                               In the

    United States Court of Appeals
                 For the Seventh Circuit
                     ____________________
No. 18-2442
UNITED STATES OF AMERICA,
                                                   Plaintiff-Appellee,
                                 v.

MARSHON SIMON,
                                               Defendant-Appellant.
                     ____________________

         Appeal from the United States District Court for the
                    Central District of Illinois.
             No. 16-CR-20077 — Colin S. Bruce, Judge.
                     ____________________

     ARGUED MAY 30, 2019 — DECIDED AUGUST 21, 2019
                ____________________

   Before FLAUM, MANION, and BARRETT, Circuit Judges.
     MANION, Circuit Judge. Police oﬃcers pulled Marshon Si-
mon over for failing to signal suﬃciently ahead of turning. A
drug-sniﬃng dog alerted on Simon’s car so oﬃcers searched
it. They did not find drugs, but they found a gun. The govern-
ment charged Simon with being a felon-in-possession. The
district judge denied Simon’s motions for recusal, suppres-
sion, and supplementation. Simon entered a conditional
guilty plea and received a sentence of 15 years. He raises a
2                                                    No. 18-2442

litany of issues on appeal. He argues the judge should have
recused himself because before he was a judge he supervised
a prior prosecution of Simon. He argues the judge should
have suppressed the gun because the oﬃcers lacked probable
cause to initiate the traﬃc stop and because they prolonged
the stop to allow for the dog sniﬀ. He argues the dog’s alert
was false and the dog was unreliable because he was improp-
erly trained. He argues the judge should have allowed him to
supplement the evidence after denial of suppression. Finally,
he argues one of his prior felonies should not have counted as
a predicate for purposes of the Armed Career Criminal Act.
Concluding the judge committed no reversible error in deny-
ing Simon’s motions, we aﬃrm.
                             I. Facts
    On the night of August 21, 2016, three police oﬃcers in a
“bike patrol unit” surveyed a particular section of Decatur, Il-
linois. Oﬃcers Jason Danner and Jamie Hagemeyer rode bi-
cycles. They sat behind a propane tank 145 yards from the in-
tersection of College and Green Streets. Oﬃcer Robert
Hoecker drove a squad car nearby.
    The bicycle oﬃcers saw a vehicle driven by Marshon Si-
mon leave the 1100 block of North College Street (five blocks
away) and drive toward them. As Simon approached the in-
tersection of College and Green Streets, he failed to signal at
least 100 feet before turning left from College onto Green. This
was according to the bicyclists’ testimony at the suppression
hearing, which the district judge credited. At the bicyclists’ re-
quest, Hoecker pulled Simon over at 10:26 p.m.
  Hoecker approached Simon’s car and made contact.
Hoecker introduced himself and told Simon the basic reason
No. 18-2442                                                 3

for the stop. Hoecker explained bicycle oﬃcers would arrive
and provide details. Simon questioned the basis for the stop.
Simon gave his driver’s license and proof of insurance to
Hoecker. According to Hoecker, Simon was cooperative and
polite, behaved normally, and was no more nervous than the
normal level of traﬃc-stop nervousness. Hoecker ran Simon
through the LEADS computer system and found he was val-
idly licensed and insured. Hoecker finished this check in less
than 2 minutes, before Danner and Hagemeyer arrived on
scene at about 10:29 p.m.
   Once Danner and Hagemeyer arrived they took over “pro-
cessing the ticket,” including some double-checking.
Hoecker’s role was to assist. Hoecker told Danner that Simon
had insurance and a valid license. Hoecker said he “didn’t
know if [Danner] wanted the dog or not.” (Appellant Br. at 8,
quoting Hoecker’s dashcam video.) Danner asked if Simon
had any criminal history. Hoecker then ran a criminal-history
check and found Simon had prior drug and weapon charges.
    Danner made contact with Simon. Danner testified Simon
appeared abnormally nervous. Danner testified Simon asked
about the violation and insisted he used his turn signal. Dan-
ner testified, “I observed him to pull his hand away from his
lap, and he was shaking pretty good, indicating to me that he
appeared nervous.” But Danner did not note this in the police
report and he did not mention this when discussing whether
to call a dog.
   Hagemeyer testified that while speaking briefly with
Hoecker he handed her Simon’s materials. She then went to
another squad car that had arrived on scene “to begin the
written warning.” Both Danner and Hagemeyer testified
about the various steps and processes a bike patrol unit
4                                                          No. 18-2442

completes as part of the mission instigated by a traﬃc viola-
tion, including monitoring and securing the scene, making
contacts with the driver, running computer checks, and writ-
ing out the warning or ticket.
    Danner decided to call a dog. He testified he decided to
call a dog at about 22:30:38 (10:30:38 p.m.) on the clock of
Hoecker’s dashcam, about 1 minute after Danner and Hage-
meyer arrived at the traﬃc stop. An oﬃcer called for the ca-
nine unit less than 4 minutes into the stop, when the ticket
was still being processed, according to the oﬃcers’ testimony.
   Canine handler Snyder arrived with Rex at the scene at
about 10:33 p.m. At that time, the traﬃc violation was still be-
ing processed, according to the oﬃcers’ testimony.1 Within a

    1 Here are excerpts on point from the bicycle patrol unit’s testimony:
Q: And when Officer Snyder arrived, was the traffic violation still being
processed?
Hoecker: Yes.
(Tr. Continuation of Suppression Hr’g, July 12, 2017, DE 44 at 19:1–19:3.)

Q: And do you recall approximately how long into the traffic stop it would
have been that [Officer Snyder, with Rex] arrived?
Danner: I believe it was around six or seven minutes.
Q: And were you still processing the traffic ticket at that time?
A: That’s correct.
(Id. at 50:19–50:24.)

Hagemeyer: From the time we arrived to the time Officer Snyder arrived
was three or four minutes.
Q: So a very short period of time?
A: Very short period of time.
Q: Were you still working on the traffic ticket at that time?
A: Yes.
Q: And still working on it diligently, correct?
A: [Nodding head up and down.]
No. 18-2442                                                   5

few seconds of walking around Simon’s car, Rex alerted.
Snyder took less than 20 seconds to prepare Rex, begin the
search, and confirm the alert. The time period from the begin-
ning of the stop to the alert was about 7 minutes. Hagemeyer
testified she had no part in conducting the actual dog sniﬀ.
She testified she “was writing the warning.” She confirmed on
cross-examination that she filled out the traﬃc warning, and
that Danner issued it to Simon. Defense counsel asked, “So
you were the one who filled out the date, time, name, address,
and birth date?” Hagemeyer answered, “I filled out the ma-
jority of it. I believe [Danner] signed it, though.”
    After the alert, Simon became angry and insisted there
were no drugs in his car. Danner asked Simon to step out of
his car. The police searched it. They did not find drugs, but
they found a gun. An oﬃcer drove Simon to the police station.
Danner handed Simon a traﬃc citation as he was released
from the station. Danner testified he filled out the citation.
                       II. Procedural posture
    Since Simon was a felon, the government charged him
with being a felon in possession of a firearm. The case was
assigned to Judge Bruce. Simon moved Judge Bruce to recuse
himself because he had served as the First Assistant United
States Attorney for the Central District of Illinois with super-
visory authority over a prior case against Simon culminating
in conviction. Judge Bruce denied the recusal motion.
    Simon moved to suppress the gun, arguing there was no
probable cause to stop his car, the police impermissibly ex-
tended the stop to get a dog on scene, and the dog was unre-
liable and improperly trained. Judge Bruce held an

(Id. at 87:24–88:7.)
6                                                 No. 18-2442

evidentiary hearing over parts of three days and heard testi-
mony from seven witnesses. He found the oﬃcers credible,
even if at times confused. He found the oﬃcers had probable
cause to think Simon committed a traﬃc violation, the oﬃcers
did not unreasonably prolong the stop, and Rex was a
properly trained and certified canine whose alert can lead to
probable cause. The judge denied the motion to suppress.
    Simon moved to supplement the record with additional,
unrelated traﬃc citations issued by Danner (to show the dif-
ferences in the oﬃcers’ handwriting to address the issue of
which oﬃcer wrote Simon’s citation) and a video made by a
defense investigator (to contradict the oﬃcers’ version of
events leading up to the traﬃc stop). The judge denied this
motion.
    Simon pleaded guilty conditioned on preserving his right
to appeal. He received an enhancement as an Armed Career
Criminal. The judge sentenced him to 15 years in prison, the
mandatory minimum.
   Simon appeals the denials of his motions to recuse, sup-
press, and supplement. He also appeals his qualification as an
Armed Career Criminal, arguing his prior conviction for at-
tempted armed robbery in Illinois in 2000 did not qualify as a
violent felony.
                        III. Analysis
A. Recusal
    Simon seeks remand because he claims Judge Bruce’s han-
dling of this case conveys the appearance of impropriety. Si-
mon does not claim Judge Bruce actually had or acted on any
unfair bias against Simon.
No. 18-2442                                                   7

    Simon argues Judge Bruce should have recused himself
under 28 U.S.C. § 455(a): “Any justice, judge, or magistrate
judge of the United States shall disqualify himself in any pro-
ceeding in which his impartiality might reasonably be ques-
tioned.” Below, Simon also sought recusal under 28 U.S.C. §
455(b)(3), but he no longer presses that on appeal.
    As the government agrees, we review a preserved § 455(a)
claim de novo. Cf. Fowler v. Butts, 829 F.3d 788, 793 (7th Cir.
2016) (holding § 455(a) can be vindicated on appeal); United
States v. Dorsey, 829 F.3d 831, 835 (7th Cir. 2016) (a preserved
§ 455(b) claim is reviewed de novo).
    To win recusal under § 455(a), a party must show a rea-
sonable, well-informed observer might question the judge’s
impartiality. United States v. Herrera-Valdez, 826 F.3d 912, 917
(7th Cir. 2016). In other words, the party must show an objec-
tive, disinterested observer fully informed of the reasons for
seeking recusal would “entertain a significant doubt that jus-
tice would be done in the case.” Id.
    Simon sought recusal early in the case on the ground that
Bruce served as First Assistant United States Attorney for the
Central District of Illinois from 2010 through 2013. During
that time, the government charged Simon with violating 21
U.S.C. §§ 841(a)(1) and (b)(1)(B). Bruce supervised the AUSA
assigned to that case. Simon pleaded guilty and was sen-
tenced in 2012 and again (after a successful appeal) in March
2013. This prior criminal case involved occurrence facts sepa-
rate from those in the present case. But the prior case is di-
rectly relevant to this case because the conviction in the prior
case enhanced Simon’s sentence in this case as an Armed Ca-
reer Criminal.
8                                                   No. 18-2442

    Judge Bruce denied the recusal motion. He noted he could
not remember any participation in past prosecutions of Si-
mon. Judge Bruce observed that even if he did participate in
a past prosecution, he did not participate in the current pros-
ecution, “which consists of new charges, wholly unrelated to
those brought against [Simon] in the past.” (Text Order, Dec.
6, 2016.)
    Simon likens this case to United States v. Herrera-Valdez.
There, the government prosecuted a defendant for illegal
reentry after deportation. Before trial on the illegal-reentry
charge, defendant moved to disqualify Judge Der-Yeghiayan
because he had served as the District Counsel for the Immi-
gration and Naturalization Service when defendant was de-
ported. District Counsel Der-Yeghiayan’s name was listed in
several places in INS’s briefing supporting deporting. Judge
Der-Yeghiayan denied the motion to disqualify and defend-
ant appealed. We observed that 28 U.S.C. § 455(a) requires a
judge to “‘disqualify himself in any proceeding in which his
impartiality might reasonably be questioned.’” Herrera-Valdez,
826 F.3d at 917. We reversed the denial of disqualification,
concluding “a reasonable, disinterested observer could as-
sume bias from the fact that the judge presiding over the de-
fendant’s prosecution for illegal reentry was the same person
who ran the oﬃce that pursued, and succeeded in obtaining,
the removal order that is the source of his current prosecu-
tion.” Id. at 919. We noted this was particularly true given that
the linchpin of defendant’s case against the illegal-reentry
charge was a collateral attack against the removal order. The
judge need not have been actually involved in the prior case
or be actually biased in the subsequent case to trigger the re-
quirement to recuse under § 455(a).
No. 18-2442                                                            9

    But here, the prior case does not directly give rise to or un-
derly the present case. And here, Simon attempts no collateral
attack against the prior conviction. Simon’s 2011 conviction
was not, and could not have been, the linchpin to his defense
in this subsequent case. A defendant in a federal sentencing
proceeding may not collaterally attack a prior conviction used
to enhance his sentence, with an exception not relevant here.
See Daniels v. United States, 532 U.S. 374, 382–83 (2001); Custis
v. United States, 511 U.S. 485, 487 (1994). Any collateral attack
against the prior conviction under 28 U.S.C. § 2255 would
have been time-barred. So there was no possibility of Judge
Bruce adjudicating the merits of a collateral attack against Si-
mon’s 2011 conviction here. And consequently there was no
reason to think Simon might have declined to launch a collat-
eral attack against the 2011 conviction because he feared
Judge Bruce would not be receptive to such an attack, or
would punish him in the present case for making such an at-
tack.
    The prior and subsequent cases at issue in Herrera-Valdez
are directly related in a way the prior and subsequent cases at
issue here are not. A closer analogy to Herrera-Valdez is Si-
mon’s prior conviction under the supervision of First AUSA
Bruce and the proceedings for revocation of supervised re-
lease involving that prior conviction and the gun possession
on August 21, 2016. Simon’s prior conviction directly gives
rise to and underlies the revocation proceedings. So Judge
Bruce recused himself from them.2 As this relationship is not

    2Simon asserts Judge Bruce recused himself from the revocation pro-
ceedings (2:11-cr-20002). The government does not contest this assertion.
The docket for that case neither confirms nor denies the recusal. We take
Simon’s word for it.
10                                                    No. 18-2442

present between Simon’s prior case and the current felon-in-
possession case, there was no need for Judge Bruce to recuse
himself here.
    True, the prior conviction enhanced the sentence for the
present conviction under the ACCA. But this is mere happen-
stance. It is not the same kind of direct connection we found
problematic in Herrera-Valdez. Another distinction between
Herrera-Valdez and this case is that there, the future judge’s
name was on the briefs against the defendant, but here the
future judge’s name was not on the briefs. This is a relevant
consideration because it bears on public perception. We do
not consider this to be a controlling factor by itself, but it is
relevant.
     Judge Bruce did not err in refusing to recuse.
B. Suppression
    Simon raises a series of potential errors regarding the de-
nial of suppression. He argues there was no probable cause to
believe a traﬃc violation occurred, and therefore initiating the
stop was unconstitutional. He argues the oﬃcers unconstitu-
tionally prolonged the traﬃc stop. And he argues Rex’s alert
was false and Rex was improperly trained. “We employ a
mixed standard of review on motions to suppress, reviewing
the district court’s factual determinations for clear error and
de novo its ultimate determination about whether the police
had suﬃcient grounds to stop or search the individual.”
United States v. Rodriguez-Escalera, 884 F.3d 661, 667 (7th Cir.
2018) (internal quotation marks omitted).
1. Initiating the stop
   Simon argues the oﬃcers lacked probable cause to believe
he committed a traﬃc violation, so they had no probable
No. 18-2442                                                   11

cause to stop him. If Simon were right, then the court should
have suppressed the gun as fruit of the poisonous tree. The
Fourth Amendment protects against “unreasonable searches
and seizures.” U.S. Const. amend. IV. Whenever police stop a
car, the stop must satisfy the Fourth Amendment’s reasona-
bleness requirement. Delaware v. Prouse, 440 U.S. 648, 663
(1979). If a search or seizure violates the Fourth Amendment,
a court will generally exclude resulting evidence. United States
v. Wilbourn, 799 F.3d 900, 910 (7th Cir. 2015).
    Simon goes so far as to assert he did not commit a traﬃc
violation. He argues the government did not meet its burden
of proof to establish he actually committed a traﬃc violation.
But the government had no such burden. Whether Simon
committed a traﬃc violation is irrelevant for Fourth Amend-
ment purposes so long as the oﬃcers had probable cause to
think he did. United States v. Lewis, 920 F.3d 483, 489 (7th Cir.
2019) (“The oﬃcer is not the judge. Whether the driver actu-
ally committed a traﬃc infraction is irrelevant for Fourth
Amendment purposes so long as there was an objective basis
for a reasonable belief he did.”).
    Generally, the decision to stop a car is reasonable, and
comports with the Fourth Amendment, “where the police
have probable cause to believe that a traﬃc violation has oc-
curred.” Whren v. United States, 517 U.S. 806, 810 (1996). Prob-
able cause exists when “the circumstances confronting a po-
lice oﬃcer support the reasonable belief that a driver has com-
mitted even a minor traﬃc oﬀense.” United States v. Cashman,
216 F.3d 582, 586 (7th Cir. 2000). Probable cause is an objective
standard, based on the totality of the circumstances. Lewis, 920
F.3d at 489. If an oﬃcer reasonably thinks he sees a driver
commit a traﬃc infraction, that is a suﬃcient basis to pull him
12                                                    No. 18-2442

over without violating the Constitution. United States v.
Muriel, 418 F.3d 720, 724 (7th Cir. 2005).
    Here, Simon acknowledges the probable cause determina-
tion depends entirely on the credibility of the two oﬃcers on
bicycles who testified they saw him turn without signaling at
least 100 feet ahead. Simon levies many attacks on their cred-
ibility, urging us to reverse under the clear error standard. Si-
mon admits the clear error standard is very demanding. Un-
der this standard, we only reverse when, after reviewing the
record as a whole, we have a “definite and firm conviction” a
mistake has been made. United States v. Whitley, 249 F.3d 614,
621 (7th Cir. 2001). The district judge, after all, listened to the
testimony directly and observed the demeanor of the wit-
nesses. United States v. Garrett, 757 F.3d 560, 568 (7th Cir. 2014).
The district judge is in a much better position to evaluate cred-
ibility than we are. His credibility determinations are entitled
to special deference. We take Simon’s credibility attacks in
turn.
i. Phantom stop sign
    First, Simon argues Hagemeyer swore at the suppression
hearing that there was a stop sign at the corner of College and
Green, but she was demonstrably and indisputably wrong. Si-
mon argues this impugns her claim she saw the traﬃc viola-
tion.
    The judge directly confronted Hagemeyer’s mistake. He
noted Hagemeyer “was wrong about that detail.” (Order, DE
21 at 4.) The judge said he would take the mistake into account
in assessing Hagemeyer’s credibility. But the judge concluded
the mistake does not weigh heavily against her credibility be-
cause the detail “is not greatly important regarding the traﬃc
No. 18-2442                                                   13

oﬀense for which Defendant was pulled over” and because
“[i]t would not have factored in to [sic] determining whether
or not to issue Defendant a ticket for failing to signal his turn
within not less than 100 feet of the intersection.” (Id.) Hage-
meyer’s determination at the scene that Simon failed to signal
at least 100 feet before the turn was not informed by the pres-
ence or absence of a stop sign at the corner. In other words,
there were other reasons independent of the presence or ab-
sence of a stop sign for Hagemeyer to think Simon failed to
signal at least 100 feet ahead of turning. Indeed, the presence
or absence of a stop sign is irrelevant to estimating distances
or to the requirement to signal. The judge simply did not find
this mistake about a stop sign to be very important. So the
mistake did not significantly undermine the reliability of
Hagemeyer to perceive other facts that night. Moreover, her
mistake about the stop sign has no bearing on Danner’s testi-
mony that he saw Simon fail to signal suﬃciently ahead of
turning.
    And as for the possibilities Hagemeyer lied about the stop
sign, and this lie undermines her credibility about everything
else, Simon does not go quite so far. In his opening appellate
brief, he does not directly, unequivocally accuse Hagemeyer
of intentionally lying about the stop sign. And Simon oﬀers
no explanation for why Hagemeyer would have had any rea-
son to lie about it. We see no clear error here.
ii. Distances
    Second, Simon argues Hagemeyer and Danner were
wrong about the distance between their location and the in-
tersection of College and Green. They both testified the dis-
tance was 75 yards. But the distance was actually 145 yards.
The oﬃcers’ testimony was demonstrably and indisputably
14                                                 No. 18-2442

wrong by a wide margin. Simon argues the oﬃcers’ ability to
judge distance was the key to their claim Simon committed a
traﬃc violation. He argues their failure to estimate the dis-
tance between their location and the intersection correctly
makes their claims about the distance between the location of
Simon’s car when he activated his turn signal and the inter-
section wholly incredible.
    Again, the judge directly confronted the mistaken testi-
mony. The judge decided the miscalculation was “of little im-
port when it comes to credibility.” (Order, DE 21 at 3.) The
judge reasoned that the fact that both oﬃcers estimated the
distance at 75 yards does not indicate collusion because if they
wanted to connive it is much more likely they would have
used a number closer to the actual distance. They were too
wrong to be conspiring to lie.
    And as for the argument that the oﬃcers’ mistake about
this distance undermines the credibility of their estimate
about Simon’s signaling distance, the oﬃcers had other, spe-
cific indicia of the signaling distance beyond a raw estimate
of the distance from A to B. The time between signaling and
turning, the car lengths between signaling and turning, and
the lengths of the headlight beams bolstered the probable
cause to think Simon signaled too late and too close. The judge
concluded the mistake about the distance between the bicy-
clists’ location and the intersection shows nothing more than
that both bicyclists were wrong about that distance. We see no
clear error here.
iii. Photographs
   Third, Simon argues photographs introduced into evi-
dence show the unbelievability of the oﬃcers’ claims. Danner
No. 18-2442                                                  15

and Hagemeyer both testified they saw Simon’s car leave the
1100 block of North College, five blocks from their position.
But, Simon argues, the photographs speak for themselves,
and there is no way someone could see the make, model, or
color of a vehicle at that distance.
    The judge simply disagreed. He examined the photo-
graphs and listened to the testimony and concluded “it is pos-
sible for an average person, with good vision who is used to
working at night, such as Danner and Hagemeyer, to see a car,
in the dark, turn onto a street with its headlights on.” (Order,
DE 21 at 4.) We also examined the photographs and read the
testimony, and we do not have anything close to a definite
and firm conviction the judge made a mistake in this regard.
Sometimes a photograph is not worth a thousand words.
iv. Ghost writer
    Fourth, Simon argues the judge ignored the oﬃcers’ mis-
statements about who prepared the traﬃc ticket. Hagemeyer
testified “I was writing the warning.” She answered “yes” to
the question: “[Y]ou said that you filled out the traﬃc warn-
ing in this case?” When asked if she was the one who filled
out the date, time, name, address, and birth date, she testified
she “filled out the majority of” the ticket herself, but she be-
lieved Danner signed it. But other evidence showed she filled
out none of it. Danner filled out both the traﬃc citation (later
voided) and the warning (Simon received hours later).
   Simon accuses the judge of tying himself “into a pretzel to
avoid finding that the police oﬃcers could possibly have lied
or misrepresented facts … .” (Appellant Br. at 33.) But the
judge committed no such contortions. Rather, he addressed
the discrepancies directly. He combed through the testimony
16                                                              No. 18-2442

about the various steps in the process leading to handing a
driver a written ticket or warning. He noted there appeared
to be confusion and possibly contradiction between the oﬃc-
ers about who actually wrote the ticket. One source of confu-
sion seemed to be the word “processing.” The judge observed
Hagemeyer, Snyder, and Hoecker all testified Hagemeyer be-
gan “processing” the ticket, but “processing” a ticket involves
much more than just physically writing the ticket. The judge
also observed Hagemeyer’s testimony on this issue was more
specific. She testified, “I was writing the warning.” When
asked, “So you were the one who filled out the date, time,
name, address, and birth date?” she responded, “I filled out
the majority of it. I believe [Danner] signed it, though.”3
     The judge compared the warning Simon received—pur-
portedly filled out by Hagemeyer and signed by Danner—to
a diﬀerent warning definitely filled out and signed by Hage-
meyer on a diﬀerent date. The judge concluded the handwrit-
ing on the two warnings is diﬀerent and they likely were not
filled in by the same oﬃcer.
   But the judge noted Simon did not show the exemplar
warning to Danner or Hagemeyer during the hearing to cross-
examine them on who wrote Simon’s warning. The judge also


     3  In his order denying suppression, the judge characterized Hage-
meyer’s testimony on this point slightly incorrectly, and in favor of Si-
mon’s arguments. The judge wrote “Hagemeyer answered ‘yes’ to
whether she filled in the name, date, etc., but she stated that Danner signed
it.” (Order, DE 21 at 10.) Actually (according to the transcript) she did not
say “yes” in response to this question. She said, “I filled out the majority
of it. I believe [Danner] signed it, though.” But even giving Simon the ben-
efit of this characterization, the judge still did not find a significant credi-
bility problem.
No. 18-2442                                                    17

noted the testimony indicated Danner or Hagemeyer would
often start writing a ticket the other would finish. The judge
observed: “There are numerous possibilities as to why the dis-
crepancy exists, and without the oﬃcers being given the
chance to explain the discrepancy, the court cannot impute
improper conduct on their part.” (Order, DE 21 at 11.) The
judge considered the totality of the oﬃcers’ testimony, and
their demeanor and appearance. He concluded any discrep-
ancy on this issue was due to mere confusion on the part of
the oﬃcers, and not to fabrication. And he concluded the of-
ficers were credible.
    We see no clear error regarding the judge’s decisions on
any of these issues, nor regarding his decision to find the of-
ficers credible. Given the two bicycle oﬃcers testified they
saw Simon commit a traﬃc infraction, and given the judge be-
lieved them, we see no reason to reverse the decision that
probable cause justified starting the stop.
2. Conducting the stop
    Simon argues even if the oﬃcers did not violate the Con-
stitution by initiating the stop, they violated it by impermissi-
bly prolonging the stop. An oﬃcer who reasonably starts a
traﬃc stop might violate the Constitution if he exceeds the
scope of the stop or unreasonably prolongs it. Lewis, 920 F.3d
at 491. A traﬃc stop “‘can become unlawful if it is prolonged
beyond the time reasonably required to complete th[e] mis-
sion’ of issuing a warning ticket.” Rodriguez v. United States,
135 S. Ct. 1609, 1614–15 (2015) (quoting Illinois v. Caballes, 543
U.S. 405, 407 (2005)).
    A dog sniﬀ of a car’s exterior only for illegal drugs during
a lawful stop for a traﬃc violation does not violate the Fourth
18                                                   No. 18-2442

Amendment, even absent reasonable suspicion of drugs. Ca-
balles, 543 U.S. at 410. But a stop justified only by a traﬃc vio-
lation becomes unconstitutional if the oﬃcers prolong it be-
yond the time reasonably required to complete the stop’s
original mission. Rodriguez, 135 S. Ct. at 1612. “An oﬃcer may
conduct certain unrelated checks—including a dog sniﬀ—
during a lawful traﬃc stop, but he may not do so in a way that
prolongs the stop, absent the reasonable suspicion ordinarily
demanded to justify detaining an individual.” Lewis, 920 F.3d
at 491 (internal quotation marks omitted). As Simon concedes,
“calling a K-9 unit does not unlawfully extend a traﬃc stop as
long as the normal process for pursuing a traﬃc ticket is on-
going.” (Appellant Br. at 36.)
   Without independent reasonable suspicion to justify the
sniﬀ, the critical question is not whether the dog sniﬀed be-
fore or after the oﬃcer issued the warning, “but whether con-
ducting the sniﬀ prolongs—i.e., adds time to—the stop.”
Lewis, 920 F.3d at 491 (internal quotation marks omitted).
With independent reasonable suspicion, however, the oﬃcer
may constitutionally detain the suspect for the sniﬀ even if it
adds time to the total stop. Id.
    Here, the judge continued to credit the oﬃcers’ testimony.
Based on that testimony, the judge concluded the stop was not
improperly prolonged to allow Rex to sniﬀ. The judge noted
the time period from the beginning of the stop to the canine
alert was about 7 minutes, as Simon conceded. The judge de-
termined the oﬃcers acted quickly. Hoecker made the stop,
exited his car, told Simon the reason for the stop, and gathered
his information. The bicyclists arrived at the stop only a cou-
ple minutes after Hoecker pulled Simon over. The bicyclists
“diligently began processing the ticket.” (Order, DE 21 at 15.)
No. 18-2442                                                   19

Crucially, the judge found no indication the oﬃcers engaged
in any activity other than securing the scene and processing
the warning during the time between the bicyclists’ arrival
and Rex’s arrival. Specifically, the oﬃcers surveyed the scene,
Danner spoke with Simon, and Hagemeyer testified she went
to the squad car to begin processing the written warning. The
video indicated that about 2.5 minutes into the stop, Danner
was speaking to Hoecker about the traﬃc violation. About 3
minutes into the stop, Danner left the squad car to speak with
Simon. Danner told Simon the reasons for the stop and gath-
ered information. Hoecker returned to Simon’s car at about
the 5-minute mark to speak with him about the traﬃc infrac-
tion. Less than 7 minutes into the stop, Rex arrived and very
quickly alerted. At that time, the bicycle oﬃcers were still pro-
cessing the ticket.
   In sum, the judge concluded the oﬃcers were processing
the ticket when Rex arrived and alerted, so they had not yet
completed the initial mission of the stop, and the stop was not
improperly prolonged to allow Rex to sniﬀ.
     Simon argues the police report and testimony contain the
“misrepresentation” Hagemeyer was writing the warning
while the oﬃcers waited for Rex because the oﬃcers knew
calling a canine unit does not unlawfully extend a stop so long
as the normal process for pursuing a traﬃc ticket is ongoing.
Simon continues to challenge the credibility of the oﬃcers. He
argues that at no point did any oﬃcer on the scene begin ef-
fectuating the purpose of the stop by dutifully and diligently
filling out a warning or ticket. He claims Danner filled out
both the traﬃc citation and the warning Simon received hours
after the stop. But again we see no reversible error in the
judge’s conclusions on this point.
20                                                   No. 18-2442

    Simon presses that even if the judge’s credibility determi-
nations here are correct, his ruling is still flawed. First, Simon
argues the judge improperly allowed a de minimis delay to be
constitutional, even though any delay to allow a dog to sniﬀ
is unconstitutional absent independent reasonable suspicion.
We disagree with Simon about what the judge did. He specif-
ically found there was no improper delay. (Order, DE 21 at 14
(“the stop was not purposefully prolonged to allow for the ca-
nine unit’s arrival”).) True, the judge added in a footnote that
even if he found the ticket-writing process had not begun
when Rex arrived, still the sequence of events was so short
and condensed that the stop was not prolonged in any “mean-
ingful” way. But we need not review this dictum.
    Second, Simon argues that instead of eﬀectuating the pur-
pose of the traﬃc stop, the oﬃcers decided to run a criminal-
history check. Simon argues this was unrelated to the mission
of the stop and delayed processing the traﬃc violation. Simon
cites no supporting Seventh Circuit case. We said last year that
when police conduct a stop, “they are entitled to demand the
driver’s identification, of course, and it is routine to check the
driver’s record for active warrants, driving history, and crim-
inal history. Those checks are done for important reasons, in-
cluding oﬃcer safety.” Swanigan v. City of Chicago, 881 F.3d
577, 586 (7th Cir. 2018); see also United States v. Sanford, 806
F.3d 954, 956 (7th Cir. 2015) (“The trooper checked the occu-
pants’ criminal histories on the computer in his car—a proce-
dure permissible even without reasonable suspicion … .”).
   We considered all Simon’s arguments, but we see no rea-
son to reverse the judge’s conclusions that the oﬃcers were in
the process of completing the traﬃc warning when Rex
No. 18-2442                                                     21

arrived, and the oﬃcers did not improperly prolong the traﬃc
stop to allow the sniﬀ to occur.
3. Bona Fido?
    Simon argues even if the oﬃcers had probable cause to
pull him over, and even if they did not prolong the traﬃc stop
to wait for Rex, still the judge should have suppressed the gun
because Rex’s alert was false, Rex was improperly trained,
and the alert did not provide probable cause to justify search-
ing Simon’s car.
    Probable cause to conduct a search is not among the high-
est standards. “A police oﬃcer has probable cause to conduct
a search when the facts available to him would warrant a per-
son of reasonable caution in the belief that contraband or evi-
dence of a crime is present.” Florida v. Harris, 133 S. Ct. 1050,
1055 (2013) (internal quotation marks and brackets omitted).
Probable cause is less than preponderance of the evidence. Id.
“All we have required is the kind of fair probability on which
reasonable and prudent people, not legal technicians, act.” Id.
(internal quotation marks and brackets omitted). Probable
cause is a practical, common-sense standard, involving the to-
tality of the circumstances. Id.
   A dog’s alert on a car can give probable cause to search the
entire car. Indeed, a good dog’s alert can provide a rebuttable
presumption of probable cause to search:
       If a bona fide organization has certified a dog
       after testing his reliability in a controlled setting,
       a court can presume (subject to any conflicting
       evidence oﬀered) that the dog’s alert provides
       probable cause to search. The same is true, even
       in the absence of formal certification, if the dog
22                                                            No. 18-2442

         has recently and successfully completed a train-
         ing program that evaluated his proficiency in lo-
         cating drugs.
Id. at 1057. The ultimate question is “whether all the facts sur-
rounding a dog’s alert, viewed through the lens of common
sense, would make a reasonably prudent person think that a
search would reveal contraband or evidence of a crime. A
sniﬀ is up to snuﬀ when it meets that test.” Id. at 1058.
   Simon concedes Rex passed certification tests. But Simon
challenges the alert itself and the adequacy of Rex’s training.
   “First and foremost,” Simon argues Rex did not alert on
Simon’s car. (Appellant Br. at 42.) This perplexes. Simon cites
nothing to support this claim. The record belies it. Given the
context of this claim, Simon seems simply to mean the alert
was false.4 It is true that following the alert the oﬃcers
searched the car and found no evidence of drugs in it. But Si-
mon does not explain why that, in itself, matters here. Proba-
ble cause is not a retrospective, outcome-based standard.

     4 Defense expert Dr. Mary Cablk said in her report she could not de-
termine if Rex alerted or what Rex alerted to. She confirmed this on cross-
examination at the suppression hearing. During direct examination she
watched videos from Hoecker’s and Snyder’s dashcams. She testified she
could not see the alert, could not tell exactly where on the car the dog
alerted, and did not know whether the alert was barking or something
else. But in her testimony she seems to accept Rex alerted. She character-
ized it as a false alert because no drugs were found, and she criticized
Snyder for rewarding Rex for falsely alerting: “In this instance, there’s no
drugs found; so he’s reinforcing the dog for false alerting here.” In any
event, Snyder testified that Rex alerted and that Snyder confirmed the
alert. And the judge throughout his order accepted Rex alerted. He found
the officers’ testimony, in its totality, credible. We see no reason to upend
the determination Rex alerted.
No. 18-2442                                                     23

Bridewell v. Eberle, 730 F.3d 672, 675 (7th Cir. 2013). If an oﬃcer
randomly breaks into a house on only a wild hunch and stum-
bles into a meth lab, the discovery does not provide probable
cause for the search. And if 20 reliable informants tell an of-
ficer a particular house contains a meth lab, so he stands in
the street outside the house and sees through an open win-
dow the apparent apparatus and accoutrements of a meth lab,
so he obtains a warrant to search the house based on probable
cause to think it contains a meth lab, but he finds only an in-
nocent and intricate chemistry set, still probable cause sup-
ported the warrant. So the mere absence of drugs in Simon’s
car does not undermine the probable cause to search it for
drugs, provided there was probable cause in the first place.
   Simon’s other argument is the oﬃcers did not have prob-
able cause to search his vehicle in the first place because Rex
was unreliable. This argument proceeds in two waves.
    The first wave is quickly quelled. Simon argues Rex was
unreliable because he was not trained properly under Illinois
law, which requires police dogs be trained according to cer-
tain guidelines. Simon argues Detective Larner (the Macon
County canine-training director) admitted he did not always
follow these guidelines. But we need not address what Illinois
law requires or whether Rex satisfies it because Illinois law
does not control the Fourth Amendment. See Virginia v. Moore,
553 U.S. 164, 172 (2008) (“[T]he Fourth Amendment’s mean-
ing [does] not change with local law enforcement practices—
even practices set by rule.”); California v. Greenwood, 486 U.S.
35, 43 (1988) (“We have never intimated … that whether or not
a search is reasonable within the meaning of the Fourth
Amendment depends on the law of the particular State in
which the search occurs.”).
24                                                     No. 18-2442

    The second wave holds out longer, but ultimately suc-
cumbs. Simon argues, apart from Illinois law, if a dog is
trained to alert when no evidence of criminal activity exists,
this violates the Fourth Amendment. The problem, as Simon
sees it, is Rex was trained with scented cotton balls to alert to
residual odors. But to search a car, there must be probable
cause to think it presently contains evidence of criminal activ-
ity. So if Rex is trained to alert to mere residue even when no
drugs are present, then his alert is not a reliable indicator
drugs are present, and therefore his alert does not provide
probable cause to justify a search.
    The main problem with this argument is the Supreme
Court already rejected its premise. In Florida v. Harris, a dog
named Aldo alerted on a truck. A subsequent search did not
reveal any of the drugs Aldo was trained to detect, but it did
discover meth ingredients. The defendant moved to suppress
the ingredients on the ground that Aldo’s alert had not given
probable cause to search. The defendant “principally con-
tended” in the trial court that because the oﬃcer did not find
any of the drugs Aldo was trained to detect, Aldo’s alerts
must have been false. Harris, 133 S. Ct. at 1058. But the Su-
preme Court patted Aldo on the head and called him a good
boy: “A well-trained drug-detection dog should alert to [resid-
ual] odors; his response to them might appear a mistake, but
in fact is not.” Id. at 1059; see also Miller v. Vohne Liche Kennels,
Inc., 600 F. App’x 475, 477 (7th Cir. 2015) (Plaintiﬀ’s “only de-
veloped legal theory is untenable. [His] premise—that an alert
by a drug-sniﬃng dog trained to detect residual odors does
not establish probable cause to search—was rejected in Harris
… .”). If a well-trained dog, trained to alert even to residual
odors, alerts, there is generally a fair probability that drugs or
evidence of drugs will be found, absent contradictory factors.
No. 18-2442                                                         25

And that is all the Fourth Amendment requires. If somehow
a dog were trained to alert only to residual odors, then we
might have a problem. But that is not this case.
    Our review of the record and the order denying suppres-
sion satisfies us the judge conducted the proper Harris evalu-
ation and committed no error in concluding Rex’s satisfactory
certification and training provide suﬃcient reason to trust his
alert or in concluding Rex’s training on residual odors is ac-
ceptable. The judge heard testimony from Simon’s expert Dr.
Cablk challenging Rex’s qualifications and the sniﬀ itself, tes-
timony from Oﬃcer Snyder supporting Rex’s qualifications
and the sniﬀ itself, and testimony from Detective Larner sup-
porting Rex’s qualifications and the sniﬀ itself. The judge also
entertained arguments from both sides in the form of the mo-
tion to suppress, supporting memorandum, the government’s
response, and post-hearing briefs filed by both sides. The
judge considered the totality of the circumstances, addressed
Harris’s ultimate question, and found Rex’s sniﬀ up to snuﬀ.
C. Supplementation
    After the judge denied the motion to suppress, Simon
moved to supplement the record and for leave to seek recon-
sideration. He wanted to reopen the evidence to introduce
further, unrelated citations prepared by Danner in August
2016 “which further emphasize the diﬀerences in the oﬃcers’
handwriting … .” (Mot. Supp., DE 23 at 4.) Simon also wanted
to introduce a video he5 took when he returned to the scene
one night. The video shows a vehicle leaving the 1100 block
of College Street and approaching the intersection of College

   5  The motion says Simon created the video. On appeal, Simon asserts
his investigator took the video. This nuance is immaterial here.
26                                                 No. 18-2442

and Green. The judge denied this motion. On appeal, Simon
only presses the video. He does not mention the additional
handwriting exemplars in his opening appellate brief. Simon
acknowledges we review the denial of supplementation for
abuse of discretion.
    The judge did not abuse his discretion. He explained there
was no reason Simon could not have taken a nighttime video
and presented it during the suppression hearing. The judge
discussed the danger of allowing supplementation here and
setting a bad precedent leading to a never-ending cycle of par-
ties waiting for rulings and then coming up with “new” evi-
dence to challenge them. Most importantly, the judge ex-
plained that even with the proposed evidence, his ruling
would not change. The nighttime video would not capture the
actual visual capabilities of the oﬃcers, who credibly testified
about how close Simon was to the intersection when he sig-
naled. The judge reasoned a video of the scene taken months
later, when conditions might diﬀer, would not impact their
credibility. Besides, the judge noted, the probable cause
standard does not need evidence to support a conviction be-
yond a reasonable doubt. He did not abuse his discretion.
D. ACCA
    Simon argues his prior conviction under Illinois law for
attempted armed robbery should not have counted as a pred-
icate oﬀense under the Armed Career Criminal Act. He recog-
nizes our decisions foreclose his argument on this point, but
he wants to preserve it for the Supreme Court.
                       IV. Conclusion
    We considered all Simon’s arguments. Finding no reversi-
ble error, we AFFIRM.
