State of Minnesota, Respondent,

This opinion is nonprecedential except as provided by
Minn. R. Civ. App. P. 136.01, subd. 1(c).

STATE OF MINNESOTA
IN COURT OF APPEALS
A21-0996

State of Minnesota,
Respondent,

vs.

Nathan Sims,
Appellant.

Filed June 20, 2022
Affirmed
Cochran, Judge

Ramsey County District Court
File No. 62-CR-20-3568

Keith Ellison, Attorney General, St. Paul, Minnesota; and

John J. Choi, Ramsey County Attorney, Alexandra Meyer, Assistant Coun ty Attorney,
St. Paul, Minnesota (for respondent)

Cathryn Middlebrook, Chief Appellate Public Defender, Jessica Merz Godes, Assistant
Public Defender, St. Paul, Minnesota (for appellant)

Considered and decided by Cochran, Presiding Judge; Bryan, Judge; and
Gaïtas, Judge.
NONPRECEDENTIAL OPINION
COCHRAN, Judge
In this direct appeal from his convic tion of unintentional second-degree murder,
appellant argues that the district court abused its discretion by admitting expert testimony
regarding gunshot-residue-testing evidence. We affirm.
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FACTS
This case involves the shooting death of J. C. The following is a summary of the
evidence presented at trial.
Late one night in May 2020, J.C. and his girlfriend, A.J., were riding their bikes in
St. Paul. Both homeless, J.C. and A.J. headed toward the home of A.J.’s friend, hoping to
spend the night. The couple was arguing and arrived separately at the house—A.J. arrived
at approximately 12:15 a.m., and J.C. arrive d about four minutes later. Several other
people were present at the house that night, including appellant Na than Sims. Sims had
recently been staying at the house and sleeping on the couch in the front room.
After A.J. arrived, she agreed to go to the garage with her friend, the homeowner,
to smoke a cigarette. As they walked toward the garage, A.J. and the homeowner heard a
loud noise. Next they heard J.C. yelling that he had been shot. Scared by the shooting, the
homeowner went inside the house. There, he saw Sims standing in the front room of the
house. The homeowner asked Sims “if it was him that shot” J.C., and Sims said “no.”
Meanwhile, A.J. went to the front yard to s ee if “[J.C.] was okay” and saw J.C. running
down the street. A.J. followed J.C. down the street. She caught up to him after he sat down
in a driveway. He was holding his chest and cr ying. A.J. saw that J.C. had been shot.
After a neighbor called 911, the police ar rived and rendered fi rst aid until medics
transported J.C. to the hospital. Doctors attempted emergency surgery, but J.C. was
pronounced dead approximately an hour afte r arriving at the hospital. The medical
examiner ruled J.C.’s death a homicide fro m blood loss due to a gunshot wound to the
chest.
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After the shooting and before police arrive d on the scene, some of the people who
were at the house where the shooting occurred left. Other individu als, including Sims,
stayed and were detained by police. Police brought Sims to the St. Paul police headquarters
and interviewed him around 8:00 a.m. that morning. During the interview, police swabbed
Sims’s hands for gunshot residue. Officers had not “bagged” Sims’s hands following his
arrest, meaning they had not covered his hands to preserve any potential evidence on them.
Sims’s hands therefore remained uncovered during the time between his arrest and the
collection of the gunshot-residue evidence. Th e swabs were sent to a criminal forensics
laboratory for testing.
Police also searched the house and the su rrounding area. They found a spent shell
casing on the ground near the front steps of the home, a 9mm Glock handgun and magazine
in the bushes in the backyard, and a 9mm bullet underneath the couch on which Sims had
been sleeping. The serial numbers on the handgun had been ground off. Forensic testing
determined that the shell casing found next to the front steps was fired from the handgun.
A single DNA profile matching Sims was found on the grips, slide, and muzzle of the gun.
A number of weeks after th e shooting, police made contact with one of the people
who had left the house after the shooting on March 29. That individual, N.D., told police
that he saw Sims shoot J.C., and he identified Sims in a photo lineup.
Respondent State of Minnesota charged Sims with second-degree intentional
murder under Minn. Stat. § 609 .19, subd. 1(1) (2018), and second-degree unintentional
felony murder under Minn. Stat. § 609.19, subd. 2(1) (2018). Before trial, Sims moved to
suppress evidence of the “gunshot residue test” and “any e xpert testimony regarding said
4
tests” on the basis that expert testimony on the topic would not “a ssist the jury” under
Minnesota Rule of Evidence 702 and any evidence of the gunshot-residue testing would be
unfairly prejudicial under Minnesota Rule of Evidence 403. The state opposed the motion.
After hearing oral argument on the motion, th e district court denied Sims’s request to
exclude the evidence.
The case then proceeded to a jury trial. A central issue at trial was the identity of
the person who shot J.C. The state intr oduced video clips fro m surveillance cameras
belonging to the homeowner’s next-door neighbor. One clip depicted the shooting of J.C.,
but the camera was angled in such a way that the shooter could not be seen. The state
presented the testimony of N.D. , among other witnesses. N.D. stated that he saw Sims
shoot J.C. from the front steps of the house. The surveillance video showed that N.D. was
standing near the driveway of the house at the time of the shooting. A.J. and the
homeowner, who did not see the shooting, each testified that they saw Sims with a handgun
in the days preceding the shooting. The homeowner stated that he saw Sims grinding the
serial numbers off a handgun in the homeowner’s garage a day or two before the shooting.
A.J. testified that she and J.C. had stopped over at the house a few nights before the
shooting and saw Sims at the house with a “Glock” in his hand.
The state also presented the expert testim ony of a forensic scientist, Tarah Helsel,
who conducted the gunshot-residue testing of the swabs from Sims’s hands. Helsel
explained generally that scientists perfo rming gunshot-residue testing look for two
different types of particles. The first type is three-component particles, which are particles
containing three metals—lead, barium, and antimony—together in a single particle.
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Three-component particles are considered “characteristic” of gunshot residue because they
“are highly specific to the discharge of a firearm” and “there are very few other sources of
those particles.” The second ty pe of particle that scientis ts look for is two-component
particles. Two-component par ticles are those that contain just two of the three metals—
lead/antimony, lead/barium, or barium/a ntimony. Those partic les are considered
“consistent” with gunshot residue, rather than characteristic of it, because they may “come
from the discharge of a firearm” but may also come from other sources such as “brake pads
and fireworks.”
Regarding the gunshot-residue testing in this case, Helsel testified that she did not
identify any three-component particles on the samples from Sims’s hands. However, she
did find multiple two-component particles in the samples. In the sample from Sims’s right
hand, Helsel identified three lead/antimony particles. In the sample from Sims’s left hand,
Helsel identified two lead/antimony particles and one barium/antimony particle. She also
testified that the samples fro m both of Sims’s hands “contai ned one particle that was
barium with high amounts of aluminum” and that those types of particles are also
“consistent” with gunshot residue. Helsel opined that, beca use the particles from Sims’s
hands were two-component particles rather than three-component particles, “they could be
gunshot residue, but they also could be from another source.” After the state rested, Sims
waived his right to testify.
At the conclusion of the trial, the jury acquitted Sims of second-degree intentional
murder but found him guilty of second-degree unintentional murder. This appeal follows.
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DECISION
Sims contends that the district court ab used its discretion by admitting the expert
testimony concerning the gunshot-residue-testing evidence. This court reviews a district
court’s evidentiary rulings, including the decision to admit expert testimony, for an abuse
of discretion. State v. Garland , 942 N.W.2d 732, 742 (Minn. 2020). “A district court
abuses its discretion when its decision is based on an erroneous view of the law or is against
logic and the facts in the record.” Id. (quotation omitted). Appellant “bears the burden of
showing that an abuse of discretion occu rred and that he was prejudiced by it.”
Dolo v. State, 942 N.W.2d 357, 362-63 (Minn. 2020).
Sims challenges the decision to admit th e expert testimony on two grounds. He
argues that the testimony was inadmissible becaus e (1) it was not “helpful” to the jury as
required under rule 702, and alternatively (2) it should have been excluded under rule 403
because its probative value “if any” was s ubstantially outweighed by the danger of unfair
prejudice, confusion of the issues, and mislea ding the jury. The state counters that the
expert testimony was admissible under both rules of evidence and that, even if the evidence
was inadmissible, any error was harmless. For the reasons set forth below, we agree with
the state.
Rule 702
Rule 702 governs the admissibility of expert testimony. It states:
If scientific, technical, or other specialized knowledge
will assist the trier of fact to understand the evidence or to
determine a fact in issue, a w itness qualified as an expert by
knowledge, skill, experience, training, or education, may
testify thereto in the form of an opinion or otherwise. The
7
opinion must have foundational re liability. In addition, if the
opinion or evidence involves novel scientific theory, the
proponent must establish th at the underlying scientific
evidence is generally accepted in the relevant scientific
community.

Minn. R. Evid. 702 (emphasis added). The supreme court has held that for expert testimony
to be admissible under rule 702 it must satisfy a four-part test: “(1) [t]he witness must
qualify as an expert; (2) the expert’s opinion must have foundation al reliability; (3) the
expert testimony must be helpful to the trier of fact; and (4) if the testimony involves a
novel scientific theory , it must satisfy the Frye-Mack standard.” Doe v. Archdiocese of
St. Paul, 817 N.W.2d 150, 164 (Minn. 2012); see also Minn. R. Evid. 702.
Sims’s argument under rule 702 relates so lely to the third re quirement—that the
expert testimony must be helpful to the trier of fact. Expert testimony meets the helpfulness
requirement if it “will assist the trier of fact to understa nd the evidence or to determine a
fact in issue.” Minn. R. Evid. 702; see State v. Vang, 774 N.W.2d 566, 576 (Minn. 2009)
(“The ultimate question of admissibility under Rule 702 is whether the expert’s testimony
will help the jury evaluate evidence or resolve factual issues.” (quotation omitted)). But
“[e]xpert testimony is not helpful if the expert opinion is w ithin the knowledge and
experience of a lay jury and the testimony of the expert will not add precision or depth to
the jury’s ability to reach conclusions.” Garland, 942 N.W.2d at 746 (quotation omitted).
Sims asserts that Helsel’s testimony was not helpful to the jury because the evidence
demonstrated only that his hands containe d two-component particles, rather than
three-component particles. He argues that the presence of two-co mponent particles does
not make it more likely that he fired a gun on the day of the shooting, and that “[i]t is only
8
the combination of all three elements (antimony, barium, and lead) in one particle . . . that
makes ‘the possibility appear more likely’ that a person fired a gun.” On this basis, he
contends that the district court abused its discretion when it concluded that the expert
testimony was admissible under rule 702. We are not persuaded.
In State v. Loving, the supreme court addressed the admissibility of expert testimony
regarding gunshot-residue testing. 775 N.W.2d 872, 877-79 (Minn. 2009). There, Loving
challenged the district court’s decision to admit expert testimony about gunshot-residue
testing of a coat found in his car after a shooting. Id. at 876-77. Loving argued that the
expert testimony was not helpful to the ju ry under rule 702 because the import of the
evidence “was merely that Loving may or may not have discharged or handled a gun, may
or may not have been in close proximity to a discharging gun, or the coat may or may not
have touched or been touc hed by something or someone with [gunshot residue].” Id. at
878. The supreme court rejected Loving’s argument, concluding that the expert testimony
was helpful because, although the evidence “did not definitively establish that Loving fired
a gun, the evidence made that possibility appear more likely than if the test had been
negative.” Id. at 879.
Applying the same reasoning here, Helsel’s expert testimony was helpful to the jury
based on a combination of two reasons. First, the testimony about gunshot-residue testing
was helpful to the jury because gunshot-residue testing is not with in the knowledge and
experience of a lay jury. See Garland , 942 N.W.2d at 746 (explaining that “[e] xpert
testimony is not helpful if the expert opinion is within the knowledge and experience of a
lay jury.” (quotation omitted)). Second, Helsel’s testimony assisted the jury in determining
9
an important fact at issue in the case: whether Sims fired a gun on the day of the shooting.
Although the evidence indica ted that Sims’s hands cont ained only tw o-component
particles, rather than three-component particles—and did not conclusively demonstrate that
Sims fired a gun on that day—the evidence of two-component particles nonetheless makes
that possibility appear more likely than if the test had been negative. See id. I t w a s
therefore helpful to the jury to know the results of the gunshot-residue tests, and it was up
to the jury to determine the weight of that evidence. See Behlke v. Conwed Corp. , 474
N.W.2d 351, 357 (Minn. App. 1991) (“Where an expert is qualified and his or her opinion
has a relevant basis, the credibility and weight of the testimony is to be decided by the
jury.”), rev. denied (Minn. Oct. 11, 1991).
Sims argues that Loving is inapposite to the present case because Loving involved
only the admission of three -component particles, not two- component particles. This
argument misses the mark. A close reading of Loving indicates that the gunshot-residue
evidence at issue in that cas e consisted of both two- and three-component particles. See
Loving, 775 N.W.2d at 876 (noting that two- and three-component particles were found on
Loving’s coat and addressing whether “the distri ct court abused its discretion when . . . it
ruled that testimony about gunshot residue found on the coat from Loving’s car was
admissible”). In any event, the supreme court’s reasoning in Loving applies equally to two-
and three-component particles because both types of test results make it appear more likely
that the defendant fired a gun “than if the test had been negative.” Id. at 879. In other
words, Loving provides guidance in this case because it delineates when expert testimony
10
about gunshot-residue-testing evidence will assist the trier of fact. As explained above, the
evidence in this case meets the Loving standard.
We therefore conclude that the district court did not abuse its discretion by
determining that Helsel’s expert testimony was admissible under rule 702.
Rule 403
Sims next argues that rule 403 provides an alternative basis for reversal. He
contends that the district court abused its discretion by not excl uding Helsel’s expert
testimony under rule 403. Rule 403 provides that “[a]lthough relevant, evidence may be
excluded if its probative value is substan tially outweighed by the danger of unfair
prejudice, confusion of the issues, or misleadi ng the jury, or by c onsiderations of undue
delay, waste of time, or needless presentati on of cumulative eviden ce.” Minn. R. Evid.
403. Expert testimony may be excluded under rule 403 ev en if it is otherwise admissible
under rule 702. See Doe, 817 N.W.2d at 164 (stating that expert testimony must satisfy
both rule 702 and rule 403).
Sims contends that Helsel’s expert testimony had “minimal to no probative value”
and “any probative value was substantially outw eighed by the danger of unfair prejudice,
confusion of the issues, and misleading the jury.” On this basis, he contends that the district
court should have excluded the testimony.
Regarding the probative value or lack thereof, Sims raises two arguments. First,
similar to his argument concerning rule 702, Sims emphasizes that the evidence
demonstrated that his hands contained only two-component particles, which could have
come from a source other than the discharge of a firearm such as brake pads or fireworks.
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Second, Sims argues that the probative value of the evidence was “further reduced” by the
risk that the two-component particles found on his hands were the product of contamination
from the law enforcement enviro nment. He notes that po lice did not “bag” his hands
following his arrest to prevent the possibility of contamination and that his hands were not
swabbed for gunshot residue until “several hour s” after his arrest. He asserts that the
two-component particles could have transf erred to his hands from handcuffs, police
officers, the back seat of the squad car in which he was transported, or various surfaces at
the police station.
Sims next argues that the risk of unfair prejudice, confusion of the issues, and the
jury being misled was high because Helsel’s testimony “obscured the distinction between
gunshot residue and what was actually found on Sims’[s] hands.” He asserts that Helsel’s
testimony “fluctuated between using the words ‘two’ and ‘three’ when testifying about
‘metals,’ ‘elements,’ ‘particles,’ and ‘hands’” and that “[a]ny lay jury hearing scientific
testimony about gunshot residue analysis for the first time would be confused by Helsel’s
various statements that sounded similar but in fact were extremely nuanced and meant
critically different things.” We are not persuaded by any of his arguments.
The expert testimony concerning the gunsho t-residue testing had probative value
because it was relevant to determining whether Sims fired a gun on the day of the shooting.
Although the evidence of two-component particles was not conclusive proof that Sims fired
a gun, and although the police’s failure to “bag” Sims’s hands upon his arrest may have
increased the risk of contamination, the e xpert testimony that two-component particles
12
were found on Sims’s hands still makes it more likely that Sims fired a gun on the day in
question.
Further, our review of the record convinces us that the probative value of the expert
testimony was not substantially outweighed by the potential for unfair prejudice, confusion
of the issues, or misleading th e jury. The record belies Sims’s contention that Helsel’s
testimony “obscured” the distinction between two-compon ent particles and
three-component particles. At trial, Hels el explained generally that three-component
particles are considered “characteristic” of gunshot residue because there are “very few
other sources of those particles,” while two-component particles are considered
“consistent” with gunshot residue because they may come from other sources such as brake
pads and fireworks. Helsel th en explained that all of the particles found on the samples
from Sims’s hands were two-co mponent particles, and she st ated both on direct and
cross-examination that she did not find any three-component particles on the samples. She
further clarified that the particles from Sims’s hands “could be gunshot residue, but they
also could be from another source” and she “[could not] say for certain that they are gunshot
residue because they are lacking that third el ement.” Considered as a whole, Helsel’s
testimony clearly explained that the particles found on the samples from Sims’s hands were
two-component particles which are “consistent” with gunshot residue and may have come
from a source other than a firearm. We are not persuaded that Helsel’s testimony confused
or misled the jury.
Moreover, Sims’s attorney took advantage of the opportunity on cross-examination
to ask both Helsel and a police officer in volved in swabbing Sims’s hands about the
13
possibility of contamination. This additional testimony aided the jury in determining the
weight to assign to the gunshot-residue evidence in light of the potential for contamination.
In sum, the record reflects that Helsel’s expert testimony was probative of whether
Sims fired a gun on the day in question, and that probativ e value was not substantially
outweighed by the danger of unfair prejudice , confusion of the issues, or misleading the
jury. The district court did not abuse its discretion when it admitted the expert testimony.
Harmless Error
The state also argues that, even if Helsel’s expert testimony was inadmissible under
either rule 702 or 403, reversal is not warranted because any error was harmless. We need
not address this argument because we have already concluded that the district court did not
abuse its discretion when it admitted the challenged expert testimony. But, even assuming
error by the district court in admitting the te stimony, Sims has not demonstrated grounds
for reversal. See Dolo, 942 N.W.2d at 362-63.
An evidentiary error is ha rmless unless it “substantially influenced the jury’s
decision.” Vang, 774 N.W.2d at 576 (quotation omitted ). Here, even without the expert
testimony, other substantial and compelling evidence of Sims’s guilt was presented at trial.
The jury heard eyewitness tes timony from N.D., who stated th at he saw Sims shoot J.C.
from the front steps of the house. Ballistic evidence connected a shell casing found near
the front steps of the house to a handgun recovered from the bushes in the backyard. And
forensic analysis revealed a single DNA prof ile matching Sims on th e grips, slide, and
muzzle of the gun. Two witnesses further testified that they saw Sims with a gun matching
the description of that weapon in the days preceding the shoo ting. Given the substantial
14
record evidence of Sims’s guilt even without the challenged testimony, there is no basis to
conclude that admission of the expert tes timony substantially influenced the jury’s
decision.
Conclusion
The district court acted well within its di scretion when it concluded that Helsel’s
expert testimony was admissible. Sims has failed to demonstrate grounds for reversal
under either rule 702 or rule 403. Moreov er, even assuming an abuse of discretion in
admitting the expert testimony, any error was harmless in light of the other substantial
evidence of Sims’s guilt presented at trial.
Affirmed.