 United States Court of Appeals
         FOR THE DISTRICT OF COLUMBIA CIRCUIT



Argued March 20, 2015                  Decided June 19, 2015

                         No. 14-7069

    BETTY S. FLYTHE, PERSONALLY, AND AS PERSONAL
 REPRESENTATIVE OF THE ESTATE OF TREMAYNE G. FLYTHE,
                      APPELLANT

                              v.

 DISTRICT OF COLUMBIA, A MUNICIPAL CORPORATION, ET AL.,
                      APPELLEES


        Appeal from the United States District Court
                for the District of Columbia
                    (No. 1:10-cv-02021)


    Gregory L. Lattimer argued the cause for appellant. With
him on the briefs was Ernest W. McIntosh, Jr.

    Carl J. Schifferle, Assistant Attorney General, Office of
the Attorney General for the District of Columbia, argued the
cause for appellees District of Columbia. With him on the brief
were Eugene A. Adams, Interim Attorney General for the
District of Columbia, Todd S. Kim, Solicitor General, and
Loren L. AliKhan, Deputy Solicitor General.

    Robert E. Deso argued the cause and filed the brief for
appellee Travis Eagan.
                               2
    Before: TATEL, KAVANAUGH, and PILLARD, Circuit
Judges.

    Opinion for the Court filed by Circuit Judge TATEL.

     TATEL, Circuit Judge: In this civil action against two
police officers and the District of Columbia, appellant Betty S.
Flythe alleges that in violation of the Fourth Amendment and
D.C. law, each officer assaulted her son and one killed him.
Accepting as true the account of the officer who killed
appellant’s son, the district court found that the officer’s
actions were objectively reasonable and thus granted summary
judgment dismissing all claims against him. The claims against
the District and the other officer went to trial, and the jury
returned a verdict for Ms. Flythe. For the reasons set forth in
this opinion, we affirm the jury’s verdict. But because the
record reveals genuine issues of material fact with respect to
the actions of the officer who fired the fatal shots—thus
making himself the only surviving eyewitness to the actual
killing—we reverse the district court’s grant of summary
judgment in his favor.
                              I.
     On Christmas Day in 2009, an unknown assailant threw a
brick through the window of a liquor store located on Georgia
Avenue in Northwest Washington, setting in motion a chain of
events that led to the death of Tremayne G. Flythe. The store’s
owner, Balbir Singh Hundal, reported the vandalism to the
District of Columbia Metropolitan Police Department and then
called again the next day to report that the same assailant had
tossed an empty bottle at a different window. Early in the
afternoon of December 26, Officers Angel Vazquez and Travis
Eagan arrived at the store and, acting on Hundal’s description
of the alleged vandal as a “black male wearing a black jacket
walking a dog,” they set off in separate cars to canvass the
neighborhood.
                                 3
     Officer Vazquez soon encountered Tremayne Flythe, an
African-American man walking a dog. In his deposition,
Vazquez testified that he parked his cruiser, approached
Flythe, and informed him that the police were doing an
investigation and wanted to ask him a few questions. Angel
Vazquez Dep. 25, Feb. 29, 2012. As directed by Vazquez,
Flythe tied the dog to a fence and began accompanying the
officer to the rear of the cruiser. Id. at 24. Vazquez testified that
as they approached the cruiser, Flythe’s “demeanor started
changing” and he “put[] his right hand on his black jacket,”
prompting the officer to ask “do you have anything on you that
I should know[?]” Id. at 25, 22. According to Vazquez, Flythe,
standing less than a foot away, responded, “yes, I got a knife,”
“pulled out a knife,” and attempted to stab the officer. Id. at 44,
41, 22. Vazquez testified that he then “pushed or kicked”
Flythe, drew his gun, ordered Flythe to drop the knife, and
fired two shots, at which point his gun jammed. Id. at 46, 47.
After clearing the jam, Vazquez fired two additional shots,
both of which missed. Id. at 49–50. Flythe then untied the dog
and ran away. Id. at 50.
     Meanwhile, Officer Eagan, accompanied by store owner
Hundal, was patrolling the same neighborhood and heard the
following over the police radio:
        OFFICER [VAZQUEZ]: Eagan. Four
        hundred block of Kenyon.
        OFFICER [VAZQUEZ]: Hey, (inaudible),
        copy.
        DISPATCHER: 3206 (phonetic).
        OFFICER [VAZQUEZ]: Drop the knife.
        OFFICER [VAZQUEZ]: Shot.
        OFFICER [VAZQUEZ]: Drop the knife.
        (Shot fired)
                           ...
                                 4
        OFFICER [VAZQUEZ]: Tried to stab me,
        ma’am. My gun jammed. Get official on this
        location.
Radio Run Call 3–4, Dec. 26, 2009.
      In his deposition, Eagan testified that shortly after hearing
the radio broadcast and seeing Officer Vazquez “running
in . . . a guard position . . . . [with] his weapon in his hand,” he
encountered Flythe and ordered him to “get on the ground . . .
now[.]” Travis Eagan Dep. 28, 33, Feb. 29, 2012. According to
Eagan, instead of obeying that order, Flythe continued running
“3 to 4 feet” past him before suddenly turning around,
“yell[ing] something loud,” and “ma[king] a motion towards
his waistband,” from which he pulled a knife and “advance[d]
towards” the officer. Id. at 35, 43, 34. Eagan fired his weapon,
striking Flythe in the leg and abdomen. Id. at 43. After
bleeding for more than twenty minutes on the sidewalk, Flythe
was taken to a hospital where he died.
     Tremayne Flythe’s mother, Betty S. Flythe, brought suit in
the United States District Court for the District of Columbia
against Officers Vazquez and Eagan pursuant to 42 U.S.C.
§ 1983, alleging that both officers employed excessive force in
violation of the Fourth Amendment. See Monell v. Department
of Social Services of City of New York, 436 U.S. 658, 700–01
(1978) (section 1983 establishes a private “remedy, to be
broadly construed, against all forms of official violation of
federally protected rights”). Ms. Flythe also brought
common-law assault and battery, wrongful death, and survival
claims against both officers and the District of Columbia as
their employer. Finally, alleging that the District breached its
duty to properly train and supervise the two officers, Ms.
Flythe brought a common-law negligent supervision claim
against the city.
                                5
     All defendants—the two officers and the District—moved
for summary judgment. Against the excessive force claim, the
officers asserted qualified immunity, which protects law
enforcement officials “from suit under 42 U.S.C. § 1983 unless
they have violated a statutory or constitutional right that was
clearly established at the time of the challenged conduct.” City
& County of San Francisco v. Sheehan, 135 S. Ct. 1765, 1774
(2015) (internal quotation marks omitted). With respect to
Officer Vazquez, the district court ultimately found “a genuine
issue of material fact as to whether Mr. Flythe did, in fact, pose
a threat of serious physical harm” justifying Officer Vazquez’s
use of force and thus denied summary judgment. Flythe v.
District of Columbia, 4 F. Supp. 3d 216, 221 (D.D.C. 2014).
This issue of material fact, the district court ruled, also
precluded summary judgment for Officer Vazquez on the
assault and battery claim “as a reasonable fact-finder could
conclude based on the evidence proffered by the plaintiff that
Mr. Flythe carried no weapon and did not otherwise threaten
Officer Vazquez during their encounter.” Flythe v. District of
Columbia, 994 F. Supp. 2d 50, 74 (D.D.C. 2013).
     The district court reached a different conclusion as to
Officer Eagan. Given the radio transmission reporting that
Flythe had tried to stab Vazquez, and accepting as “fact[]” that
“Flythe did not stop [as Eagan ordered], but instead turned
around, yelled, [and] reached toward the waistband of his pants
which contained a knife,” the court found that Eagan “acted as
a reasonable officer would have confronted with the same
circumstances” and was thus entitled to qualified immunity. Id.
at 66, 67. Based on the “undisputed” evidence “that Mr. Flythe
had a knife that put Officer Eagan and third-party members of
the public in imminent peril of death or serious bodily injury,”
the district court further concluded that Officer Eagan “was
privileged to act, and therefore cannot be liable for battery.” Id.
at 74. The district court therefore granted summary judgment
dismissing all claims against Eagan.
                                6
      Regarding the District’s alleged negligent supervision, the
district court held that Ms. Flythe had failed to “put forth any
evidence that the District knew or should have known that
Officer Vazquez was particularly dangerous or incompetent.”
Id. at 72. With respect to Officer Eagan, the district court found
it irrelevant that supervisors had questioned his fitness for duty
two months prior to the shooting and had ultimately fired him
after he tested positive for methamphetamines just four days
after killing Flythe. “[T]he District’s failure to properly
supervise Officer Eagan,” the court reasoned, “was not a
substantial factor in bringing about Mr. Flythe’s death because
any officer in Officer Eagan’s position would likely have shot
Mr. Flythe in the circumstances.” Flythe v. District of
Columbia, 19 F. Supp. 3d 311, 318 (D.D.C. 2014). The court
therefore granted summary judgment to the District on the
negligent supervision claim.
     The district court denied summary judgment, however, on
the question whether the District was vicariously liable for any
assault and battery committed by its officers. “[A]ssess[ing]
both officers’ encounter with Mr. Flythe as a . . . single
transaction,” the court concluded that “Officer Eagan acted in
reliance on representations by Officer Vazquez in his
altercation with Mr. Flythe” and thus “a genuine dispute of
material fact [remained] as to whether Mr. Flythe presented a
danger throughout the encounter with both officers[.]” Flythe,
994 F. Supp. 2d at 75, 76.
     To sum up, then, only the section 1983 and assault and
battery claims against Officer Vazquez, as well as the vicarious
assault and battery claim against the District, survived
summary judgment and proceeded to trial. In keeping with its
dismissal of Ms. Flythe’s negligent supervision claim, the
district court excluded expert testimony regarding the
District’s supervision of Officer Eagan. Flythe v. District of
Columbia, 4 F. Supp. 3d 222, 230 (D.D.C. 2014). And finding
                                7
that “evidence regarding Officer Eagan’s subjective judgment
is not probative on the issue of the objective reasonableness of
his actions,” the district court refused to permit expert
testimony or cross-examination regarding Officer Eagan’s
methamphetamine use or fitness for duty. Id. at 227.
     Following a six-day trial, the jury found Officer Vazquez
liable for assault and the District vicariously liable for assault
and battery committed by both officers. The jury found no
liability, however, on the battery and section 1983 claims
against Officer Vazquez. Against the District only, the jury
awarded Ms. Flythe $187,300 in compensatory damages. But
because Tremayne Flythe’s final medical bills were paid by
Medicaid, the city asked the district court to reduce the
damages award by the cost of those bills in order to prevent his
mother from “receiv[ing] a windfall.” Defs.’ Reply to Pl.’s
Opp’n to Set-Off Mot. 2, Apr. 24, 2014. Granting the motion,
the district court reduced the jury award to $119,253.24.
     Ms. Flythe now appeals, arguing that the district court
erred in granting summary judgment to Eagan on the section
1983 and assault and battery claims, as well as to the District
on the negligent supervision claim. Ms. Flythe also challenges
the district court’s exclusion of expert testimony and denial of
cross-examination regarding Officer Eagan’s fitness for duty
and drug use, as well as the court’s jury instructions and
reduction of the damages award.
                              II.
     We begin with Ms. Flythe’s claim that the district court
erred in holding Officer Eagan immune from liability for his
use of deadly force. In order to protect law enforcement
officers from the “sometimes hazy border between excessive
and acceptable force,” Saucier v. Katz, 533 U.S. 194, 206
(2001) (internal quotations and citation omitted), qualified
immunity shields them “from damages suits for actions taken
                                8
while carrying out their official duties,” Fenwick v. Pudimott,
778 F.3d 133, 137 (D.C. Cir. 2015). This shield, however, is
not impenetrable, for officers enjoy no protection for violations
of clearly established constitutional rights. See Plumhoff v.
Rickard, 134 S. Ct. 2012, 2023 (2014) (“An official sued under
§ 1983 is entitled to qualified immunity unless it is shown that
the official violated a statutory or constitutional right that was
clearly established at the time of the challenged conduct.”).
     Here, Ms. Flythe alleges that Officer Eagan killed her son
in violation of the Fourth Amendment. Apprehension of a
suspect through deadly force, i.e., killing him, qualifies as a
Fourth Amendment seizure, Tennessee v. Garner, 471 U.S. 1,
7 (1985), and is therefore unlawful unless “objectively
reasonable in light of the facts and circumstances confronting
[the officer],” Graham v. Connor, 490 U.S. 386, 397 (1989)
(internal quotation marks omitted). Ms. Flythe also contends
that Eagan’s actions amounted to assault and battery in
violation of D.C. law, which, like federal law, immunizes
officers to the extent their actions are reasonable. See
Etheredge v. District of Columbia, 635 A.2d 908, 916 (D.C.
1993) (“A police officer has a qualified privilege to use
reasonable force to effect an arrest, provided that the means
employed are not in excess of those which the actor reasonably
believes to be necessary.”) (internal quotation marks omitted).
     Although deciding deadly force cases typically requires
that we “slosh our way through the factbound morass of
reasonableness,” Scott v. Harris, 550 U.S. 372, 383 (2007)
(internal quotation marks omitted), here we need consider only
one question: What happened when Tremayne Flythe turned to
face Officer Eagan? If, as Officer Eagan claims, Flythe
attacked him with a knife, then Eagan reasonably responded to
an imminent threat. See id. at 384 (officers may use deadly
force where a suspect “pose[s] an actual and imminent threat to
the lives of . . . the officers involved”). But if, as Ms. Flythe
                                9
contends, Tremayne obeyed Officer Eagan’s command to
“stop” and turned around to surrender, then Eagan’s actions
were patently unreasonable. See Garner, 471 U.S. at 11 (“A
police officer may not seize an unarmed, nondangerous suspect
by shooting him dead.”). On this question, we may affirm the
district court’s grant of summary judgment only if, after
viewing the facts in the light most favorable to Ms. Flythe and
drawing every reasonable inference in her favor, we can say
that no rational trier of fact could disbelieve Officer Eagan’s
account. See Scott, 550 U.S. at 378 (“[C]ourts are required to
view the facts and draw reasonable inferences in the light most
favorable to the party opposing the summary judgment
motion.”) (internal quotation marks and alterations omitted).
                              A.
     An African proverb teaches that only when lions have
historians will hunters cease being heroes. Put another way,
history is usually written by those who survive to tell the tale,
and in this case the only survivor is Officer Eagan. Tremayne
Flythe is dead and, although several witnesses observed the
two men face each other, none can testify as to exactly what
happened between them. Under these circumstances, where
“the witness most likely to contradict [the officer’s] story—the
person [he] shot dead—is unable to testify,” courts, as the
Ninth Circuit has explained, “may not simply accept what may
be a self-serving account by the police officer.” Scott v.
Henrich, 39 F.3d 912, 915 (9th Cir. 1994). Instead, courts must
“carefully examine all the evidence in the record . . . to
determine whether the officer’s story is internally consistent
and consistent with other known facts.” Id. Courts “must also
look at the circumstantial evidence that, if believed, would tend
to discredit the police officer’s story, and consider whether this
evidence could convince a rational factfinder that the officer
acted unreasonably.” Id.
                               10
      Every circuit to have confronted this situation—where the
police officer killed the only other witness to the
incident—follows this approach. For example, the Seventh
Circuit has explained that “[t]he award of summary judgment
to the defense in deadly force cases may be made only with
particular care where the officer defendant is the only witness
left alive to testify.” Plakas v. Drinski, 19 F.3d 1143, 1147 (7th
Cir. 1994). Accordingly, “a court must undertake a fairly
critical assessment of the forensic evidence . . . to decide
whether the officer’s testimony could reasonably be rejected at
a trial.” Id.; see also Jefferson v. Lewis, 594 F.3d 454, 462 (6th
Cir. 2010); Ingle ex rel. Estate of Ingle v. Yelton, 439 F.3d 191,
195 (4th Cir. 2006); O’Bert ex rel. Estate of O’Bert v. Vargo,
331 F.3d 29, 37 (2d Cir. 2003); Abraham v. Raso, 183 F.3d
279, 294 (3d Cir. 1999); Ludwig v. Anderson, 54 F.3d 465, 470
n.3 (8th Cir. 1995); Hegarty v. Somerset County, 53 F.3d 1367,
1376 n.6 (1st Cir. 1995).
                              B.
    In this case, record evidence casting doubt on Officer
Eagan’s testimony abounds. Indeed, in several significant
respects Eagan’s testimony conflicts with that of every other
witness, as well as the physical evidence.
    First, in his deposition, Eagan described his initial
encounter with Flythe. “As I exited my vehicle,” he testified,
“Flythe had gotten there and just as we met, he then proceeded
to pass me just a little bit.” Eagan Dep. 32, 33. According to
Eagan, it was immediately after this that Flythe turned around
and attacked him with a knife. Id. at 34.
    Three individuals who witnessed the first moments of the
encounter, however, testified that the incident actually began
with Eagan chasing Flythe while firing his weapon. A nearby
neighbor, Ursula Edmonds, told police investigators that “as
soon as [Eagan’s] car pulled up, the police
                               11
officer . . . . [i]mmediately jumped out of the car, . . . started
running” and “shooting at the young man.” Ursula Edmonds
Interview 8, 9, Dec. 26, 2009. Another neighbor, Ivan Cloyd,
stated that he saw Flythe “running when the officer was
shooting at him.” Ivan Cloyd Interview 4, Dec. 26, 2009. And
store owner Hundal, who was riding in the cruiser with Eagan,
testified that the officer exited the car and chased Flythe while
shooting and “say[ing,] stop, stop.” Balbir Singh Hundal Dep.
77, 66, Oct. 5, 2012.
     The testimony of these three witnesses finds support in the
physical evidence. Although only two bullets struck Flythe,
investigators recovered three additional bullets that had been
fired from Eagan’s weapon on the street where Flythe was
shot. This is consistent with the testimony of Edmonds, Cloyd,
and Hundal, all of whom said that Eagan repeatedly fired at
Flythe and missed.
     Second, Eagan testified that Flythe, after running “3 to 4
feet” past him, suddenly “jumped through the air and changed
his momentum by doing a hop . . . and started coming towards
me,” causing the officer to begin “running backwards or
walking backwards, retreating.” Eagan Dep. 35, 34. Two
witnesses told a different story. Even with a clear view of
Flythe’s head and shoulders, store owner Hundal said nothing
at all about a mid-air hop or a backwards retreat. Rather, he
testified that after Eagan ordered Flythe to “stop,” Flythe
turned around and “went face to face with Officer Eagan.”
Hundal Dep. 90, 91. According to Hundal, he heard the fatal
shots immediately “[a]t that time.” Id. at 90. The other witness,
Officer Vazquez, said nothing at all about Flythe changing
direction. Instead, Vazquez testified that Eagan “exited his car”
as “Mr. Flythe was running towards Mr. Eagan.” Vazquez
Dep. 60. Vazquez “saw [Flythe] motion towards Officer
Eagan” and then “heard the two shots.” Id. at 62. Asked
                              12
whether prior to those shots, he “ever [saw] Flythe stop
running,” Officer Vazquez answered “[n]o, no.” Id. at 63.
     Third, Eagan’s testimony about the knife conflicts in
critical respects with the testimony of other witnesses.
According to Eagan, Flythe raised the knife “with the blade
pointing down and the handle up.” Eagan Dep. 42; see also
Eagan Trial Test. 122 (“[Flythe] raised the knife above his
head”); id. at 114 (“[Flythe] raised it above his head and
advanced towards me”). Yet Hundal, who had a clear view of
both men’s heads and shoulders and who was questioned
intensely about what he saw, said nothing at all about Flythe
raising a knife. Officer Vazquez also had a clear view—he saw
a “motion towards Officer Eagan,” Vazquez Dep. 62—but
likewise said nothing about Flythe raising a knife.
Neighborhood resident Demetrius Moore, who observed the
scene immediately after the shooting, testified that despite
“looking[] and trying to see all [she] could see,” she saw no
knife near Flythe as he lay wounded on the ground. Demetrius
Moore Dep. 16, Apr. 2, 2012. True, the police ultimately
recovered a knife “six inches or a foot away from [Flythe’s]
foot,” Warren E. Jones Dep. 27, Mar. 23, 2012, but Flythe’s
fingerprints were never found on the knife, Raymond E. Bond
Dep. 48, Mar. 21, 2012. And for unknown reasons, the police
chose not to test the knife for Flythe’s DNA despite having
swabbed it for precisely that purpose. Id. at 48–49.
     Moreover, and further undermining Eagan’s claim that
Flythe had a knife, all five witnesses to Officer Vazquez’s
confrontation with Flythe testified that Flythe had no knife at
that time. Despite Officer Vazquez’s command, heard on the
radio transmission, to “drop the knife,” all five witnesses
unequivocally stated that Flythe’s hands were empty. In fact,
three of the witnesses saw Flythe with his hands raised, palms
forward. Moreover, a passing driver, the witness most
supportive of Officer Vazquez’s account, testified that
                              13
although Flythe was “aggressive” and “rush[ed] towards
[Vazquez],” she “specifically saw [Flythe’s] hands as he
advanced at the police officer and did not see a weapon in his
hands.” Sabrina Shapiro Dep. 33, 7, 32, Apr. 2, 2012.
     Finally, the record contains evidence that could lead a
reasonable juror to question Officer Eagan’s personal
credibility and his ability to observe, perceive, and recall the
shooting. Two months prior to the shooting, Eagan’s
supervisor, Lieutenant Madeline Timberlake, “noticed a
change in his work performance as well as his demeanor.”
Madeline Timberlake Mem., Oct. 15, 2009. Eagan told
Lieutenant Timberlake that “he had a sleeping disorder” for
which his doctor had prescribed “strong[] medication.” Id.
Believing “that Officer Eagan should be evaluated mentally as
well as physically to determine if he [was] capable of
performing his duties,” Lieutenant Timberlake revoked his
police powers and relieved him of his firearm pending a
fitness-for-duty examination. Id.; see also Notice of Duty &
Pay Status 1, Oct. 15, 2009. But just two weeks later, and
without having undergone any examination, Eagan’s police
powers were inexplicably restored and his gun returned. Notice
of Duty & Pay Status 1. Moreover, four days after killing
Tremayne        Flythe,    Eagan      tested    positive     for
methamphetamines. Although claiming medication prescribed
by a doctor caused the positive test, Eagan “could not provide
any specific information on the dose, when he took it, and he
could not provide any evidence of it being given to him (no
prescription, no doctor record, no verbal confirmation from a
doctor, etc.).” Myron Weiner Expert Rep. 2, Oct. 19, 2012. The
District argues that the positive test is irrelevant because it
occurred four days after the killing, but in his deposition,
Eagan agreed that whatever substance he “took before [the]
drug test on December 30, 2009 is the same thing [he] took
before [he] shot Tremayne Flythe on December 26, 2009.”
                                14
Eagan Dep. 65. Indeed, the police department fired him after
concluding that he lied about using illegal methamphetamines.
     The district court dismissed all of this evidence, finding
that “whether or not Mr. Flythe actually brandished a knife
against Officer Eagan is largely irrelevant” because given the
radio transmission indicating that Flythe attempted to stab
Officer Vazquez, “it was objectively reasonable for Officer
Eagan to believe that Mr. Flythe had a knife and was
dangerous—whether or not he actually ever saw the knife
himself (or whether or not the knife found near Mr. Flythe’s
body actually belonged to him).” Flythe, 994 F. Supp. 2d at 68.
We disagree. That an individual at one point posed a threat
does not grant officers an irrevocable license to kill.
Justification for deadly force exists only for the life of the
threat. As the Supreme Court has explained, “police officers
are justified in firing at a suspect in order to end a severe threat
to public safety . . . until the threat has ended.” Plumhoff, 134 S.
Ct. at 2022 (emphasis added). Here, the threat to Vazquez had
ended by the time Eagan confronted Flythe, and Eagan never
claimed that he viewed Flythe as an immediate threat. Quite to
the contrary, Eagan testified that his first instinct upon
encountering Flythe was “to holster [his] weapon” and
“engage[] in a foot pursuit[.]” Eagan Dep. 33.
     Accordingly, whether Eagan acted reasonably does turn
on whether, as he alleges, Flythe attacked him with a knife.
And given all of the evidence discussed above—the
inconsistencies between Eagan’s testimony and the testimony
of other witnesses, the physical evidence, and the evidence
raising questions about Eagan’s personal credibility—and
drawing all inferences in Ms. Flythe’s favor, we believe that a
reasonable jury could conclude that Tremayne Flythe never
threatened Officer Eagan with a knife. True, a jury could also
conclude that he did, but “[c]redibility determinations, the
weighing of the evidence, and the drawing of legitimate
                                 15
inferences from the facts are jury functions, not those of a
judge . . . on a motion for summary judgment.” Anderson v.
Liberty Lobby, Inc., 477 U.S. 242, 255 (1986). We shall
therefore reverse the district court’s grant of summary
judgment to Officer Eagan.
                               III.
    We can easily resolve Ms. Flythe’s remaining arguments.
Although the jury returned a verdict in her favor in the trial
against Officer Vazquez and the city, and awarded her
compensatory damages, Ms. Flythe seeks a new trial on two
grounds.
     First, Ms. Flythe contends that the district court
erroneously excluded expert testimony and precluded
cross-examination regarding Officer Eagan’s credibility. As
indicated above, we agree that the district court erred when it
found Eagan’s sleep disorder and drug use insufficient to place
his “ability to perceive or recall facts . . . legitimately at issue”
and irrelevant to the “question . . . whether both officers are
lying.” Flythe, 4 F. Supp. 3d at 227, 229. In order to set aside
the jury’s verdict on this ground, however, Ms. Flythe “must
explain why the erroneous ruling caused harm.” Shinseki v.
Sanders, 556 U.S. 396, 410 (2009). And having obtained a
favorable verdict despite the district court’s errors, Ms. Flythe
suffered no harm with respect to the jury’s liability finding, and
she never argued that the error affected the jury’s calculation of
compensatory damages.
     Second, Ms. Flythe challenges the district court’s jury
instructions on the grounds that they were confusing and
misleading. But Ms. Flythe has forfeited this claim because she
has never—neither here nor in the district court—identified
any specific legal error in the instructions. See Palmer v.
Hoffman, 318 U.S. 109, 119 (1943) (“In fairness to the trial
court and to the parties, objections to a charge must be
                                16
sufficiently specific to bring into focus the precise nature of the
alleged error.”).
      Ms. Flythe also argues that the district court should never
even have instructed the jury on whether Officer Vazquez’s
encounter with Tremayne Flythe constituted a Fourth
Amendment seizure. Such “a seizure occurs when physical
force is used to restrain movement or when a person submits to
an officer’s show of authority,” United States v. Brodie, 742
F.3d 1058, 1061 (D.C. Cir. 2014), and Ms. Flythe argues that
“it is undisputed” that this occurred in this case, Pl.’s Br. 48.
But the district court disagreed, finding that “there is a genuine
issue of fact as to whether Mr. Flythe momentarily submitted
to Officer Vazquez’s show of authority,” Flythe, 4 F. Supp. 3d
at 220, a ruling Ms. Flythe failed to appeal. We therefore find
no error in the district court’s submission of this factual
question and concomitant instructions to the jury.
     In addition to challenging the jury’s verdict, Ms. Flythe
argues that the district court erroneously granted summary
judgment to the District on her negligent supervision claim.
But she has failed to show how compensatory damages—the
only type of damages recoverable against the District, see
Smith v. District of Columbia, 336 A.2d 831, 832 (D.C. 1975)
(“[A]s a general rule there can be no recovery of punitive
damages against a municipality absent a statute expressly
authorizing it. There is no such statute in [the District of
Columbia]”)—would differ had this theory of liability been
submitted to the jury. Unlike punitive damages, which are
intended to “punish the wrongdoer,” Brown v. Coates, 253
F.2d 36, 40 (D.C. Cir. 1958), compensatory damages are
assessed only to “make plaintiffs whole for the harms that they
have suffered as a result of defendants’ actions,” Hendry v.
Pelland, 73 F.3d 397, 402 (D.C. Cir. 1996). Here, the jury
valued Tremayne Flythe’s harm at $187,300, and “in the
absence of punitive damages a plaintiff can recover no more
                                17
than the loss actually suffered,” Medina v. District of
Columbia, 643 F.3d 323, 326 (D.C. Cir. 2011) (internal
quotation marks and citation omitted). In other words, Flythe’s
harm—his pain and suffering, mental anguish, and emotional
distress—cannot be increased just because there is more than
one theory under which the District is liable for his death.
Thus, even if the district court should have permitted
presentation of the negligent supervision claim to the jury,
along with the vicarious assault and battery claim, its failure to
do so was harmless because Ms. Flythe “cannot recover the
same [compensatory] damages twice, even though the
recovery is based on two different theories.” Id. And although
Ms. Flythe now argues that the jury’s compensatory damages
award is inadequate and nonsensical, she forfeited that claim
by failing to raise it in the district court. Ryen v. Owens, 446
F.2d 1333, 1334 (D.C. Cir. 1971) (“[A] motion for a new trial
must be made to the trial court if a party desires to attack on
appeal a judgment in a jury case on the ground that the
damages are inadequate.”).
     Finally, Ms. Flythe challenges the district court’s
deduction of Tremayne Flythe’s medical costs from the jury’s
damages award. But D.C. law provides that “whenever the
District is a defendant in a proceeding brought by a
beneficiary, it shall have a right to set off from a judgment
against it any damages that represent compensation for the care
and treatment it has undertaken to provide or pay for as
health-care assistance.” D.C. Code § 4-603(a). Once the jury
determines “the amount of full, just compensation,” the trial
court must “thereafter adjust the verdict by the amount of any
applicable setoff.” Reid v. District of Columbia, 391 A.2d 776,
778 (D.C. 1978). In this case, the district court admitted the bill
for Tremayne Flythe’s final medical expenses into evidence,
and it is undisputed that the city paid that bill through
Medicaid. It was thus entitled to a setoff.
                              18
                             IV.
    For the foregoing reasons, we reverse the district court’s
grant of summary judgment on the section 1983 and assault
and battery claims against Travis Eagan and remand for further
proceedings consistent with this opinion. In all other respects,
we affirm.
                                                    So ordered.
