                       IN THE SUPREME COURT OF TENNESSEE
                                  AT KNOXVILLE
                                          October 5, 2001 Session
                                            Heard at Gallatin1

                   STATE OF TENNESSEE v. JOHN R. FARNER, JR.

                     Appeal by permission from the Court of Criminal Appeals
                               Criminal Court for Sullivan County
                                No. 40,003 R. Jerry Beck, Judge



                       No. E1999-00491-SC-R11-CD - Filed December 11, 2001


The primary issue presented in this appeal is whether Tennessee law recognizes a co-perpetrator rule
which bars the defendant’s convictions for criminally negligent homicide on the basis that the
victims were co-participants in the drag race. After fully and carefully considering the record in this
case in light of the relevant authorities, we conclude that no rule of Tennessee law bars the
defendant’s convictions for criminally negligent homicide as a matter of law. We hold that causation
in criminal cases generally is a question of fact for a properly instructed jury, that a victim’s
contributory negligence is not a complete defense but may be considered in determining whether or
not the defendant’s conduct was a proximate cause of death, and that a jury’s determination of the
causation issue will be reviewed on appeal under the familiar sufficiency of the evidence standard
and not disturbed so long as the evidence is sufficient to support the jury’s determination. Because
the trial court in this case failed to provide the jury with an instruction on proximate causation, an
essential element of the offense, and because the jury was erroneously provided an instruction as to
criminal responsibility, a theory that the State now concedes is inapplicable, the defendant’s
convictions for criminally negligent homicide must be reversed.

        To prevent needless litigation and to promote judicial economy, we exercise our discretion
and address two other issues which will likely arise at any retrial – the propriety of Officer Farmer
testifying as an expert and the admissibility of the computer animated visualization of the accident.
We conclude that Officer Farmer may properly testify as an expert so long as the trial court is
assured that Officer Farmer’s opinions are based on relevant scientific methods, processes, and data,
and not upon mere speculation. However, we further conclude that the computer animated
visualization should not be admitted unless the State can establish that the visualization is based on
accurate and complete information and that it fairly illustrates the expert opinion of Officer Farmer
as to how the accident occurred. The convictions for criminally negligent homicide are therefore
reversed; the convictions for reckless endangerment with a deadly weapon, drag racing, and leaving

         1
          This case w as heard as part o f the O ctober 5, 2001 , S.C.A .L.E.S. (Supreme Court Advancing Legal Education
for Students) project in Gallatin, Sumner Coun ty, Tennessee.
the scene of an accident involving injury or death are affirmed. The judgment of the Court of
Criminal Appeals is affirmed in part, reversed in part, and the case is remanded to the trial court for
further proceedings consistent with this opinion.

    Tenn. R. App. P. 11; Judgment of the Court of Criminal Appeals Affirmed in Part;
                  Reversed in Part; Case Remanded to the Trial Court

FRANK F. DROWOTA , III, C.J., delivered the opinion of the court, in which E. RILEY ANDERSON,
ADOLPHO A. BIRCH, JR., JANICE M. HOLDER and WILLIAM M. BARKER, JJ., joined.

R. Wayne Culbertson, Richard A. Spivey, and Timothy Reid Wilderson, Kingsport, Tennessee, for
the appellant, John R. Farner, Jr..

Paul G. Summers, Attorney General & Reporter; Michael Moore, Solicitor General; Patricia C.
Kussmann, Assistant Attorney General; H. Greeley Wells, District Attorney General; and Teresa
Murray-Smith, Assistant District Attorney General, for the appellee, State of Tennessee.


                                             OPINION

                                           Background
        This case arose from a drag race between the defendant, John R. Farner, Jr., who was
driving his red Chevrolet Camaro, and the victim, Landon Baker, who was driving his white
Mitsubishi 3000 GT. The race, which occurred between 9:30 and 10:00 p.m. on March 20, 1997,
began at a Coastal Mart in the Colonial Heights neighborhood just south of Kingsport,
Tennessee. From the Coastal Mart, the defendant and Baker raced northbound toward Kingsport
on Fort Henry Drive, a four lane highway, for a distance of 3,432 feet, approximately six and
one-half tenths of a mile. The race ended when Baker lost control of his Mitsubishi in a curve
and collided with two other vehicles traveling toward Johnson City, in the southbound, oncoming
lanes of Fort Henry Drive, a Chrysler minivan and a green Volvo. Baker, and his passenger,
Christopher Bostrum, died as a result of the collision. The persons driving the other vehicles,
Teresa Gilliam and Priscilla Redwine, sustained serious injuries. The defendant’s car was not
physically involved in the collision. However, the defendant, and his alleged passenger, Steven
Moore, were each charged with two counts of vehicular homicide, two counts of aggravated
assault, one count of drag racing, and one count of leaving the scene of an accident knowing that
it involved death.

        The case proceeded to trial on these charges. At the close of the State’s proof, the trial
court entered a directed verdict in favor of Moore. With respect to Farner, the proof offered by
the State established that he instigated the drag race. Prior to Baker’s arrival at the Coastal Mart,
the defendant had asked Holly Harris, who was driving a Camaro, when they were going to race.
Harris responded, “Yeah, right.” As soon as Baker arrived, Harris overheard the defendant ask



                                                 -2-
Baker when he wanted to “run them.”2 Baker merely shook his head from side to side. When the
defendant left the Coastal Mart a short time later, he drove from the parking lot onto Colonial
Heights Road, stopped in the road, and revved his engine. Intending to leave by the same exit,
Baker waited for the defendant to pull up to the traffic light at the intersection of Colonial
Heights Road and Fort Henry Drive. However, the defendant remained in the middle of the road
some distance from the intersection, revving his engine. Eventually, Baker pulled onto Colonial
Heights Road ahead of the defendant and stopped at the red light, before turning right onto Fort
Henry Drive. The defendant immediately followed Baker, not yielding for oncoming traffic.

        Tracy Shipley, who was driving north toward Kingsport on Fort Henry Drive, approached
the intersection and saw a red Camaro with tinted side windows turn onto Fort Henry Drive
immediately behind a white car. Shipley said a Toyota pickup truck, approximately two car
lengths ahead of him in the right lane,3 had to swerve into the left lane to avoid hitting the red
Camaro. The cars then accelerated out of sight, but Shipley saw them again when he rounded a
curve, going side by side across the railroad trestle, with the red Camaro in the left, inside lane,
and the white car in the right, outside lane. Shipley estimated the cars were traveling in excess of
seventy miles per hour, and he did not see brake lights on either car. As Shipley stopped at the
Roadrunner Market near the railroad trestle, he heard a noise, which he believed was made by the
shifting of a ladder on the back of his truck, but a worker in the market commented that the two
cars had wrecked. Shipley arrived at the scene of the accident two to three minutes after leaving
the market. He saw a red Camaro sitting astride the white, dotted line, facing south, in the
direction of Johnson City. Someone jumped into the passenger side of the red Camaro, and it
then made a U-turn and drove north toward Kingsport at a high rate of speed. The car had tinted
side windows, but Shipley could not identify the person who jumped into the car nor could he say
for sure that the red Camaro was the same car he had seen earlier.

        Kregg Klingman, driving southbound on Fort Henry Drive toward Johnson City, was
south of the Texaco when he heard loud revving engines and saw two cars, side by side, going
northbound on Fort Henry Drive, toward Kingsport. Klingman estimated the vehicles were
traveling approximately eighty miles per hour, but he was unable to see the make, model, or
color of the cars. Although Klingman saw the cars disappear around the curve in his rearview
mirror, he did not recall seeing brake lights on either car.

      Elizabeth Reynolds, who worked at the Texaco service station on the corner of Fort
Henry Drive and Moreland Drive, was outside shortly before 10 p.m. on March 20, 1997 when


         2
           About 3 a.m ., follow ing th e accident, the defendant paged Harris. Although Harris did not recognize the
telephone number, she realized it was the defendant calling because the number “03" appeared at the end of the page.
The defendant previo usly had told H arris he would use “03" to identify himself if he paged her, explaining that he is a
Dale Earnhardt fan. When Harris returned the defendant’s call, she asked if he and Baker had be en racing. The
defendant replied , “No , not really. He took off and left me befo re I got to the Texaco.” The defendant denied seeing
the collision, explaining that he had seen only objects in the road and did not stop because he was scared.

         3
             The reco rd ind icates that police effo rts to locate the drive r of this Toyota truck were un successful.

                                                               -3-
she heard the roar of car engines and two cars traveling north toward Kingsport at a speed in
excess of 100 miles per hour. Although she could not determine the make or model of the cars,
Reynolds said the red car was in the left, inside lane, and the white car was in the right, outside
lane. Neither car applied its brakes as the cars disappeared around the curve. Reynolds almost
immediately heard a loud boom, and believing the vehicles had wrecked, she called for
emergency assistance.

       Anthony Bowman was stopped at a traffic light at the intersection of Moreland Drive and
Fort Henry Drive, headed south, when he heard loud revving engines. He saw two vehicles
approaching from the opposite direction, “neck and neck,” at a very high rate of speed, at least
seventy to seventy-five miles per hour. Bowman said the car in the left, inside lane near him was
red.

         Brian Bishop and Stanley Hodges, detectives with the Second Judicial Drug Task Force,
were parked near the intersection of Moreland Drive and Fort Henry Drive shortly before 10 p.m.
when they heard the sound of vehicles approaching at a high rate of speed from the Colonial
Heights area, heading toward Kingsport. Officer Bishop did not see the cars, but Officer Hodges
saw a red car in the left, inside lane, pass through the intersection, at approximately eighty-five
miles per hour. “Almost immediately”after the red car passed the officers heard the sound of
skidding and a collision. Both officers called for emergency assistance, reported the accident,
and proceeded to the scene. They searched the area for the red car, using a flashlight to look over
the side of the guardrail. Officer Hodges directed traffic at the scene for two hours but did not
see the red car return. However, he said the red car could have returned without his notice within
the first five minutes after the accident occurred because he was then attending the injured and
traffic had not yet become congested.

        Michael Taylor was driving south, intending to turn left at the intersection of Moreland
Drive and Fort Henry Drive, when he saw a white car and a red Camaro traveling toward him at a
high rate of speed. Taylor veered to the right, and he said the wind from the cars shook his van
as they drove past. Looking in his rearview mirror, Taylor saw sparks and brake lights from both
vehicles and almost immediately heard a loud pop. Taylor turned around, drove to the scene of
the accident, called for emergency assistance, and advised police to be looking for a red car.
Taylor was the only witness to place the white car in the left, inside lane and the red car in the
right, outside lane.

        Neither Teresa Gilliam, driver of the Chrysler Minivan, nor Priscillia Redwine, driver of
the green Volvo, remembered any details about the collision. Gilliam remembered driving south
on Fort Henry Drive toward Hammond Bridge, but her next memory was being inside an
ambulance. Redwine said she had just crossed Hammond Bridge when something to the left
attracted her attention. She remembered then seeing what appeared to be a white bullet heading
toward her. Her air bag deployed, and she was covered with glass and blood. Noticing an
unusual smell and fearing a fire, Redwine got out of the car.



                                                 -4-
        Gilliam, who sustained multiple injuries in the collision including, multiple broken bones
in her left leg and foot, a splintered right femur and crushed right foot, heel, and ankle, a broken
left elbow, and a laceration on her head, spent three weeks in the hospital, and received physical
therapy in her home for two months thereafter. At trial, Gilliam was still using a crutch to walk
and undergoing physical therapy. Gilliam’s prognosis as to further treatment or improvement
was uncertain. Redwine suffered lacerations on her head and left arm, bruises on her arm and
leg, embedded glass in her hand, and burns on her face from the air bag deployment. Her hands
are permanently scarred from the injuries she sustained.

       Officer Robert Dale Farmer of the Kingsport Police Department testified as an expert in
accident reconstruction. He was dispatched to the accident on Fort Henry Drive around 9:50
p.m. and arrived at the scene at 10:16 p.m. The vehicles involved in the collision had not been
moved. Redwine’s green Volvo with extensive front-end damage was resting against the
guardrail on the southbound shoulder of the road. Gilliam’s Chrysler minivan was sitting
crosswise in the southbound lanes facing the guardrail on the southbound shoulder. Part of the
white Mitsubishi was located against the guardrail on the southbound shoulder of the roadway.
Another part of the Mitsubishi was upside down in the left southbound lane.

        Officer Farmer testified that the collision occurred near the intersection of Fort Henry
Drive and Moreland Drive, north of the railroad bridge that travels underneath Forth Henry
Drive. This location is 3,432 feet, or approximately six and one-half tenths of a mile, from
where the drag race began. Officer Farmer located the point of impact by following yaw marks
from their beginning to where they ended with a gouge mark in the asphalt, Officer Farmer
explained that yaw marks are caused by a car sliding sideways while the wheels continue to
rotate forward. In this case, the yaw marks began just before the railroad bridge and continued
for 544 feet, ten inches. Officer Farmer opined that these marks establish that the Mitsubishi
traveled from the right northbound lane of Fort Henry Drive, across the left northbound lane,
striking Gilliam’s Chrysler minivan in the left southbound lane and Redwine’s green Volvo in
the right southbound lane. The impact of the Mitsubishi’s collision with the Chrysler minivan
caused a gouge mark in the pavement. At that point, the front wheels and engine compartment of
the Mitsubishi split from the passenger and rear portion of the car. The rear portion became
airborne, rotated, and struck the Volvo. From the white paint on the Volvo and the parts of the
Mitsubishi found lying across the Volvo’s front bumper, Officer Farmer determined that the
Mitsubishi initially struck the Volvo with its left rear undercarriage. The passenger compartment
and rear of the Mitsubishi landed on the southbound guardrail behind the Volvo. The front
wheels and engine compartment of the Mitsubishi came to rest upside down in the left
southbound lane.

       Officer Farmer said that Fort Henry Drive curves to the left at the railroad bridge and that
the speed limit where the accident occurred is 45 miles per hour. Officer Farmer calculated the




                                                -5-
speed of the Mitsubishi at 95.45 miles per hour when it began to yaw,4 and he determined that the
Mitsubishi was traveling 64.11 mile per hour when it struck the Chrysler minivan. He explained
that a car’s speed decreases during a yaw and that the Mitsubishi’s speed decreased by 31 miles
per hour during the 544 foot yaw, even though the evidence indicated that none of the cars
involved in the collision applied their brakes.

         Officer Farmer testified that the critical speed of a curve is the maximum speed any
vehicle, regardless of make, model, or year, can successfully traverse a curve in a particular lane.
Officer Farmer calculated the critical speed of the right lane of the curve in which the Mitsubishi
was traveling when it began to yaw is 73.88 miles per hour.5 Officer Farmer did not calculate the
critical speed of the left lane of the curve in which the defendant’s car was allegedly traveling,
and he conceded that the critical speed would be different but said it “would not vary a
tremendous amount.” Because of the absence of roadway evidence, Officer Farmer did not
calculate the speed of the defendant’s car or of the vehicles with which the Mitsubishi collided.

        Shortly after beginning the investigation, Officer Farmer directed Kingsport police
officers to locate the defendant. Although Detective Ralph Cline spent the rest of the night and
the early morning hours of March 21, 1997, searching, he was not able to locate the defendant or
the red Camaro. The defendant surrendered himself to the police at his lawyer’s office the
following afternoon at 5:30 p.m. There, Officer Farmer inspected the defendant’s car but found
no evidence indicating the defendant’s car had been physically involved in the collision.

        Officer Farmer gave a copy of his completed accident report and photographs of the area
and the accident scene to Professor Robert Neal Owen, director of the Advanced Visualization
Laboratory at East Tennessee State University. Professor Owen testified by stipulation as an
expert in computer visualization. He described computer animated visualization as a way of
telling a story by creating a “copy of reality” with a computer. Professor Owen explained that a
computer animated visualization differs from a computer simulation in that an animated
visualization utilizes the testimony of an expert to recreate the event, and as such, is an


         4
            Officer Farmer calculated this speed by locating the point at which the rear tires began tracking to the outside
of the front tires, determined the radius of the yaw, subtracted half of the track width of the car from the radiu s to
determine the speed of the center mass of the car, and entered these calculations, along with a drag factor or coefficient
of friction which he had computed by using a drag sled, into a speed formula that he obtained from the Institute of Police
Tec hno logy in Florida as part of his training in accident reconstruction. Officer Farmer testified that the formula had
been applied to accident investigations for several years, appeared in many instructional manuals that are used in police
training in acciden t reconstruction, and had been com mo nly u sed througho ut the Un ited States to determ ine speed.
Officer Farmer used this same procedure to calculate the speed at which the Mitsubishi was traveling when it collided
with the Chrysler minivan.
         5
           Officer Farmer calculated this speed by first measuring the chord, which is a straight line between the two ends
of the yaw mark, then calculating the middle ordinate, which is the distance from the center of the chord to the end of
the yaw ma rk. H e used the mid dle ordinate to calculate the circumference, and he calculated the coefficient of friction
or drag factor of the road with an instrument called a drag sled. From all this information, Officer Farmer calculated
the critical speed of the curve.

                                                            -6-
illustration of the expert’s testimony and opinion, while a simulation utilizes a computer to apply
the laws of physics, and as such, purports to be an exact duplication of the event. Professor
Owen’s laboratory had not previously created a computer animated visualization of an
automobile accident, but he said the creation process is similar, regardless of the event depicted.
Professor Owen used information provided by Officer Farmer to create this animated
visualization, including the make and model of the vehicles, the speeds at which they were
traveling, the physical characteristics of the roadway, such as size, shape and slope, and the
locations of the vehicles after the collision.

         Because Officer Farmer’s accident report stated that the cars were side by side at the
beginning of the railroad bridge, the animation shows the Camaro slightly in front of the
Mitsubishi at the beginning of the visualization. Professor Owen explained that, because the
Camaro had to be traveling slower than the Mitsubishi when it entered the curve to avoid a
collision, the Camaro had to be slightly ahead of the Mitsubishi at the beginning of the
visualization to be located beside the Mitsubishi at the railroad bridge. The animation shows the
Camaro traveling the curve at or below 73.88 miles per hour, which Professor Owen described as
the critical speed of the curve. Professor Owen was not aware that Officer Farmer had not
calculated the critical speed of the curve for the lane in which the Camaro was traveling, but he
opined, that, if the critical speed of the two lanes differed only by one or two miles per hour, the
accuracy of the animated visualization would not be significantly affected.

        The trial court admitted the computer animated visualization and the State played the tape
for the jury. The animated visualization portrayed the collision at three different speeds – full
speed, one-half speed, and one-quarter speed – and from five different viewpoints – that of an
overview and those of the Camaro, the Mitsubishi, the Chrysler minivan, and the Volvo. In all,
the video contained fifteen visualizations of the collision. Briefly summarized, the visualization
shows the Camaro in the left northbound lane traveling slightly ahead of the Mitsubishi which is
traveling in the right northbound lane. The Mitsubishi accelerates slightly, continues through the
curve, pulls even with the Camaro, which appears to slow down slightly at the beginning of the
railroad bridge. The Mitsubishi then begins to yaw near the end of the bridge, causing it to turn
sideways toward the southbound lanes. The Camaro continues through the curve in the left
northbound lane, accelerating out of the curve ahead of and just before the Mitsubishi yaws
across the left northbound lane and into the left southbound lane. The passenger side of the
Mitsubishi strikes the front of the Chrysler minivan, and the front portion of the Mitsubishi splits
from the rest of the car. The passenger compartment and rear portion of the Mitsubishi becomes
airborne and rotates, striking the front of the Volvo in the southbound right lane. The
visualization ends with the Mitsubishi striking the Volvo and the Camaro continuing in the
northbound left lane as the accident occurs behind it.

       Based upon this proof, the jury convicted the defendant of two counts of criminally
negligent homicide, two counts of reckless endangerment with a deadly weapon, one count of




                                                -7-
drag racing, and one count of leaving the scene of an accident involving death or injury.6 The
trial court sentenced the defendant as a Range I standard offender to two years on each count of
criminally negligent homicide and to two years on each count of reckless endangerment. The
trial court ordered the sentences on the felonies served consecutively, with concurrent sentences
for the misdemeanor offenses of drag racing and leaving the scene of an accident involving injury
or death, for an effective sentence of eight years.

        The defendant challenged his convictions and sentences on appeal, raising numerous
issues. Finding that double jeopardy considerations preclude dual convictions for reckless
endangerment under the circumstances of this case, the Court of Criminal Appeals vacated one of
the defendant’s convictions for reckless endangerment and thereby reduced his effective sentence
to six years. While finding that the trial court erred in admitting the computer-generated
visualization, the Court of Criminal Appeals nonetheless concluded that the error was harmless
beyond a reasonable doubt and did not require reversal. The Court of Criminal Appeals affirmed
the judgment of the trial court in all other respects and specifically rejected the defendant’s
assertion that Tennessee law recognizes a co-perpetrator rule which precludes his convictions for
criminally negligent homicide.

        The defendant sought permission to appeal to this Court, asserting, among other things,
that his convictions were barred by the co-perpetrator rule, that the trial court erred in allowing
Officer Farmer to testify as an expert, and that the trial court’s error in admitting the computer
animated visualization requires reversal. We granted the application for permission to appeal,
and without preventing the parties from raising additional issues pursuant to Tenn. R. App. P.
13(a), specifically requested that the parties focus at oral argument upon the following issue: Can
the defendant be held criminally responsible for the death of co-perpetrators?

        For the following reasons, we reverse the defendant’s convictions for criminally
negligent homicide and remand this case for a new trial on those charges. At the new trial,
Officer Farmer may testify as an expert so long as the trial court is satisfied that Officer Farmer’s
opinions are based on relevant scientific methods, processes, and data, and not upon mere
speculation. The trial court should not admit the computer animated visualization at the new trial
unless the State can establish that the visualization is based on accurate and complete
information and that it fairly illustrates Officer Farmer’s expert opinion of how the accident
occurred. In all other respects, the decision of the Court of Criminal Appeals is affirmed.


         6
          With respect to counts one and two of the indictment, the trial court instructed the jury as to vehicular
homicide and the lesser offenses of reckless homicide and criminally negligent homicide. The jury convicted the
defendant of the least serious o ffense, crim inally neg ligent hom icide. With respect to counts three and four of the
indictment, the trial court instructed the jury as to intentional and reckless aggravated assault, reckless endangerment
with a dea dly w eapon, and reckless endan germ ent. The jury convicted the defendant of reckless endan germ ent w ith
a dead ly weapon. W ith resp ect to coun t five, the trial court instructed the jury as to drag racing only, and the jury
convicted the defendan t of this o ffense. W ith resp ect to count six, the trial court instru cted th e jury with respect to
leaving the scene of an accident knowing death resulted from the accident and leaving the scene of an accident involving
injury or death. The jury convicted the defendant of the less serious offense.

                                                            -8-
                     Criminally Negligent Homicide: Co-Perpetrator Rule
       Historically, involuntary manslaughter was proscribed by the laws of this State and
defined as the unlawful killing of another, without express or implied malice, that occurs in the
commission of some unlawful act. See State v. Davis, 798 S.W.2d 268, 270-71 (Tenn. Crim.
App. 1990). Generally, any violation of a statute resulting in death constituted involuntary
manslaughter “if the violation of the statute [was] the proximate cause of death.” See State v.
Hale, 840 S.W.2d 307, 314 (Tenn. 1992) (stating the rule); Brown v. State, 201 Tenn. 50, 53, 296
S.W.2d 848, 849 (1956) (applying the rule to uphold a conviction for involuntary manslaughter
where a passenger in the defendant’s car was killed in a collision which occurred when the
defendant violated a statute by improperly passing a car at the crest of a hill); Osborne v. State,
512 S.W.2d 612, 618 (Tenn. Crim. App. 1974)(stating the rule).

        When the General Assembly enacted the Criminal Sentencing Reform Act of 1989,
involuntary manslaughter was replaced by the offense of criminally negligent homicide. See
Sentencing Commission Comments to Tenn. Code Ann. § 39-13-212; State v. Adams, 916
S.W.2d 471,473-74 (Tenn. 1995). The General Assembly supplied a simple definition for this
offense. “Criminally negligent conduct which results in death constitutes criminally negligent
homicide.” Tenn. Code Ann. § 39-13-212(a). To establish this offense, the plain language of the
statute requires the State to prove three essential elements beyond a reasonable doubt: (1)
“criminally negligent conduct” on the part of the accused; (2) that proximately causes (“which
results in”); (3) a person’s “death.” Tenn. Code Ann. § 39-13-212(a); See also Adams, 916
S.W.2d at 474; State v. Owens, 820 S.W.2d 757, 760 (Tenn. Crim. App. 1991). Criminal
negligence is further defined by statute as follows:

       a person . . . acts with criminal negligence with respect to the circumstances
       surrounding that person’s conduct or the result of that conduct when the person
       ought to be aware of a substantial and unjustifiable risk that the circumstances
       exist or the result will occur. The risk must be of such a nature and degree that
       the failure to perceive it constitutes a gross deviation from the standard of care
       that an ordinary person would exercise under all the circumstances as viewed
       from the accused person’s standpoint

Tenn. Code Ann. § 39-11-106(a)(4); see also State v. Clifton, 880 S.W.2d 737, 742-43 (Tenn.
Crim. App. 1994); State v. Butler, 880 S.W.2d 395, 397 (Tenn. Crim. App. 1994) (discussing
this definition).

        Having set out the elements of the offense of which the defendant stands convicted, we
turn to the defendant’s first argument on appeal – that Tennessee law precludes his conviction
of this offense because the victims were co-perpetrators in the underlying crime of drag racing.
As support for his assertion, the defendant primarily relies upon State v. Severs, 759 S.W.2d 935
(Tenn. Crim. App. 1988).




                                                -9-
        In Severs, the issue was whether the trial court should have dismissed the charge of
felony murder because the victim of the attempted larceny, rather than the defendant, killed the
defendant’s co-perpetrator. The Court of Criminal Appeals found that the trial court had erred in
refusing to dismiss the charge of felony murder. The intermediate court recognized that, to
support a conviction for felony murder at common law, “the killing must have been in pursuance
of, rather than collateral to,” the underlying felony. Severs, 759 S.W.2d at 938. The court in
Severs emphasized that the felony murder statute in Tennessee adopted this common law
formulation of the rule by requiring that the murder be “in the ‘perpetration’ or ‘attempted
perpetration’” of the underlying felony. Id. The intermediate court concluded that the
circumstances in Severs failed to satisfy the “in perpetration” requirement because “the death
resulted from an effort to thwart rather than to perpetrate the felony.” Id. The Court of Criminal
Appeals commented that “[a]ny extension of the meaning of the statute to the current facts would
be in derogation of the common law definition of felony-murder.” Id. The Severs court
observed “that an extension of the felony murder rule beyond its common law limitation to acts
by the felon and his accomplice, to include the lethal actions of those not acting in pursuance of
the felonious scheme, is an appropriate action for the legislature . . . not the courts.” Id.

        Clearly, the Severs decision is an interpretation and application of the felony murder rule
in Tennessee. It does not announce a generally applicable co-perpetrator rule as the defendant
suggests. Recently, in State v. Buggs, 995 S.W.2d 102, 106 (Tenn. 1999), this Court discussed
the felony murder rule and reaffirmed that, to constitute felony murder, the killing must be “in
pursuance of” the underlying felony offense. As support for the decision in Buggs, this Court
relied upon Severs. See Buggs, 995 S.W.2d at 106. Decisions narrowly interpreting the felony
murder rule, like Buggs and Severs, acknowledge that the felony murder rule “is a legal fiction in
which the intent and the malice to commit the underlying felony is ‘transferred’ to elevate an
unintentional killing to first-degree murder.” Buggs, 995 S.W.2d at 107; See also State v. Pierce,
23 S.W.3d 289, 296 (Tenn. 2000). The rationale which underlies these decisions does not apply
either directly or by analogy in this case. Criminally negligent homicide is not first degree
murder. It is instead the least serious homicide offense recognized by the laws of this State, and
there is no justification for applying to this offense a principle that was developed to limit the
extension of a doctrine that elevates unintentional killings to first degree murder. The Severs
decision applies only in the context of felony murder, and, as the Court of Criminal Appeals
recognized, is completely unrelated to the crime of criminally negligent homicide.

        Moreover, our research has revealed no other statutory support for the defendant’s
assertion that Tennessee law includes a co-perpetrator rule which bars his convictions for
criminally negligent homicide. Neither the language of the statute defining the offense, nor the
language of any other statute mandates recognition of such a rule. “The power to define what
shall constitute a criminal offense and to assess punishment for a particular crime is vested in the
legislature.” State v. Burdin, 924 S.W.2d 82, 87 (Tenn. 1996); Hale, 840 S.W.2d at 314; Hunter
v. State, 496 S.W.2d 900, 902-03 (Tenn.1972); Jones v. Haynes, 221 Tenn. 50, 53-54, 424
S.W.2d 197, 198, (Tenn. 1968); Woods v. State, 130 Tenn. 100, 106-07, 169 S. W. 558, 559-60
(1914). Indeed, the court in Severs refused to extend the felony murder rule beyond its common


                                                -10-
law reach because of its recognition that such an extension is solely within the authority of the
legislature, not the courts. Likewise, in the absence of statutory authority, we decline to adopt a
co-perpetrator rule as the defendant suggests.

        By relying upon the co-perpetrator rule, the defendant is essentially urging that the
negligence of a victim co-participant in a drag race is a complete defense if the victim’s negligent
conduct is a proximate cause of the victim’s death. The Court of Criminal Appeals recognized
that some state courts have accepted this argument and have refused to imposed criminal liability
upon a defendant for the death of a co-participant in a drag race. See Velazquez v. State, 561
So. 2d 347 (Fla. Dist. Ct. App. 1990) (refusing to uphold the defendant’s conviction for vehicular
homicide for the death of his co-competitor in a drag race and stating that the victim’s death was
caused by his own conduct rather than the defendant’s participation in the drag race); Thacker v.
State, 117 S.E.2d 913 (Ga. Ct. App. 1961) (dismissing an indictment for involuntary
manslaughter on the basis that the indictment failed to allege that the defendant caused the death
of his co-competitor in a drag race and stating that the victim’s conduct in losing control of his
car was the independent cause of his death); State v. Peterson, 526 P.2d 1008 (Or. 1974)
(adopting the dissenting opinion of an intermediate appellate court judge which reversed the
defendant’s conviction for manslaughter upon finding that the defendant’s conduct did not cause
the death of the victim, a passenger in the vehicle of the defendant’s co-competitor in a drag race,
because the victim was a “knowing and voluntary participant” in the reckless conduct);
Commonwealth v. Root, 170 A.2d 310, 314 (Pa. 1961) (reversing the defendant’s conviction of
involuntary manslaughter on the basis that the defendant’s conduct “was not a sufficiently direct
cause of the competing driver’s death to make him criminally liable therefore”).

        However, as the Court of Criminal Appeals recognized, the better-reasoned cases reject
this approach and uphold homicide convictions when the victim is a co-participant in a drag race.
These courts have emphasized that the central causation issue is a matter for a jury’s
determination, that the victim’s negligence is not a complete defense but may be considered in
determining whether the defendant’s conduct is a proximate cause of the victim’s death, and that
a jury’s determination of causation should not be disturbed on review by an appellate court
unless the evidence is not sufficient to support the finding.

         For example, in State v. Melcher, 487 P.2d 3 (Ariz. Ct. App. 1971), a jury convicted the
defendant of six counts of vehicular manslaughter. The deaths occurred when the automobile
with which the defendant was racing collided with a third vehicle, killing the co-competitor in
the drag race and five persons in the third vehicle. The trial court granted the defendant a new
trial, but the Arizona Court of Appeals reversed and reinstated the jury’s verdict. In so doing, the
Arizona Court rejected the defendant’s argument that he could not be found guilty because his
car did not collide with the other vehicle, stating “[i]t is obvious that the defendant can be
criminally responsible for the death of the other racing party . . . if the racing was the proximate
cause of that other party’s death.” Id. at 162.




                                                -11-
        In State v. McFadden, 320 N.W.2d 608 (Iowa 1982), the defendant was convicted of two
counts of involuntary manslaughter. His convictions arose from a drag race in which the
motorist racing the defendant lost control of his car and struck a third vehicle. A passenger in the
third vehicle and the defendant’s co-competitor died as a result of the collision. The defendant
argued that the evidence was insufficient to establish causation since his car was not physically
involved in the collision. The Iowa Supreme Court rejected this argument, stating:

       Viewing the evidence in the light most favorable to the State, we hold that the
       record contains substantial evidence that defendant’s participation in a drag race
       with [the victim] was a concurring proximate cause of the accident . . . .

McFadden, 320 N.W.2d at 617.

        Likewise, in State v. Plaspohl, 157 N.E.2d 579 (Ind. 1959), the trial court directed a
verdict in favor of the defendant on the basis that the victim, a passenger in the defendant’s car
during the race, was an active participant in the unlawful act which resulted in his death, and
under the law, he had assumed the risk of the result. The Indiana Supreme Court reversed,
relying upon the following general rule:

       Contributory negligence is not available as a defense or an excuse in a criminal
       prosecution; this doctrine has no place in criminal law, and it cannot in any degree
       purge an act which otherwise constitutes a public offense of its criminal character.
       Accordingly, the contributory negligence of a person injured or killed by the
       criminal negligence of another does not relieve the latter from criminal
       responsibility.

Id. at 580. The Court explained that this rule is supported by the “great weight of authority in
other jurisdictions”7 and is founded upon the following premise:

       It is a basic concept of our society that the life of every man is both divinely and
       humanly significant. Every death upon the highway is more than a statistic. It is a
       tragedy which affects not only the individual and his family, but all of society.
       And if death results from the reckless use of the highway, the fact that the
       deceased joined in the reckless activity does not negate the fact of the death, nor
       does it assuage the loss to the family of the deceased or the community.

               Reckless homicide is a crime committed against the state. Therefore,
       contrary to the rule in civil cases, the fact that the deceased victim was ‘an active
       participant in the unlawful act which resulted in his death,’ . . . does not bar an
       action against another for the wrong which he has committed against the peace
       and dignity of the state.


       7
           Id. at 581, n.2 (citing cases).

                                                -12-
Id. at 580-81.

        In Goldring v. State, 654 A.2d 939 (Md. Ct. Spec. App. 1995), the defendant was
convicted of three counts of involuntary manslaughter. The deaths resulted when the defendant’s
competitor in a drag race lost control of his car, struck and killed two bystanders, and then died
himself from the collision. The defendant’s car was not physically involved in the collision. In
rejecting the defendant’s claim that a participant in a drag race may not be held criminally liable
for the death of a co-participant, the Maryland court stated:

         we hold that [the defendant’s] conduct in competing in the drag race bore a
         sufficiently direct causal connection to [the co-participant’s] death to support [the
         defendant’s] conviction for involuntary manslaughter . . . .

Id. at 944. In so holding, the Maryland court also pointed out that the victim’s reckless conduct
does not relieve the defendant of criminal liability for his own reckless conduct. Id. See also
People v. Hansen 68 Cal. Rptr. 2d 897 (Cal. Ct. App. 1997) (upholding the defendant’s
conviction for involuntary manslaughter upon finding that the defendant participated in a game
of Russian Roulette with the victim who was killed during the game); Commonweath v. Atencio,
189 N.E.2d 223 (Mass. 1963) (upholding the defendant’s conviction for manslaughter arising out
of his participation in a game of Russian Roulette).8

        The general principles upon which these courts relied in permitting a jury to decide
whether criminal liability should be imposed upon a defendant for the death of his co-participant
in a drag race are reflected in and consistent with Tennessee law. For example, in Cole v. State,
512 S.W.2d 598 (Tenn. Crim. App. 1974), the defendants, brothers Raymond Cole and Paul
Cole, Jr., were racing, when Raymond’s automobile collided with a third vehicle during the race,
killing the driver. Both Raymond and Paul were convicted as principal offenders of involuntary
manslaughter, even though the car driven by Paul was not physically involved in the collision.
The Court of Criminal Appeals upheld the convictions, stating that the jury was justified in
believing that the victim’s death was the “natural or probable consequence” of the defendants’
conduct in operating their motor vehicles in such a reckless and unlawful manner on the public
highways. Id. at 601.



         8
           See also Coffelt v. State, 307 N.E.2d 497, 500 (Ind. Ct. App. 1974 ) (stating that the contributory negligence
of a victim is no t a defense to involuntary man slaughter but will exonerate the defendant if the victim’s negligence was
the sole ca use o f his or her o wn death ); State v . Cha stain, 960 P.2d 756 , 761 (Kan. 19 98) (stating that contributory
negligence of a victim is no defense in a criminal case but is a circumstance which the jury may consider in determining
whether the defendant’s conduct was or was not a proxim ate cause o f the victim’s dea th); People v. Tim s , 534 N.W.2d
675, 681 n. 6 (M ich. 1995 ) (citing cases w hich hold that a victim’s contributory n egligence is not a defense bu t is a
factor to consider in determining w hether the defendant’s cond uct caused the victim’s death and describing this rule as
“un iversal” am ong the states); People v. M oore, 631 N.W.2d 779 , 781 -82 (M ich. Ct. App. 2001) (stating that the
negligence of a victim in failing to wear seatbelts and using marijuana was not a complete defense but could be
considered in determining whether the defend ant’s conduct caused dea th).

                                                           -13-
        The decision in Cole illustrates that proximate cause, an essential element of criminally
negligent homicide,9 is generally established in Tennessee by showing that the victim’s death was
the natural and probable result of the defendant’s unlawful conduct. See e.g. State v. Barnes, 703
S.W.2d 611, 614-15 (Tenn. 1985); State v. Randolph, 679 S.W.2d 943, 947-48 (Tenn. 1984);
Fine v. State, 193 Tenn. 422, 429, 246 S.W.2d 70, 73 (Tenn. 1952); Letner v. State, 156 Tenn.
68, 75-76, 299 S. W. 1049, 1051 (1927); Copeland v. State, 154 Tenn. 7, 12, 285 S. W. 565, 566
(1926); Odeneal v. State, 128 Tenn. 60, 69, 157 S. W. 419, 420 (1913); State v. Richardson, 995
S.W.2d 119, 125 (Tenn. Crim. App. 1998); State v. Grose, 982 S.W.2d 349, 352 (Tenn. Crim.
App. 1997). The defendant’s unlawful act or omission need not be the sole or immediate cause
of the victim’s death. Letner, 156 Tenn. at 76, 299 S. W. at 1051. “[H]e is responsible if the
direct cause results naturally from his conduct. The same is true if the direct cause is an act of
the deceased himself reasonably due to defendant’s unlawful conduct.” Id. (emphasis added).10
This concept was reaffirmed in Fine:

         the act of the deceased, resulting in his death (not being corporally injured by the
         defendant), must have been the natural and probable consequence of the unlawful
         conduct of [the defendant].

193 Tenn. at 429, 246 S. W. at 73.11 Finally, a victim’s contributory negligence does not relieve
a defendant of criminal liability for his or her own criminally negligent conduct. See, e.g.,
Gentry v. State, 184 Tenn. 299, 305, 198 S.W.2d 643, 646 (Tenn. 1947)(holding that the trial
court did not err in charging the jury that the victim’s contributory negligence in driving while
intoxicated did not relieve the defendant of his guilt of involuntary manslaughter where the
defendant’s automobile caused the collision that killed the victim). However, a victim’s
contributory negligence may be considered in determining whether, under the circumstances, the
defendant’s criminally negligent conduct was a proximate cause of death, or whether the victim’s
conduct was an independent, intervening cause of death. See Copeland, 154 Tenn. at 11, 285 S.
W. at 566.

        In accordance with these well-settled principles of Tennessee law, we decline to adopt a
broad co-perpetrator rule which precludes imposition of criminal liability upon a defendant for
the death of a co-participant in a drag race. Consistent with the well-reasoned decisions from


         9
             See Adams, 916 S.W .2d at 474 ; Owens, 820 S.W.2d at 760.

         10
             See Delawder v . Com mo nw ealth, 196 S.E.2d 913, 915 (Va. 1973) (stating that an intervening act wh ich is
reaso nab ly foreseeable does not break the causal connection and holding that the conduct of the defendant and his co-
competitor in a drag race co ncu rrently caused the victim’s death, even though the co-competitor struck the defendant’s
car, causing him to lose control and hit the victim).
         11
            Contrary to the defendant’s argum ent, there is no “wo unding” requirem ent in Ten nesse e law , as this
quotation well illustrates. Wh ile most hom icides are caused when a defendant m ortally wounds, or in the wo rds of Fine,
corp orally injures, the victim, not all homicides are caused in this fashion and there is no legal requirement of a
wounding. The legally required element is causation.

                                                          -14-
Arizona, Iowa, Indiana, and Maryland, we conclude that causation in criminal cases generally is a
question of fact for a properly instructed jury, that a victim’s contributory negligence is not a
complete defense but may be considered in determining whether or not the defendant’s conduct
was a proximate cause of death, and that a jury’s determination of the causation issue will be
reviewed under the familiar sufficiency of the evidence standard and will not be disturbed by an
appellate court so long as the evidence is sufficient to support the jury’s determination.

        We recognize that, while causation is an essential element of every homicide offense,
including criminally negligent homicide,12 it is not seriously disputed in most cases. See Wayne
R. LaFave and Austin W. Scott, Jr., Substantive Criminal Law, § 3.12 (a) (1986) (“In the ususal
case there is no difficulty in showing the necessary causal connection between conduct and
result.”). However, this is one of those rare cases in which causation was seriously and forcefully
disputed at trial and on appeal by the defendant’s reliance upon the co-perpetrator rule. (“It is the
unusual case–numerically in the minority, yet arising often enough to warrant considerable
attention by the courts–which gives difficulty in the area of causation. Id.).

        While the evidence is legally sufficient to support a jury’s finding that the defendant’s
conduct proximately caused Baker and Bostrum’s deaths, the jury in this case was not given an
instruction on proximate cause. It is well-settled in Tennessee that a defendant has a right to a
correct and complete charge of the law so that each issue of fact raised by the evidence will be
submitted to the jury on proper instructions. See State v. Garrison, 40 S.W.3d 426, 432 (Tenn.
2000); State v. Teel, 793 S.W.2d 236, 249 (Tenn. 1990). While harmless error analysis applies
when a trial court fails to include an instruction on an essential element of the offense, id., we are
unable to conclude that the error is harmless in this case. As stated, this issue was forcefully
disputed at trial. Closing argument focused upon this element.14 Both the State and the
defendant exhorted the jury to listen to the law given by the trial judge. However, the jury
instruction on criminally negligent homicide did not mention proximate cause.15 Given the


         12
              See Rogers, 992 S.W.2d 393; Tenn. Code Ann. § 39-13-212(a) (“which results in”).

         14
             For example, the State urged: “Look at the law the Judge gives you. Lo ok a t that. Proximate cause,
proxim ate result of conduct. What else are those two death s and those injuries but th e pro xim ate result of John Farner’s
conduct starting this race.” In final closing argum ent, the district attorney again asserted: “W hat was the proximate
result or a proxim ate cause o f this acc ident. The proximate cause was this gentleman right here, the defendant, agreeing
to, consenting to and taking part in that drag race. Had he not done it, we wouldn’t be here today.”

         The defendant’s closing argument urged: “Ladies and gentlemen, John Farner does not deny to you that he was
speeding that night. He does not deny to you that if you ch oose to call it a drag race, that’s w hat it was, okay?” “Now
ladies and g entlem en, she talks ab out pro ximate cause of things, prox imate cause. In a sense, that is the crux of this
case. Proximate cause. . . . And that’s the whole issue in this case is causation and proximate cause, ladies and
gentlemen. That’s what you’re going to have to, you’re going to have to consider. . . . Proximate cause, causation, who
caused the accident, that’s the thing you ’re go ing to have to loo k at.”
         15
              As to vehicular homicide, the jury was instructed that to find the defendant guilty, they had to find “that the
                                                                                                              (con tinued...)

                                                             -15-
particular circumstances of this case, the trial court’s failure to instruct on proximate cause,
standing alone, would most likely have been viewed as plain error requiring reversal. Cf. State v.
Howard, 30 S.W.3d 271 (Tenn. 2000) (reversing the defendant’s conviction because the trial
court failed to instruct on the natural and probable consequences rule). Reversal clearly is
appropriate, however, since the record also reveals another instructional error.

        The trial court instructed the jury as to criminal responsibility with respect to the
criminally negligent homicide charges. As the defendant asserts, and the State concedes on
appeal,16 the defendant cannot be found guilty pursuant to the criminal responsibility statute
because the victims did not commit homicide upon themselves. We agree. Certainly, one cannot
be convicted pursuant to a theory of criminal responsibility if there is no other person who is
guilty of the crime as a principal. See Pierce v. State, 130 Tenn. 24, 46, 168 S.W.851, 856
(1914). Accordingly, the trial court erred by instructing the jury as to criminal responsibility with
respect to the criminally negligent homicide offenses.

         Had the only error in this case been this improper instruction on criminal responsibility,
we may well have been able to conclude, as the State argues, that the error was harmless because
the evidence sufficiently establishes that Farner’s criminally negligent conduct in drag racing on
a public highway directly and proximately caused the victims’ deaths. However, as previously
stated, the jury was not properly instructed on proximate cause, the only element of the homicide
offense seriously disputed at trial. Accordingly, given the particular circumstances of this case,
we are unable to conclude that the instructional errors are harmless.

       In all fairness, we recognize that the instruction given by the trial court on criminally
negligent homicide was taken verbatim from Tennessee Pattern Jury Instruction: Criminal § 7.07,
which does not mention proximate cause.13 While the pattern instructions contain a general

          15
            (...continued)
killing was the proximate result of conduct creating a substantial risk of death or serious bodily injury to a person.” The
jury was further instru cted th at pro xim ate resu lt is “a resu lt, which is the natural and continu ous sequ ence,. . . a product
of an act occurring or concu rring with another, wh ich, had it not happened, the result would not have occurred.” The
jury did n ot convict the de fend ant of veh icular hom icide, and n o sim ilar instructions were giv en as to crim inally
negligent homicide, nor was the jury referred to the instructions on proximate result previously given.
          16
            In its brief the State concedes that the trial court should not have given a criminal responsibility instruction
with respect to the charges of criminally negligent homicide, stating, “Obviously neither Baker nor Bostrum committed
the offense of hom icide with respe ct to his own de ath.” The State asserts that the criminal responsibility instruction was
app ropriate and logically related to the reckless endangerment charges against Farner which arose from the injuries
sustain ed by Redw ine an d G illiam. The State asserts that the ev idence is sufficient to sup port the jury’s verdict as to
these offenses on either a theory of direct respo nsibility or on a theory o f crimina l responsibility for Baker’s actions.
The Court of Criminal Appeals agreed that the evidence is sufficient in this regard, and we affirm that portion of the
judgm ent of the C ourt of C riminal App eals.
          13
            Significantly, the pre-1 989 pattern jury in struction for invo luntary m anslaugh ter correctly instructed the jury
that to establish guilt, the state had to prove as one of the three elements of the offense “that death was the natural and
                                                                                                                  (con tinued...)

                                                               -16-
instruction on cause of death,15 there is no cross-reference in the criminally negligent homicide
instruction indicating that the general causation instruction should be given. Unless the pattern
instruction for each homicide offense includes a causation instruction, the general causation
instruction should be given. In the vast majority of cases, causation is not disputed, so omitting
this instruction would be considered harmless error. However, the fact remains that causation is
an element of every homicide offense, and the jury should be so instructed.16 In this case, the
trial court failed to instruct the jury as to causation, and the error was not harmless. Therefore,
the defendant’s convictions for criminally negligent homicide are reversed, and the case is
remanded for a new trial on these charges.

        In order to prevent needless litigation and to promote judicial economy, we exercise our
discretion and address two other issues which will likely arise at any retrial – the propriety of
Officer Farmer testifying as an expert and the admissibility of the computer animated
visualization of the accident. See Tenn. R. App. P. 13(b) (“[t]he appellate court . . . may in its


         13
           (...continued)
probable result of the defendant’s act.” Tenn. Pattern Instructions: Crim. § 20.06 (1988).

         15
              See Ten n. Pattern In structio ns: Crim. § 42 .14 (2 001 ).
         16
          The current pattern instruction on causation appears to have been drawn from the lead ing case s on the subject,
but many of those cases date back to the early 1900's, so the language certainly could be clarified. We recommend that
the Commission consider supplementing the current causation instruction with the following or similar language:

         Before the defendant can be convicted of any degree of homicide, the State must have proven beyond
         a reasonable doubt that the death of the deceased was proximately caused by the criminal conduct of
         the defendant.

         The proximate cause of a de ath is that cause which , in natural and continuous sequence, unbroken by
         any independent intervening cause, produces the death and without which the death would not have
         occurred.

         The defendant’s conduct need not be the sole or immediate cause o f death. The acts [or omissions]
         of two or more persons may work concurrently to proximately cause the death, and in such a case,
         each of the participating acts [or omissions] is regarded as a proximate cause. It is not a defense that
         the negligent conduct of the deceased may also have been a proximate cause of the death.

         However, it is a defense to homicide if the proof shows that the death was caused by an independent
         intervening act [or omission] of the deceased or another which the defendant, in the exercise of
         ordinary care, could not reasonably have anticipated as likely to happen. H owever, if, in the exercise
         of ordinary care, the defendant should reasonably have anticipated the intervening cause, that cause
         does not supersede the defendant’s origina l cond uct, and the defendant’s conduct is consid ered the
         proximate cause of death. It is not ne cessary that the sequence of events or the particular injury be
         foreseeable. It is only necessary that the death fall within the general field of danger which the
         defendant should have reasonably anticipated.

See 11 Wash. Pattern Jury Instructions: Criminal §§ 25.02 & 25.03 (2d ed. 199 4); State v. Perez-Cervantes, 6 P.3d 1160,
116 3 (W ash. 20 00); State v. Harris, 230 N.W .2d 203, 207 (Neb. 197 5).

                                                               -17-
discretion consider other issues in order, among other reasons: (1) to prevent needless litigation,
(2) to prevent injury to the interests of the public, and (3) to prevent prejudice to the judicial
process.”); see State v. Mixon, 983 S.W.2d 661, 673 (Tenn. 1999).


                                         Expert Testimony
        The defendant’s primary argument is that Officer Farmer did not have sufficient
knowledge of science, engineering, and math to qualify to testify as an expert witness. The
defendant points out that Officer Farmer has no college degree in any of these fields. While it is
not necessary to recount specifics, we note that Officer Farmer testified extensively about his
prior experience as a police officer investigating automobile accidents and about his training as
an accident reconstructionist. Officer Farmer admitted that he did not have a college degree and
that he had not taken geometry or physics in high school, but he emphasized that he had taken
three separate eighty hour courses in accident reconstruction and had learned the needed
mathematics and physics in these courses. He explained in detail the many factors he considers
in investigating an accident, including, the debris field, the point of impact, skid marks or yaw
marks on the roadway, eyewitness accounts of the accident, the angle of impact of the collision,
the position of the vehicles at the scene, the direction the vehicles were traveling, and the vehicle
having the right of way. Using a critical speed yaw, he calculates an adjusted radius and using a
drag sled, he calculates the coefficient of friction of the roadway. Officer Farmer testified that he
uses these calculations in conjunction with a speed formula to determine a vehicle’s speed.
Officer Farmer testified that he obtained this speed formula from the Institute of Police
Technology in Florida, that it also appears in many other accident reconstruction training
manuals, and that it is commonly used throughout the United States. See note 4, supra.

        At trial, the defendant did not object to the reliability of the speed formula or to Officer
Farmer’s understanding and explanation of the scientific basis of the formula. The defendant
attempted to raise this issue on appeal, but the Court of Criminal Appeals held that, in the
absence of a specific objection, the trial court did not err in allowing Officer Farmer to testify
based upon the formula. The Court of Criminal Appeals recognized that, had an objection been
interposed, the trial court would have required Officer Farmer to testify more specifically about
his understanding of the scientific basis of the formula. The Court of Criminal Appeals noted that
Officer Farmer testified about the reliability of the formula when he said that it is derived from
the Institute of Police Technology in Florida, that it appears in many accident reconstruction
training manuals, that it is commonly used throughout the United States, and that he had checked
calculations made with the speed formula against radar measurements of actual speed, finding
the formula calculations to be accurate.

       In general, questions regarding the admissibility, qualifications, relevancy and
competency of expert testimony are entrusted to the discretion of the trial court. McDaniel v.
CSX Trans., Inc., 955 S.W.2d 257, 263 (Tenn. 1997). Tennessee Rules of Evidence 702 and 703
govern the trial court’s exercise of discretion in this area and provide, respectively:



                                                -18-
       If scientific, technical, or other specialized knowledge will substantially assist the
       trier of fact to understand the evidence or to determine a fact in issue, a witness
       qualified as an expert by knowledge, skill, experience, training, or education may
       testify in the form of an opinion or otherwise.

       The facts or data in the particular case upon which an expert bases an opinion or
       inference may be those perceived by or made known to the expert at or before the
       hearing. If of a type reasonably relied upon by experts in the particular field in
       forming opinions or inferences upon the subject, the facts or data need not be
       admissible in evidence. The court shall disallow testimony in the form of an
       opinion or inference if the underlying facts or data indicate lack of
       trustworthiness.

While these rules require trial courts to “analyze the science and not merely the qualifications,
demeanor or conclusions of experts, the court need not weigh or choose between two legitimate
but conflicting scientific views. The court instead must assure itself that the opinions are based
on relevant scientific methods, processes, and data, and not upon an expert’s mere speculation.”
McDaniel, 955 S.W.2d at 265. The trial court’s determination is one of admissibility only. Id.
Once the evidence has been admitted, the defense is given broad latitude to test the validity of the
expert’s opinion on cross examination. Id. See also Tenn. R. Evid. 705. The weight to be given
the scientific expert evidence and the resolution of legitimate competing scientific views are
matters entrusted to the jury as the trier of fact. McDaniel, 955 S.W.2d at 265.

         Applying these rules to the facts of this case, we conclude that the trial court did not
abuse its discretion in allowing Officer Farmer to testify as an expert in accident reconstruction.
Officer Farmer testified about his knowledge, skill, experience, and training in the field.
Contrary to the defendant’s assertions at trial, the rules do not mandate that a person have a
college degree in order to testify as an expert. Education is only one of the qualifying criteria
listed in Rule 702. Officer Farmer testified about the reliability and general usage of the speed
formula that he employed in this case. In the absence of a specific objection, the trial court did
not err in failing to require Officer Farmer to testify in more detail about the scientific basis and
validity of the formula. At the new trial, the defendant will have an opportunity to test the
validity of the formula before the trial court determines admissibility. So long as the trial court is
assured that Officer Farmer’s opinions are based on relevant scientific methods, processes, and
data, and not upon mere speculation, the trial court should admit the evidence. McDaniel, 955
S.W.2d at 265. Of course, if the evidence is admitted, the defendant will have the opportunity to
test Officer Farmer’s methods and conclusions on cross-examination.

                              Computer Animated Visualization
       Because it will also no doubt be an issue at any new trial, we consider the admissibility of
the computer animated visualization. Computer generated evidence is an increasingly common
form of demonstrative evidence. Barbara E. Bergman and Nancy Hollander, 3 Wharton’s
Criminal Evidence, § 16:30 at 972 (15th ed. 1999) (“Wharton’s”). If the purpose of the computer


                                                -19-
evidence is to illustrate and explain a witness’s testimony, courts usually refer to the evidence as
an animation. See Kristin L. Fulcher, Comment, The Jury as Witness: Forensic Computer
Animation Transports Jurors to the Scene of a Crime or Automobile Accident, 22 U. Dayton L.
Rev. 55, 58 (1996); See, e. g., Pierce v. State, 718 So. 2d 806, 808 (Fla. Ct. App. 1997). In
contrast, a simulation is based on scientific or physical principles and data entered into a
computer, which is programmed to analyze the data and draw a conclusion from it, and courts
generally require proof to show the validity of the science before the simulation evidence is
admitted. Id.; see also Clark v. Cantrell, 529 S.E.2d 528, 535 n.2 (S.C. 2000).

         The record clearly reveals that the computer evidence admitted in this case is properly
classified as an animation, rather than a simulation. The evidence was admitted to explain and
illustrate Officer Farmer’s testimony about how the accident occurred.17 At the risk of stating the
obvious, we note that a computer animation offered to illustrate an expert’s opinion will not be
admissible unless the expert testimony is itself admissible pursuant to McDaniel and the
applicable Tennessee Rules of Evidence. See Pierce, 718 So.2d at 809.

        The proponent must further establish that the computer animation is a fair and accurate
depiction of the event it purports to portray. See Tenn. R. Evid. 901; State v. Williams, 913
S.W.2d 462, 466 (Tenn. 1996); Phillips v. F.W. Woolworth, Co., 867 S.W.2d 316, 318 (Tenn.
Ct. App. 1992); see also Wharton’s at 973; Pierce, 718 So.2d at 809; Cleveland v. Bryant, 512
S.E.2d 360, 362 (Ga. Ct. App. 1999); Hutchison v. American Family Mut. Ins. Co., 514 N.W.2d
882, 890 (Iowa 1994); Gosser v. Commonwealth, 31 S.W.3d 897, 903 (Ky. 2000); State v.
Harvey, 649 So. 2d 783, 789 (La. Ct. App. 1995); People v. McHugh, 476 N.Y.S.2d 721, 722
(N.Y. Sup. Ct. 1984); Clark, 529 S.E.2d at 536; Sommervold v. Grevlos, 518 N.W.2d 733, 737-
38 (S.D. 1994); Mintun v. State, 966 P.2d 954, 959 (Wyo. 1998).

        Because the jury may be so persuaded by its life-like nature that it becomes unable to
visualize an opposing or differing version of the event, the requirement that the animation fairly
and accurately portray the event is particularly important when the evidence at issue is a
computer animated recreation of an event. See, e.g. State v. Trahan, 576 So. 2d 1, 8 (La.
1990)(discussing a motion picture and stating “[t]he vivid impressions on the trier of fact created
by the viewing of the motion pictures will be particularly difficult to limit. . . .”); Clark, 529
S.E.2d at 536 (recognizing that if the portrayal is inaccurate, computer animations pose a high
potential to mislead the jury and to create lasting impressions that unduly override other
evidence); Sommervold, 518 N.W.2d at 737 (stating that because a video reconstruction has a
substantial impact on the jury which will tend to view it as true, to be admissible, such
reconstructions must be “nearly identical” to the actual event); Hinkle v. City of Clarksburg, 81
F.3d 416, 424-25 (4th Cir. 1996) (stating that because of its unusual persuasive value, to be
admissible, a computer animated visualization must be substantially similar to the actual event).



         17
           W e do not now decide the admissibility standards applicable to computer simulations offered as substantive
eviden ce. As a resu lt, we have not included in o ur discussion cases inv olving simulation s.

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        Like all evidence in Tennessee, a computer animation is subject to exclusion if “its
probative value is substantially outweighed by the danger of unfair prejudice, confusion of the
issues, misleading the jury, or by considerations of undue delay, waste of time, or needless
presentation of cumulative evidence.” See Tenn. R. Evid. 403; See also Pierce, 718 So. 2d at
809 (Fla. Ct. App. 1997); Gosser, 31 S.W.3d at 903; Clark, 529 S.E.2d at 536; Sommervold, 518
N.W.2d at 737. If a computer animated portrayal is inaccurate, its probative value decreases and
the likelihood that it will be subject to exclusion under Rule 403 increases. Like other evidence,
the admissibility of computer animations generally rests within the sound discretion of the trial
court, with the rules of evidence governing the exercise of the trial court’s discretion.

        Applying these rules to the facts in this record, we conclude that the trial court abused its
discretion in admitting the computer animated visualization in this case because it is not a fair
and accurate portrayal of the event depicted, and as a result, its probative value was substantially
outweighed by the danger of unfair prejudice.

        Although Officer Farmer was unable to make a determination as to the speed of the
defendant’s Camaro, the computer animation includes the Camaro and depicts it at various
speeds throughout the animation. For example, at the beginning of the animation, the Camaro is
depicted traveling ahead of the Mitsubishi. Later, the Mitsubishi overtakes the Camaro, and just
before the collision occurs, the animation shows the Camaro accelerating through the curve and
passing the Mitsubishi. Professor Owen testified that the Camaro was depicted at the critical
speed of 73.88 miles per hour.

        The depiction of the Camaro ahead of the Mitsubishi at the beginning of the animation is
inconsistent with the proof. The eyewitness testimony consistently described the cars as side-by-
side. Officer Farmer did not dispute or elaborate on these descriptions. Professor Owen
indicated that he did not base this portion of the depiction upon specific evidence, but he said the
cars must have been in this position to have later been side-by-side as described by the
eyewitnesses. However, Professor Owen was not qualified as an accident reconstructionist and
should not have based the animation upon his own assumptions, opinions, or conclusions. The
depiction is also inconsistent with Officer Farmer’s testimony conceding that he had not
determined the critical speed for the lane in which the defendant was traveling. While Officer
Farmer opined that it probably would not vary a tremendous amount, he testified that the critical
speed for the defendant’s lane of travel definitely would not have been 73.88 miles per hour.
Therefore, the animation is inaccurate in its depiction of the Camaro traveling at 73.88 miles per
hour. In addition, the animation’s depiction of the Camaro accelerating out of the curve is not
supported by the evidence, and in fact, seems to be inconsistent with Officer Farmer’s testimony
about the critical speed at which a vehicle could safely negotiate the curve. Finally, it is not clear
what speed the animation uses to depict the Chrysler minivan and the Volvo since there is no
evidence in the record indicating the speed of these vehicles prior to impact.

       Given that the computer animated visualization is based upon inaccurate and incomplete
information, we conclude that the trial court erred in admitting it at trial. We also note that the


                                                -21-
animation depicted the accident a total of fifteen times at various speeds. While we set no limit
on how many times a visualization may depict an event, we emphasize that trial judges must
carefully monitor such evidence and prevent cumulative presentation if it poses a substantial risk
of unfairly prejudicing the defendant. See Tenn. R. Evid. 403 and Tenn. R. Evid. 611. As
previously stated, animations generally have a substantial impact upon jurors, and that impact is
no doubt increased where jurors are allowed to view the animated visualization not once or
twice, but fifteen separate times.

        For all these reasons, we conclude that the trial court erred in admitting the computer
animated visualization. We emphasize, however, that the State may again seek admission of the
computer animated visualization at the new trial. Of course, as a prerequisite to admissibility,
the State must establish that the animation has been corrected to fairly and accurately illustrate
and explain the testimony of Officer Farmer. The trial court should be guided by the principles
discussed in this opinion when deciding whether to permit the introduction of the computer
animated visualization. We commend the trial court for clearly instructing the jury that the
animation is not itself evidence and was offered only to illustrate the testimony of the expert
witness. Such an instruction is appropriate whenever computer animation evidence is admitted.



                                               Conclusion
        For the reasons stated herein, the defendant’s convictions for criminally negligent
homicide are vacated and the case remanded for a new trial on these charges. At the new trial,
Officer Farmer may testify as an expert so long as the trial court is satisfied that Officer Farmer’s
opinions are based on relevant scientific methods, processes, and data, and not upon mere
speculation. However, the computer animated visualization of the accident is not admissible
unless the State first establishes that it has been corrected to accurately and fairly illustrate
Officer Farmer’s testimony. The trial court’s decision on admissibility shall be guided by the
principles discussed herein. The defendant’s convictions for reckless endangerment with a
deadly weapon, drag racing, and leaving the scene of an accident involving injury or death are
affirmed. Costs of this appeal are taxed to the State of Tennessee, for which execution may
issue if necessary.




                                              _______________________________________
                                              FRANK F. DROWOTA, III, CHIEF JUSTICE




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