PUBLISH

UNITED STATES COURT OF APPEALS

FOR THE TENTH CIRCUIT

_________________________________

UNITED STATES OF AMERICA, 

 Plaintiff - Appellee,

v.

BRIAN TONY,

 Defendant - Appellant.

No. 18-2182

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APPEAL FROM THE UNITED STATES DISTRICT COURT 

FOR THE DISTRICT OF NEW MEXICO 

(D.C. No. 1:16-CR-02904-MV-1)

_________________________________

Josh Lee, Assistant Federal Public Defender (Virginia L. Grady, Federal 

Public Defender, with him on the briefs), Denver, Colorado, for DefendantAppellant.

Joseph M. Spindle, Assistant United States Attorney (John C. Anderson, 

United States Attorney, and Dustin C. Segovia, Assistant United States 

Attorney, Las Cruces, New Mexico, on the brief), Albuquerque, New 

Mexico, for Plaintiff-Appellee.

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Before BRISCOE, KELLY, and BACHARACH, Circuit Judges.

_________________________________

BACHARACH, Circuit Judge.

_________________________________

This appeal is brought by Mr. Brian Tony, who was convicted of 

first-degree murder for fatally stabbing Mr. Pat Garcia during a fight. 

FILED

United States Court of Appeals

Tenth Circuit

January 27, 2020

Christopher M. Wolpert

Clerk of Court
2

Before trial, Mr. Tony sought to introduce evidence that Mr. Garcia had 

used methamphetamine before the fight. The district court excluded the 

evidence, and Mr. Tony argues that the evidence should have been allowed

into evidence. In our view, the district court excluded the evidence for a 

reason unsupported by the record. We thus reverse and remand for a new 

trial. 1

I. The district court excluded the methamphetamine evidence on the 

ground that Mr. Tony failed to identify a proper purpose.

Mr. Tony admitted that he had killed Mr. Garcia. But Mr. Tony 

denied premeditation and asserted self-defense, arguing that he was 

protecting himself from Mr. Garcia. Given the assertion of self-defense, 

the district court allowed Mr. Tony to present evidence of Mr. Garcia’s 

erratic and violent behavior. But Mr. Tony wanted to go further: he wanted 

to elicit evidence that Mr. Garcia had reacted erratically and violently

because he was under the influence of methamphetamine. The district court 

excluded this evidence under Federal Rule of Evidence 404(b) on the 

ground that Mr. Tony had failed to identify a proper purpose. 

 1 Mr. Tony also argues that the judge erred by informing the venire

(upon inquiry) that the case was not a death-penalty case. Given our 

reversal based on exclusion of the methamphetamine evidence, we need not 

reach Mr. Tony’s argument involving the statement to the venire. 
3

II. Under the abuse-of-discretion standard, reversal is necessary 

when the district court relies on a clearly erroneous 

understanding of the record.

We review the exclusion of evidence under the abuse-of-discretion

standard. United States v. Ramone, 218 F.3d 1229, 1234 (10th Cir. 2000).

A court abuses its discretion when relying on a clearly erroneous 

understanding of the record. See Cooter & Gell v. Hartmarx Corp., 496 

U.S. 384, 405 (1990) (“A district court would necessarily abuse its 

discretion if it based its ruling on . . . a clearly erroneous assessment of the 

evidence.”).

III. The district court abused its discretion by excluding the 

methamphetamine evidence based on Mr. Tony’s alleged failure

to identify a proper purpose.

Rule 404(b) prohibits using evidence of other acts “to prove a 

person’s character in order to show that on a particular occasion the person 

acted in accordance with the character.” Fed. R. Evid. 404(b)(1). But the

rule provides an exception: evidence of other acts may be admitted for 

non-propensity purposes. Fed. R. Evid. 404(b)(2). 

To invoke this exception, the proponent of the evidence bears a 

threshold obligation to tell the court what the purpose is. United States v. 

Birch, 39 F.3d 1089, 1093 (10th Cir. 1994). But even if the proponent 

identifies a permissible purpose, the evidence may still be inadmissible on 

grounds of relevance, unfair prejudice, or necessity of expert testimony. 

See Fed. R. Evid. 104(b), 402, 403. 
4

The district court excluded the methamphetamine evidence at the 

threshold stage, ruling that Mr. Tony had identified no proper purpose for 

the evidence. 2 But this ruling is clearly erroneous based on the record. In 

responding to the motion in limine, Mr. Tony stated in writing and in court 

that he was offering the methamphetamine evidence to show why Mr. 

Garcia was acting erratically and violently. This purpose would have been 

permissible under Rule 404(b).

In responding to the government’s motion in limine to exclude the 

methamphetamine evidence, Mr. Tony argued:

When viewed through a neutral lens, the very evidence 

produced by the Government suggests the victim was the first 

aggressor in this case. The evidence will support that the alleged 

victim was intoxicated on methamphetamine and from the 

electrolytes in his system, that he had been under the influence 

of methamphetamine at the time of the incident. The Defense 

will introduce evidence regarding the effects of 

methamphetamine on human behavior. Such evidence will not be 

offered for the purpose of proving the alleged victim acted in 

conformity with his violent character; rather, pursuant to Rule 

404(b), it will be offered for another purpose. There is no 

question that the alleged victim was not only habitually armed 

 2 Mr. Tony also argues that the evidence should have been allowed as 

intrinsic evidence. The government argues that Mr. Tony waived this 

argument in district court by relying on Rule 404(b). We need not decide 

whether Mr. Tony waived the argument. Even if he hadn’t, he would have 

forfeited the argument by failing to raise it in district court. United States 

v. Tapaha, 891 F.3d 900, 909 n.6 (10th Cir. 2018). When an argument is 

forfeited, we ordinarily apply plain-error review. United States v. Battles, 

745 F.3d 436, 445 n.9 (10th Cir. 2014). But Mr. Tony does not argue plain 

error in this appeal, so we would decline to consider this issue even if it 

had not otherwise been waived. United States v. Lamirand, 669 F.3d 1091, 

1098–100 n.7 (10th Cir. 2012). 
5

with a large sheath knife, he used that very knife to inflict a 

potentially mortal wound on the Defendant.

R. vol. I, at 49–50. The government apparently understood this explanation 

of the purpose, responding that “the probative value of [Mr. Garcia’s] drug 

use to support his ‘violent behavior’ [was] tenuous at best and highly 

prejudicial.” Id. at 54.

The district court then considered the issue at a pretrial hearing. 

Moments before discussing the motion in limine, the parties addressed the 

need for a jury instruction on self-defense. Urging an instruction on selfdefense, Mr. Tony argued that the jury could reasonably find self-defense 

based on his efforts to ward off Mr. Garcia’s methamphetamine-fueled 

attack:

Your Honor, the – I’d ask the Court to take judicial notice 

that meth is one of those drugs that makes people do irrational 

and sometimes highly violent things. Your Honor, we – there 

will be testimony that the deceased kept – kept fighting with Mr. 

Tony continually, and Mr. – the deceased was still alive when 

Mr. Tony finally was able to haul himself out of the arroyo after 

suffering some rather horrible wounds himself. Your Honor, the 

fact that the deceased did have numerous wounds is simply an 

indication how violent the fight itself was, how life-threatening 

it was to Mr. Tony, also.

Suppl. R. vol. IV, at 15. The government again understood the purpose, 

acknowledging that Mr. Tony was offering the methamphetamine evidence 

to argue that the victim had acted violently: “What Defense is basically 

trying to say is somebody who uses methamphetamine is inherently 

violent.” Id. at 21.
6

The court didn’t immediately decide whether it would instruct on 

self-defense. The court instead shifted the discussion to the admissibility 

of the methamphetamine evidence. With this shift in the discussion, Mr. 

Tony did not repeat the purpose offered in his written objection. There was 

no need because Mr. Tony had identified this purpose only moments earlier

when arguing that the jury could reasonably find self-defense.

Given the clarity of Mr. Tony’s explanation and the government’s 

understanding, the district court relied on a clearly erroneous view of the 

record when ruling that Mr. Tony had failed to identify a permissible 

purpose for the methamphetamine evidence.

IV. We cannot affirm on alternative grounds.

This is not to say that the methamphetamine evidence was 

admissible, for not all evidence of a witness’s prior drug use is admissible. 

Though Mr. Tony identified a proper purpose for the methamphetamine 

evidence, it might have been excludable as irrelevant or lacking a 

foundation in expert testimony. 3 Fed. R. Evid. 104(b), 402. 

If the evidence were inadmissible on any of these grounds, we might 

be able to affirm on alternative grounds. But the district court had

 3 The evidence might have also been excluded under Rule 403, which 

requires balancing the evidence’s probative value against dangers such as 

the risk of unfair prejudice. Fed. R. Evid. 403. But when a district court 

excludes evidence for reasons other than Rule 403, we may not conduct the 

balancing test for the first time on appeal. Sprint/United States Mgmt. Co. 

v. Mendelsohn, 552 U.S. 379, 386–87 (2008).
7

discretion to decide whether the evidence was relevant or required expert 

testimony, and the court never exercised that discretion. So we can affirm 

on alternative grounds only if it would have been an abuse of discretion to 

permit introduction of the evidence. See Ashby v. McKenna, 331 F.3d 1148, 

1151 (10th Cir. 2003) (“[W]ith respect to a matter committed to the district 

court’s discretion, we cannot invoke an alternative basis to affirm unless 

we can say as a matter of law that ‘it would have been an abuse of 

discretion for the trial court to rule otherwise.’” (quoting Orner v. Shalala, 

30 F.3d 1307, 1310 (10th Cir. 1994))). 

Under this standard, we consider whether the district court had 

discretion to consider the methamphetamine evidence relevant without a 

foundation of expert testimony. The government argues that expert witness 

testimony was necessary to show that

• Mr. Garcia had been under the influence of methamphetamine 

during the fight and

• methamphetamine had caused his aggressive behavior.

The district court had discretion to credit these arguments, but the court 

also had discretion to reject them.

The necessity of expert testimony involves the principle of 

conditional relevance. Under this principle, a district court may exclude 

evidence if the jury could not reasonably find the existence of a 

preliminary fact essential to make the evidence relevant. United States v. 
8

Platero, 72 F.3d 806, 814 (10th Cir. 1995). Though Mr. Tony had agreed 

not to present expert testimony, he might not have needed an expert 

witness for a reasonable jury to find that Mr. Garcia had been under the 

influence of methamphetamine. Methamphetamine had been found on Mr. 

Garcia’s body and in his bloodstream. Together, this evidence supported an 

inference that Mr. Garcia was on methamphetamine, and lay witnesses may 

have been able to testify that he was high. So Mr. Tony might not have 

needed expert testimony to show that methamphetamine causes erratic, 

violent behavior. See United States v. Foote, 898 F.2d 659, 665 (8th Cir. 

1990) (“[T]he effects of cocaine addiction on an individual’s mental 

prowess were within the jury’s common understanding.”).

The district court ultimately had discretion to either (1) decline to 

exclude the evidence before hearing whether a lay witness would have 

testified that Mr. Garcia was under the influence of methamphetamine or 

(2) allow a lay witness to testify about the effect of methamphetamine on

Mr. Garcia’s behavior. Given this discretion, we cannot affirm on the 

government’s alternative grounds. We thus conclude that the district court 

abused its discretion in excluding the evidence based on a clearly

erroneous understanding that Mr. Tony had failed to identify a permissible

purpose.
9

V. The district court’s error was not harmless.

Like other errors, abuses of discretion may be harmless. See United 

States v. Vaughn, 370 F.3d 1049, 1051 (10th Cir. 2004) (“[W]e review [the 

defendant’s] evidentiary claims for an abuse of discretion, and if we find 

an abuse of discretion, we must determine whether the error was 

harmless.”). But premature exclusion of the methamphetamine evidence 

was not harmless.

The government bears the burden of showing by a preponderance of 

the evidence that the error was harmless. Id. 4 The error would be harmless 

only if it did not substantially affect Mr. Tony’s rights. See United States 

v. Glover, 413 F.3d 1206, 1210 (10th Cir. 2005) (“In non-constitutional 

harmless error cases, the government bears the burden of demonstrating, by 

 4 In some published cases, we have said that criminal defendants

asserting error bear the burden of proving an effect on their substantial 

rights. United States v. Anaya, 117 F.3d 447, 448–49 (10th Cir. 1997); 

United States v. Mitchell, 113 F.3d 1528, 1532 (10th Cir. 1997); United 

States v. Messner, 107 F.3d 1448, 1453 (10th Cir. 1997); United States v. 

Arutunoff, 1 F.3d 1112, 1118 (10th Cir. 1993). But both before and after 

these cases, we have held that the government bears the burden of showing 

harmlessness. See, e.g., United States v. Rivera, 900 F.2d 1462, 1469 n.4 

(10th Cir. 1990) (“[T]he government ordinarily has the burden of proving 

that a non-constitutional error was harmless.”); United States v. Harrison, 

743 F.3d 760, 764 (10th Cir. 2014) (“In non-constitutional harmless error 

cases, the government bears the burden of demonstrating . . . that the 

substantial rights of the defendant were not affected.” (quoting United 

States v. Keck, 643 F.3d 789, 798 (10th Cir. 2011))).
10

a preponderance of the evidence, that the substantial rights of the 

defendant were not affected.”). 

At trial, Mr. Tony denied premeditation and asserted self-defense. 

The government focuses on the assertion of self-defense, arguing that the 

error was harmless because Mr. Tony could still urge self-defense based on 

Mr. Garcia’s erratic and violent behavior. But the government does not 

address how the methamphetamine evidence might have affected Mr. 

Tony’s denial of premeditation. Without any argument on premeditation, 

the government failed to satisfy its burden on harmlessness. We thus must 

reverse and remand for further proceedings.

VI. The appropriate remedy is vacatur of the conviction, not remand 

for consideration of the government’s pretrial argument for 

exclusion under Rule 403.

Given our need to reverse, we must decide the scope of the remand. 5

Before trial, the government argued in a motion in limine that the 

methamphetamine evidence was inadmissible under both Rule 404(b) and 

Rule 403. Given the exclusion under Rule 404(b), the court never decided 

whether to grant the motion in limine under Rule 403.

 5 In his opening brief, Mr. Tony asked twice for a new trial based on 

the erroneous exclusion of methamphetamine evidence. Appellant’s 

Opening Br. at 3, 39. In one place, Mr. Tony asked us to remand for the 

district court to consider the government’s argument under Rule 403. In a 

supplemental letter, Mr. Tony reiterated that he is seeking a new trial 

(based on the evidentiary error) rather than a remand for consideration of 

the issue under Rule 403.
11

The government timely objected under Rule 403 and ordinarily would 

be entitled to a ruling on this objection. But the government prevailed on 

its other objection, obtaining exclusion of the methamphetamine evidence 

under Rule 404(b). Given this ruling, we must consider whether to 

• remand for the district court to decide the admissibility of the 

methamphetamine evidence under Rule 403 or 

• vacate the conviction and remand for a new trial.

Remanding for the district court to consider the motion in limine would be 

troublesome for two reasons. 

First, the trial took place over two years ago. Deciding the Rule 403 

issue now would require the district court to travel back in time and 

speculate how it would have ruled over two years ago, before hearing the 

trial evidence. 

Second, remanding for consideration of the motion in limine would 

create a dilemma for the district court, which would have an overwhelming 

temptation to rationalize the exclusion of the methamphetamine evidence 

under Rule 403. See Dodge v. Cotter Corp., 328 F.3d 1212, 1229 (10th Cir. 

2003) (“We decline to entertain the possibility of a remand to the district 

court to make specific findings relative to these experts, for we think no 

district court would be well positioned to make valid findings given the 

overwhelming temptation to engage in post hoc rationalization of admitting 

the experts.”). 
12

For both reasons, we conclude that the appropriate remedy is vacatur 

of the murder conviction rather than remand to consider whether to grant 

the motion in limine based on Rule 403. See Ruiz-Troche v. Pepsi Cola of 

Puerto Rico Bottling Co., 161 F.3d 77, 88 (1st Cir. 1998) (deciding that 

“the fairest course,” when evidence of the victim’s cocaine use was 

improperly excluded, was to order a new trial rather than remand for 

consideration of other evidentiary objections); see also Estate of Barabin 

v. AstenJohnson, Inc., 740 F.3d 457, 465–66 (9th Cir. 2014) (en banc) 

(stating that the Court of Appeals would remand for a new trial when the 

district court erroneously excluded evidence even if the district court had 

failed to address a threshold requirement of admissibility).

We thus reverse with instructions to vacate the conviction on firstdegree murder and to conduct a new trial on this charge.