there was ‘a reasonable medical degree of probability’ that
the scratch” caused Huit’s infection, even though Dr. Breall acknowledged it was
possible the scratch could have been where the staph bacteria entered Huit’s
bloodstream. It also quoted Dr. Riedo’s opinion that “[w]hile it is medically reasonable
that a scratch as described by Mr. Huit can cause this illness, it is possible but again not
probable” because no skin lesions had been documented three to four weeks after the
scratch.
               Huit argues that the presumption analysis as applied to his injury should be
no different from the presumption analysis before the 2005 statutory changes, set out in

         71
               See Alaska R. App. P. 402(b)(2).
         72
               See, e.g., Thoeni v. Consumer Elec. Serv., 151 P.3d 1249, 1253-54 (Alaska
2007).

                                           -25­                                       7111
Section II.B.1, because the legislative changes were meant to apply to claims where a
work injury aggravated a preexisting condition or injury and he had none. He maintains
that because there is no cause with which to compare the work-related scratch, Ashwater
Burns did not rebut the presumption because it could not rule work out as his infection’s
cause; in fact, the doctors all agreed the scratch was a possible entry point for the bacteria
that caused the infection.
              Ashwater Burns contends the Commission correctly decided that medical
opinions in the record rebutted the presumption and that to decide otherwise would
create an irrebuttable presumption. It asserts that because the statute now unambiguously
provides that compensation is payable only when, in relation to other causes,
employment is “the substantial cause”73 of a disability or need for medical treatment, at
the second stage it only needed to provide an expert opinion that the scratch was not the
substantial cause of the infection.
              As stated previously, we have yet to construe the 2005 amendments to the
Alaska Workers’ Compensation Act as they relate to the presumption analysis. The only
part of the presumption analysis at issue in this appeal is the second stage: Ashwater
Burns does not contest that Huit attached the presumption, and Huit did not ask us to
review the Commission’s decision about the third stage.
              Under the pre-2005 analysis the employer could rebut the presumption of
work-relatedness by presenting substantial evidence that either (1) provided an
alternative explanation that would exclude work-related factors as a substantial cause of
the disability, or (2) directly eliminated any reasonable possibility that employment was




       73
              AS 23.30.010(a).

                                            -26-                                        7111
a factor in causing the disability.74 An employer could rebut the presumption by
presenting a qualified expert’s opinion testimony that the claimant’s work was probably
not a substantial cause of the disability.75 That opinion had to be supported by
substantial evidence.76
              With respect to the second stage, AS 23.30.010(a) now provides that the
“presumption may be rebutted by a demonstration of substantial evidence that the death
or disability or the need for medical treatment did not arise out of and in the course of
the employment.”77 It then instructs: “When determining whether or not the death or
disability or need for medical treatment arose out of and in the course of the employment,
the [B]oard must evaluate the relative contribution of different causes of the disability
or death or the need for medical treatment.”
              We begin our analysis by examining the statutory language. The statutory
language does not require the Board to determine or even consider “the substantial
cause” at the second stage of the presumption analysis, but it does require the Board to
“evaluate the relative contribution of different causes” in deciding whether the disability
arose out of and in the course of employment. Here no other cause was identified as
contributing to Huit’s infection, so the Board did not need to evaluate the relative


       74
             Tolbert v. Alascom, Inc., 973 P.2d 603, 611 (Alaska 1999) (quoting
Williams v. State, Dep’t of Revenue, 938 P.2d 1065, 1072 (Alaska 1997)).
       75
            Bradbury v. Chugach Elec. Ass’n, 71 P.3d 901, 906 (Alaska 2003) (citing
Big K Grocery v. Gibson, 836 P.2d 941, 942 (Alaska 1992)).
       76
              Safeway, Inc. v. Mackey, 965 P.2d 22, 27-28 (Alaska 1998).
       77
              AS 23.30.395(2) defines “arising out of and in the course of employment”
as including “activities performed at the direction or under the control of the employer.”
No one disputes that Huit was engaged in work-related activities when he scratched
himself on the vanity, so this work-relationship aspect is not at issue.

                                           -27-                                      7111

contribution of different causes to the infection. The Board nonetheless was required to
consider whether Ashwater Burns had provided “a demonstration of substantial evidence
that the . . . disability or the need for medical treatment did not arise out of and in the
course of the employment.”78
              Ashwater Burns maintains that it did so through medical opinions that, on
a more probable than not basis, the scratch was not the substantial cause of the disability.
But the statute does not instruct the Board to make the determination of “the substantial
cause” at the rebuttal stage. And at no point does the statute explicitly equate “aris[ing]
out of and in the course of employment” with “the substantial cause.”79 While both
phrases are prerequisites for receiving workers’ compensation,80 they could be two
independent conditions rather than one, equivalent condition. We thus disagree with
Ashwater Burns’s contention that the statutory language in this regard is not ambiguous.
To resolve the ambiguity, we examine the legislative history to consider the degree to
which the legislature intended to modify the presumption analysis developed under the
prior causation standard.
              As Ashwater Burns points out, “the substantial cause” as a standard for
awarding compensation originated with the legislature’s desire to limit aggravation
claims. One principal reason the governor cited for proposing the 2005 Alaska Workers’
Compensation Act amendments was “increasing costs of maintaining the current


       78
              AS 23.30.010(a).
       79
              Id.
       80
              The first sentence of AS 23.30.010(a) establishes that “compensation or
benefits are payable under this chapter for disability . . . if the disability . . . arose out of
and in the course of the employment,” and the last provides that “[c]ompensation or
benefits under this chapter are payable for the disability . . . if, in relation to other causes,
the employment is the substantial cause of the disability . . . .”

                                              -28-                                         7111

system.”81 The legislature considered limiting the compensability of aggravation claims
as a means of reducing insurance costs.82 The Senate Judiciary Committee proposed
added language that would have narrowed the definition of “injury” to exclude from
coverage an “aggravation, acceleration or combination with a preexisting condition
unless the employment [was] the major contributing cause of disability or need for
medical treatment.”83 According to Paul Lisankie, then the Director of the Division of
Workers’ Compensation, “the major contributing cause” would be the predominant cause
of the disability, or at least a 51% cause.84 He indicated that “the major contributing
cause” standard was meant to establish a “higher standard” for compensability than the
current law and that it was derived from Oregon law.85
              The House Labor and Commerce Committee removed this definition of
“injury,”86 but the change in defining “injury” was reinserted in the bill’s first conference




       81
              2005 Senate Journal 465.
       82
             See Minutes, Sen. Judiciary Comm. Hearing on S.B. 130, 24th Leg., 1st
Sess. 10:38-10:42 (Apr. 7, 2005) (testimony of Paul Lisankie, Director, Div. of Workers’
Comp.) (testifying that the “impetus” of the amendment excluding some aggravation
claims was “decreasing the cost of insurance premiums”).
       83
              Id. (amendment proposed by Chair Seekins and moved by Senator
Huggins).
       84
             Testimony of Paul Lisankie, Director, Div. of Workers’ Comp. at 10:37­
10:42, Hearing on S.B. 130 Before the Sen. Judiciary Comm., 24th Leg., 1st Sess.
(Apr. 7, 2005).
       85
              Id. at 10:41:08-10:41:17.
       86
              H.C.S. C.S.S.B. 130 (L&C), 24th Leg., 1st Sess. (May 5, 2005).

                                            -29-                                       7111

committee version.87 The House did not adopt the conference committee version of the
bill.88 In the Free Conference Committee, Senator Gene Therriault proposed an
amendment specifically providing that compensation was not payable for aggravation
claims unless employment was “the major contributing cause” of the disability; that
amendment failed.89
             Senator Therriault then proposed an amendment that established the
language of AS 23.30.010.90 Senator Therriault indicated the amendment’s language was
developed with Assistant Attorney General Kristin Knudsen, who spoke to the
committee about the bill.91 Knudsen testified that the language about the operation of the
presumption was derived from prior cases and was not intended to change the way the
presumption analysis operated.92 She identified both tests in prior case law for
overcoming the presumption,93 and she indicated, in response to Senator Hollis French,

      87
             C.C.S. S.B. 130, 24th Leg., 1st Sess. (May 13, 2005).
      88
             2005 House Journal 2042-44.
      89
             Minutes, H. Free Conference Comm. Hearing on S.B. 130, 24th Leg., 1st
Spec. Sess. 5:40-5:42, 9:12-9:28 (May 20, 2005).
      90
             Minutes, H. Free Conference Comm. Hearing on S.B. 130, 24th Leg., 1st
Spec. Sess. 1:18-1:19 (May 21, 2005) (statement of Sen. Gene Therriault).
      91
             Statement of Sen. Gene Therriault at 1:19:20-1:20, Hearing on S.B. 130
Before the H. Free Conference Comm., 24th Leg., 1st Spec. Sess. (May 21, 2005).
      92
             Testimony of Kristin Knudsen, Assistant Att’y Gen. at 1:25-1:26, 1:38­
1:39, Hearing on S.B. 130 Before the H. Free Conference Comm., 24th Leg., 1st Spec.
Sess. (May 21, 2005).
      93
             Minutes, H. Free Conference Comm. Hearing on S.B. 130, 24th Leg., 1st
Spec. Sess. 1:35-1:39 (May 21, 2005) (testimony of Kristin Knudsen, Assistant Att’y
Gen.) (stating that the employer’s burden is “unchanged” and the employer “must
                                                                     (continued...)

                                          -30-                                      7111

that the language up through the last line — in other words, the language about
application of the presumption analysis — was “not intended in any way to restrict or
change the current standard for work relationship.”94 Knudsen and Senator Therriault
both told committee members that the language about attaching and rebutting the
presumption was derived from our case law,95 and comments of some committee
members indicate they understood the amendment as codifying the standards for
attaching and rebutting the presumption.96       The legislative history thus suggests
application of the presumption analysis was to remain intact; there is no indication the
legislature intended to change the manner in which an employer rebutted the
presumption.
               Based on the legislative history we conclude that the Commission’s
interpretation of the statute as abrogating the negative-evidence test from prior case law
was erroneous,97 and we overrule that part of the Commission’s Runstrom decision.98
We agree with the Commission’s earlier observation that an opinion establishing that a


      93
             (...continued)
eliminate the possibility of a work relationship or must point to the way [sic] to
overcome the presumption”).
      94
               Id. at 1:44-1:46.
      95
               Id. at 1:35-1:42.
      96
             Id. at 1:35-1:50 (statements of Sen. Gene Therriault, Sen. Hollis French,
and Rep. Eric Croft, and testimony of Kristen Knudson, Assistant Att’y Gen.).
      97
               See supra text accompanying notes 15-16.
      98
             We affirmed the Commission’s decision in Runstrom because the result in
that case was the same no matter how the statute was interpreted. Runstrom v. Alaska
Native Med. Ctr., 280 P.3d 567, 573 (Alaska 2012). We nonetheless made clear that we
considered the interpretation of AS 23.30.010(a) an “open question.” Id. at 573 n.16.

                                          -31-                                      7111

cause is not a substantial factor of the disability rebuts the presumption using either “a
substantial factor” or “the substantial cause” as a standard because something cannot be
“the substantial cause” of a disability if it is not a cause at all.99 We observe that
elimination of the negative-evidence test arguably made it harder for an employer to
rebut the presumption in those cases of medical uncertainty in which the underlying
condition is poorly understood.100
               We next consider whether Ashwater Burns’s evidence met either the
affirmative-evidence test or the negative-evidence test. Because there was no competing
cause in this case, we do not consider how the presumption analysis should be applied
when another possible cause, such as a prior injury, contributed to the disability. We
agree with Huit that when there is no competing cause, the standard for rebutting the
presumption is essentially unchanged from prior cases: the requirement in subsection
.010(a) that the Board “evaluate the relative contribution of different causes” when
assessing work-relatedness presupposes the identification of more than one cause.
               Under the amended statute, rebutting the presumption required Ashwater
Burns to show that Huit’s infection did not arise out of his employment. On the facts of
this case, to do this, Ashwater Burns needed to show that the work-related scratch could
not have caused the infection (the negative-evidence test) or another source of the
bacteria caused the infection (the affirmative-evidence test). It argues that because
experts gave the opinion that work was probably not the substantial cause of the


         99
               State, Dep’t of Corr. v. Dennis, AWCAC Dec. No. 036 at 10 n.26 (Mar. 27,
2007).
         100
             See Safeway, Inc. v. Mackey, 965 P.2d 22, 28 (Alaska 1998) (affirming
Board decision that employer rebutted the presumption when employer’s expert refuted
the employee’s theory of causation by testifying that no relationship had been established
between the alleged injury mechanism and the employee’s medical condition).

                                          -32-                                      7111

disability it provided this evidence. But, as we said in Safeway, Inc. v. Mackey, “merely
reciting the proper words as an opinion is not necessarily enough to rebut the
presumption of compensability, because the employer must provide substantial evidence
that the disability was not work-related.”101
              Considering first the negative-evidence test, we conclude that the doctors’
opinions do not meet this test; they do not show that the work-related scratch could not
have been the entry point for the bacteria that caused the infection. In fact the experts
indicated that bacteria can enter the bloodstream through minor scratches like one Huit
described, and Ashwater Burns conceded at oral argument before us that the scratch was
a possible entry point for the bacteria.102 Moreover the Commission cited the opinions
of Drs. Breall and Riedo to support its determination that Huit attached the presumption.
              The doctors’ opinions here are distinct from the negative evidence offered
to rebut the presumption in Norcon, Inc. v. Alaska Workers’ Compensation Board103 and
Safeway, Inc. v. Mackey,104 two cases on which Ashwater Burns relies. In both Norcon
and Mackey, the employee established a causal connection, but it was eliminated by
expert-opinion testimony that no relationship existed between the alleged cause and the
disability. In Norcon, where long hours and their resulting stress allegedly caused a
worker’s ventricular fibrillation and resulting death, a doctor rebutted the alleged causal
connection by testifying that working long hours “is not recognized to be a risk factor

       101
            Id. at 27-28 (emphasis in original) (citing Big K Grocery v. Gibson, 836
P.2d 941, 942 (Alaska 1992)).
       102
            Ashwater Burns also agreed that the bacteria’s being present on Huit’s skin,
as opposed to being present on the drywall screw, was irrelevant for purposes of
determining work-relatedness.
       103
              880 P.2d 1051 (Alaska 1994).
       104
              965 P.2d 22 (Alaska 1998).

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for sudden cardiac death” and that there was no reasonable possibility “that the two are
related.”105 And in Mackey, where the worker alleged that her fibromyalgia developed
from earlier work-related injuries and repetitive stress, we recognized that the employer’s
doctor “testified that trauma and the development of fibromyalgia have not been reliably
related” and “rebutted the theories that [the claimant’s doctor] presented to link [the
claimant’s] work with her fibromyalgia.”106 In contrast the experts here indicated that
a scratch like the one Huit described could be an entry point. Because they did not rebut
the causation theory Huit’s doctors presented, their opinions did not meet the negative-
evidence test for rebutting the presumption.
              For the doctors’ opinions in this case to meet the affirmative-evidence
standard, they needed to provide substantial evidence ruling out the work-related scratch
as the source of the staph bacteria that caused Huit’s endocarditis by identifying another
explanation for the bacteria’s presence in Huit’s bloodstream.107 The Board carefully
considered each doctor’s opinion; we agree with the Board that none of the doctors
provided substantial evidence of another cause.
              “The mere possibility of another injury is not ‘substantial’ evidence
sufficient to overcome the presumption.”108 As the Board noted, Dr. Semler, the EIME
cardiologist who based his opinion “on the lack of evidence to support the alleged
scratch,” said the “more likely medical explanation for the cause of the bacterial
endocarditis is unknown.” We agree with the Board that an “unknown” cause is not
substantial evidence to rebut the presumption. The other EIME physician, Dr. Leggett,

       105
              Norcon, 880 P.3d at 1054.

       106
              Mackey, 965 P.2d at 28.

       107
              Tolbert v. Alascom, Inc., 973 P.2d 603, 611 (Alaska 1999).

       108
              Hoth v. Valley Constr., 671 P.2d 871, 874 (Alaska 1983) (per curiam).


                                           -34-                                      7111

gave the opinion that “an unidentified source” was the substantial cause of Huit’s
endocarditis, even though he acknowledged that “[t]he portal of entry may be rather
insignificant, such as the alleged abrasion/scratch.” Dr. Leggett listed other conditions
that might provide entry points for the bacteria, but as the Board observed, “he did not
identify [Huit] as having any of those conditions.” His opinion, like that of Dr. Semler,
was not substantial evidence rebutting the presumption.
              The SIME physicians’ opinions were similar. While both agreed that the
scratch could be an entry point for the bacteria, they refused to identify it as the
substantial cause of the infection, evidently because they lacked information about or
doubted the existence of the scratch. And like Drs. Semler and Leggett, Drs. Breall and
Riedo were unable to identify another entry point. Dr. Breall observed that “staph aureus
is ubiquitous” and can enter the bloodstream “in a susceptible individual from just about
any place.” He did not explain what would make an individual “susceptible,” and, absent
anything identifying Huit as particularly susceptible, this explanation does not rule out
the work-related scratch as the cause of the staph infection. Dr. Riedo also accepted that
the scratch Huit described could lead to endocarditis, but he thought the endocarditis was
“impossible to attribute to a single event.” He did not, however, point to other events
that contributed to it.
              The evidence the Commission cited was not substantial. The opinions
offered alternative theories of causation, but “the mere possibility” of a non-work-related
alternative is not sufficient to rebut the presumption.109 There was no direct evidence to
support the existence of another scratch or any other possible portal for the bacteria, and,


       109
              See Excursion Inlet Packing Co. v. Ugale, 92 P.3d 413, 419 (Alaska 2004)
(per curiam) (holding that employer did not rebut presumption because “there [was] no
direct evidence of [the alternative explanation] and it [was] inconsistent with” some
established facts).

                                           -35-                                       7111

as the Board observed, the EIME and SIME doctors did not have access to “the credible
lay testimony” about the existence of the scratch.110 We thus conclude the Commission
erred in deciding that Ashwater Burns rebutted the presumption of compensability.
       C.     There Is No Irrebuttable Presumption Here.
              Ashwater Burns maintains that Huit seeks to create an irrebuttable
presumption and that we have previously decided in cases of medical uncertainty that a
doctor’s opinion that the disability was not work related is adequate to rebut the
presumption. It argues that several doctors’ opinions met that standard, making the
Commission’s decision correct.        Huit denies seeking to create an irrebuttable
presumption, pointing out facts that might have rebutted the presumption, such as
evidence that he actually had “a similar injury away from work.”
              We agree with Huit that the difficulty Ashwater Burns faces is not a legal
hurdle, but a factual one. The uncertainty in Huit’s case revolved around where the
bacteria entered his bloodstream. The experts all agreed that staph caused his bacterial
infection, which in turn led to his need for medical treatment. They also indicated even
minor scratches can serve as entry points for bacteria. The uncertain causation in the
case was related to the existence of the scratch, as is evident from the experts’ reports;
the doctors expressed uncertainty about the existence of the scratch, not about whether
bacteria could enter the bloodstream through a scratch. The Board separately analyzed
the fact question related to the scratch and found that Huit had in fact been scratched at
work as he alleged. Ashwater Burns did not question the Board’s proceeding in this




       110
             Cf. Beauchamp v. Emp’rs Liab. Assurance Corp., 477 P.2d 993, 996
(Alaska 1970) (holding that “[c]ausation is not a matter lying exclusively within the field
of medical science” particularly when expert “lacked knowledge of relevant evidence
known to the Board”).

                                           -36-                                      7111

manner and did not appeal the Board’s resolution of this factual dispute to the
Commission.
              The additional cases Ashwater Burns relies on to support its argument about
irrebuttable presumptions are distinguishable.111 In Cowen v. Wal-Mart the medical
uncertainty involved whether physical activity could cause a breast implant to deflate.112
The employer’s doctor testified that no one knew whether deflation was “related to
physical activity,” but nonetheless gave the opinion, based on his experience, that work-
related activities were probably not a cause in the deflation of the employee’s implant.113
We agreed with the Board that from this testimony reasonable minds could conclude that
work-related physical activities were not a substantial factor in causing the employee’s
disability.114 Here, in contrast, the doctors agreed that Huit’s scratch could provide an
entry point for the staph and did not suggest an alternative entry point. Their opinions
that the scratch was, on a more probable than not basis, not the substantial cause of the
infection were related to doubts about the scratch’s existence.
              Likewise, in Bradbury v. Chugach Electric Ass’n an expert testified there
was no way to quantify how much external pressure was needed to rupture an
employee’s preexisting cyst.115 But the expert testified that sufficient trauma to do so
usually came from blunt trauma, that heavy lifting could not cause a rupture, and that the


       111
            We have already discussed two of these cases, Norcon, Inc. v. Alaska
Workers’ Compensation Board, 880 P.2d 1051 (Alaska 1994) and Safeway, Inc. v.
Mackey, 965 P.2d 22 (Alaska 1998).
       112
              93 P.3d 420, 425-26 (Alaska 2004).
       113
              Id.
       114
              Id. at 426.
       115
              71 P.3d 901, 907 (Alaska 2003).

                                           -37-                                      7111

employee’s work duties would not cause sufficient trauma to rupture the cyst.116 We
upheld the Board’s determination that a reasonable mind could conclude from this
evidence that work was not a cause of the cyst’s rupture because there was no evidence
of trauma and the expert directly refuted the employee’s theory that her work duties put
enough pressure on the cyst to rupture it.117
              An irrebuttable presumption is one “that cannot be overcome by any
additional evidence or argument because it is accepted as irrefutable proof that
establishes a fact beyond dispute.”118 Huit’s case does not involve an irrebuttable
presumption, even though Ashwater Burns’s task in rebutting the presumption became
more difficult after the Board made its finding about the scratch’s existence. In the end
Huit’s case is no different from cases we have previously considered, such as Firemen’s
Fund American Insurance Cos. v. Gomes119 or Excursion Inlet Packing Co. v. Ugale.120
In those cases the circumstances of the employees’ deaths were unknown, making the
employer’s task in rebutting the presumption a difficult one.121 But the uncertainty in this
case, as in Ugale or Gomes, is resolved through the use of the presumption of
compensability. With different facts Ashwater Burns may have faced a less difficult
task, but difficulty in finding and presenting additional evidence is not equivalent to
creating an irrebuttable presumption.


       116
              Id. at 906-08.

       117
              Id. at 903, 907-08.

       118
              See Conclusive Presumption, BLACK’S LAW DICTIONARY (10th ed. 2014).

       119
              544 P.2d 1013 (Alaska 1976).

       120
              92 P.3d 413 (Alaska 2004) (per curiam).

       121
              Id. at 419-20; Gomes, 544 P.2d at 1014, 1016.


                                           -38-                                       7111

VI.   CONCLUSION
             We REVERSE the Commission’s decision that Ashwater Burns rebutted
the presumption of compensability and REMAND to the Commission with instructions
to reinstate the Board’s award.




                                      -39-                                 7111

