State v. Diaz

IN THE SUPREME COURT OF THE STATE OF IDAHO
Docket No. 47667

STATE OF IDAHO, )
) Boise, November 2021 Term
Plaintiff-Appellant, )
) Opinion Filed: April 6, 2022
v. )
) Melanie Gagnepain, Clerk
RUBEN DANIEL DIAZ, )
)
Defendant-Respondent. )
____________________________________)

Appeal from the District Court of the Fourth Judicial District of the State of Idaho,
Ada County. Jonathan Medema, District Judge.

The district court’s decisions are affirmed.

Lawrence G. Wasden, Idaho Attorney General, Boise, attorney for Appellant.
Kale Gans argued.

Eric D. Fredericksen, State Appellate Public Defender, attorney for Respondent.
Justin Curtis argued.
_________________________________

BEVAN, Chief Justice.
In this permissive appeal, the State challenges the district court’s order denying a motion
to exclude expert testimony that Ruben Daniel Diaz lacked the mens rea to commit aggravated
battery because he suffered from a mental illness or defect that caused him to believe the victim
was not a person but instead an alien being from another planet. The State charged Diaz with
aggravated battery, use of a deadly weapon in the commission of a crime, and resisting and
obstructing a police officer after he stabbed a man in a random attack. The State filed a motion in
limine to exclude Diaz’s expert testimony, arguing Idaho Code section 18-207 bars expert
testimony on evidence of a mental condition. The district court denied (1) the motion in limine,
(2) the State’s subsequent motion to reconsider, and (3) the State’s motion for a permissive appeal.
The State then timely filed a motion for permissive appeal to this Court, which we granted. For
the reasons below, we affirm.

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 I. FACTUAL AND PROCEDURAL BACKGROUND
A. Factual Background
Clyde Gary Vinsonhaler was raking leaves in his front yard when he saw a stranger, Ruben
Daniel Diaz, enter the cul-de-sac in his neighborhood. Vinsonhaler thought Diaz appeared “a little
disoriented and confused,” so Vinsonhaler asked Diaz where he was headed. Vinsonhaler thought
Diaz “might have been in some kind of a convalescent home or something and had gotten out and
was walking the neighborhood and was lost[.]” Diaz said something he “couldn’t quite make out,”
but Vinsonhaler still believed Diaz was “just kind of disoriented” and began to back up to maintain
distance between Diaz and himself.
Vinsonhaler did not feel threatened at this point but wanted to disengage from Diaz and
thought he should go inside and contact police to have an officer “talk to him or help him or take
him away[.]” Vinsonhaler walked across his front yard and through the gate into the backyard
believing he had “left him out in the little side yard out in front of the house.” Vinsonhaler thought
he had time to go inside and call the police to have an officer come out and respond.
As he walked inside to contact police, Vinsonhaler thought he closed and locked the sliding
patio door behind him, but he was not sure. In any event, Vinsonhaler was in the bedroom
searching for the police dispatch number when he heard a noise coming from the hallway. When
he looked into the hallway, he saw Diaz standing inside the house. Diaz “just stood there.”
Vinsonhaler recalled telling Diaz, “You don’t belong here, you need to leave,” but Diaz simply
responded, “no.”
As Vinsonhaler tried to flee the house, he made it to the front door and was standing with
his back to Diaz when he felt something grab him from behind. The next thing Vinsonhaler felt
was what he “thought was a pruning saw cutting my face.” In fact, it was a knife. Diaz stabbed
Vinsonhaler “[a]ll over”—on his face, “around the neck,” and elsewhere, repeatedly saying, “I’m
going to kill you.” Both men wrestled over the knife for several minutes until law enforcement
arrived and subdued Diaz with a taser. Vinsonhaler was severely wounded but survived. Even so,
Vinsonhaler required several surgeries on his hands, face, neck, and throat area.
B. Procedural Background
The State charged Diaz with (1) aggravated battery, (2) use of a deadly weapon in the
commission of a crime, (3) and resisting and obstructing an officer. Later, the State filed an

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Information Part II, and alleged Diaz was a persistent violator. Under Idaho Code 18-207, Diaz
notified the State of his intent to introduce expert testimony at trial. Diaz intended to offer
testimony from Dr. James Davidson “that Mr. Diaz was delusional at the time of the offense and
that, while Mr. Diaz admits slashing and cutting Mr. Vinsonhaler with a knife, Mr. Diaz, at the
time he made the decision to do so, believed Mr. Vinsonhaler was not a person, but was instead an
alien.”
In response, the State moved in limine to exclude the expert’s testimony arguing it was
irrelevant, prejudicial, and advanced a prohibited insanity defense. The district court denied the
State’s motion, holding that the evidence was relevant to prove a mistake of fact defense or
otherwise negate intent. The State then moved for a permissive appeal, which the district court
denied. The State filed a permissive appeal to this Court, which was granted.
II. STANDARD OF REVIEW
“The trial court has broad discretion in the admission and exclusion of evidence and its
decision to admit evidence will be reversed only when there has been a clear abuse of that
discretion.” State v. Lopez-Orozco, 159 Idaho 375, 377, 360 P.3d 1056, 1058 (2015) (quoting State
v. Robinett, 141 Idaho 110, 112, 106 P.3d 436, 438 (2005)). When this Court reviews an alleged
abuse of discretion by a trial court the sequence of inquiry requires consideration of four essentials:
“whether the trial court: (1) correctly perceived the issue as one of discretion; (2) acted within the
outer boundaries of its discretion; (3) acted consistently with the legal standards applicable to the
specific choices available to it; and (4) reached its decision by the exercise of reason.” State v.
Bodenbach, 165 Idaho 577, 591, 448 P.3d 1005, 1019 (2019) (quoting Lunneborg v. My Fun Life,
163 Idaho 856, 863, 421 P.3d 187, 194 (2018)). Whether evidence is relevant is reviewed de novo.
State v. Raudebaugh, 124 Idaho 758, 764, 864 P.2d 596, 602 (1993).
A motion seeking a pretrial ruling on the admissibility of evidence is known as a motion
in limine. Idaho’s courts recognize the importance of a motion in limine. State v. Young, 136 Idaho
113, 120, 29 P.3d 949, 956 (2001). A motion in limine enables a judge to make a ruling on evidence
without first exposing it to the jury. It avoids juror bias sometimes generated by objections to
evidence during trial. The court’s ruling on the motion enables counsel of both sides to make
strategic decisions before trial on the content and order of evidence to be presented. See generally
Warren v. Sharp, 139 Idaho 599, 605, 83 P.3d 773, 779 (2003), overruled on other grounds by
Blizzard v. Lundeby, 156 Idaho 204, 322 P.3d 286 (2014). Since a motion in limine is based on an
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alleged set of facts rather than the actual testimony, the trial court’s ruling is not a final order. Id.
The trial court may reconsider the issue at any time, including when the actual presentation of facts
is made. Id.

III. ANALYSIS
A. We affirm the district court’s decision denying the State’s motion to exclude the
expert testimony of Dr. Davidson.
The State challenges the district court’s order denying its motion to exclude expert
testimony, arguing the testimony was (1) irrelevant and inadmissible under Idaho Code section 18-
207, (2) addressed an unavailable mistake of fact defense, and (3) was otherwise highly prejudicial.
We affirm the district court’s order.
1. Expert testimony that Diaz did not know his victim was human was relevant to
establish the elements of aggravated battery.
The district court denied the State’s motion in limine to exclude expected expert testimony
from Dr. Davidson who would state that Diaz lacked the requisite mens rea to commit aggravated
battery because he suffered from a mental disease or defect that caused him to believe the victim
was an alien. Davidson planned to opine: “Mr. Diaz was delusional at the time of the attack and
that, while Mr. Diaz admits slashing and cutting Mr. Vinsonhaler with a knife, Mr. Diaz . . .
believed Mr. Vinsonhaler was not a person, but was instead an alien.” The district court found
Davidson’s testimony was relevant, explaining in the order denying the State’s motion to
reconsider that Idaho Code section 18-903(a) and 18-907(b) required the State to “prove that a
person willfully used force or violence upon the person of another and that the person had no
lawful justification for doing so.” According to Idaho Code section 18-903, which Diaz was
charged under:
A battery is any:
(a) Willful and unlawful use of force or violence upon the person of another; or
(b) Actual, intentional and unlawful touching or striking of another person against the will
of the other; or
(c) Unlawfully and intentionally causing bodily harm to an individual.
I.C. § 18-903. Subsection (a) requires the State to prove a person acted willfully. Diaz was also
charged with aggravated battery—with the use of a deadly weapon or battery that caused great
bodily harm. See I.C. § 18-907. Thus, at its core, as the district court correctly observed, this case

4
turns on what state of mind the State must prove the defendant had when committing battery. If
the only state of mind required is that the defendant acted willfully, then expert testimony that Diaz
lacked capacity to form intent is irrelevant. On the other hand, if the state of mind is something
more—that the defendant knowingly performed the willful action—his alleged incapacity to form
intent would be relevant.
Evidence is admissible only if it is relevant, and “relevant evidence” means “evidence
having any tendency to make the existence of any fact that is of consequence to the determination
of the action more probable or less probable than it would be without the evidence.” I.R.E. 401.
“Irrelevant evidence is not admissible.” I.R.E. 402.
Though Idaho abolished the insanity defense, “Section 18-207, Idaho Code, does not
prevent a defendant from presenting relevant evidence of his mental state.” State v. Beam, 109
Idaho 616, 621, 710 P.2d 526, 531 (1985). Thus, Idaho Code section 18-207(3) does not “prevent
the admission of expert evidence on the issue of any state of mind which is an element of the
offense, subject to the rules of evidence.” State v. Fisher, 162 Idaho 465, 467, 398 P.3d 839, 841
(2017) (quoting I.C. § 18-207(1)). In fact, evidence of mental condition is still expressly permitted
to rebut the State’s evidence offered to prove criminal intent or mens rea.
Idaho Code § 18-207 does not remove the element of criminal responsibility for the
crime. The prosecution is still required to prove beyond a reasonable doubt that a
defendant had the mental capacity to form the necessary intent. Idaho Code § 18-
207 merely disallows mental condition from providing a complete defense to the
crime and may allow the conviction of persons who may be insane by some former
insanity test or medical standard, but who nevertheless have the ability to form
intent and to control their actions. The statute expressly allows admission of expert
evidence on the issues of mens rea or any state of mind which is an element of the
crime.
State v. Samuel, 165 Idaho 746, 770, 452 P.3d 768, 792 (2019) (quoting State v. Card, 121 Idaho
425, 430, 825 P.2d 1081, 1086 (1991)). “Whether the accused possessed the necessary intent to
commit the offense is a question for the finder of fact.” State v. Oxford, 167 Idaho 515, 523, 473
P.3d 784, 792 (2020). Thus, any expert testimony admitted on the issue of mens rea or state of
mind under Idaho Code section 18-207, must speak to an element of the crime. See Card, 121
Idaho at 430, 825 P.2d at 1086; I.C. § 18–207(3).
Diaz argues that Idaho Code section 18-903(a) requires the State to prove that an accused
willfully used force or violence on a person without justification. Diaz also suggests his intent
when he committed the crime is relevant because Idaho Code section 18-207(3) specifically
5
permits a defendant to present evidence of a mental disease or defect that would negate intent. The
State acknowledges it must prove “force or violence” was inflicted on the “person of another”
under Idaho Code section 18-903(a) but maintains it need not also prove Diaz subjectively believed
his victim was human. The State argues that because knowledge is not an element of aggravated
battery under Idaho Code section 18-903(a), it need not prove Diaz subjectively knew his victim
was human and as such, expert testimony that Diaz thought his victim was an alien was irrelevant
and inadmissible under Idaho Code section 18-207.
The distinction between “willful” and “knowing” is an important one. Both terms speak to
the mental state the State must meet in a criminal case. Idaho Code section 18-101(1) explains that
“[t]he word ‘wilfully,’ when applied to the intent with which an act is done or omitted, implies
simply a purpose or willingness to commit the act or make the omission referred to. It does not
require any intent to violate law, or to injure another, or to acquire any advantage.” On the other
hand, “[t]he word ‘knowingly,’ imports only a knowledge that the facts exist which bring the act
or omission within the provisions of this code. It does not require any knowledge of the
unlawfulness of such act or omission.” I.C. § 18-101(5).
Considering these two mental states, the district court explained:
The state’s argument here is that there was a purposeful and willful use of
force or violence and that was clearly on the person of another. The question is
simply, is it sufficient for the state to show that [Diaz] purposefully used force or
violence upon something that turns out to be a person, or does the state have to
show that he knew it was a person when he chose to use force or violence upon it?
And I think that’s the crux of this issue.
Indeed, that is the crux of the issue. And we conclude the State must show Diaz knew his
victim was a person when he chose to use force or violence, not merely that he used force or
violence upon something that turned out to be a person, as the district court explained. Here, expert
testimony that Diaz suffered from a mental disease rendering him unable to make that distinction
is, therefore, relevant. Diaz intended to put forth expert testimony from Davidson that “Diaz, due
to his delusions, believed that he was attacking an alien.” The State, for its part, must prove Diaz
intended to attack a person—not an alien.
According to Idaho Code section 18-114, “[i]n every crime or public offense there must
exist a union, or joint operation, of act and intent, or criminal negligence.” The ‘intent’ as used in
that section of the statute is construed to mean, “not an intent to commit a crime but is merely the

6
intent to knowingly perform the interdicted act . . . .” State v. Parish, 79 Idaho 75, 78, 310 P.2d
1082, 1083 (1957) (quoting State v. Taylor, 59 Idaho 724, 87 P.2d 454, 460 (1939)).
For aggravated battery, the state of mind required is that one willfully use force or violence
against another. The statute does not, however, identify the requisite state of mind that one must
possess while willfully using that force against another person. In other contexts, we have held
that knowledge is an implied element of the offense, even though the statute does not expressly
require knowledge. See State v. Parish, 79 Idaho at 79, 310 at 1083 (“knowledge is an essential
element of the [traffic] offense, though the statute does not expressly require knowledge”); State
v. Bishop, 146 Idaho 804, 816, 203 P.3d 1203, 1215 (2009) (interpreting Idaho Code section 18-
705 as having three elements, one of which is that the defendant knew when resisting arrest that
the officer was trying to perform an official duty).
We reach the same conclusion here. Although the plain language of the statute does not
explicitly require the State show Diaz had knowledge that his actions would willfully injure
another human, we hold that knowledge is implied from the statute and must be proven to sustain
a conviction for the same.
The Idaho Court of Appeals has examined two cases involving the intent required for
aggravated battery, which Diaz submits support his position and the district court’s decision. In
State v. Billings, 137 Idaho 827, 54 P.3d 470 (Ct. App. 2002), a defendant “aimed his shotgun to
the right” of the victim and “fired into the ground.” Id. at 828, 54 P.3d at 471. Pellets “ricocheted
off the ground” and struck the victim. Id. The State charged Billings with aggravated assault and
aggravated battery. Id. The State argued “the only intent the State was required to prove was that
Billings intended to fire the shotgun.” Id. at 829, 54 P.3d at 472. The court rejected that argument;
instead, to prove aggravated battery, the State needed to prove that Billings intended the shotgun
pellets to strike the victim. Id. at 830, 54 P.3d at 473. Even so, the court found there was sufficient
evidence to support the knowledge element because Billings’ intent could be inferred. Id. at 831,
54 P.3d at 474. The court explained the nature of the shotgun was one that fired scores of pellets,
and that Billings knew that if the pellets hit the ground, “when there’s gravel and stuff there, they
can ricochet.” Id. As a result, while there was no direct evidence that Billings intended to shoot his
victim directly, the court held there was sufficient evidence that he was aware that some pellets
would hit the victim, which was enough to meet the willfulness standard under Idaho Code section
18-903(a). Id.
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 Then, in State v. Pole, 139 Idaho 370, 79 P.3d 729 (Ct. App. 2003), the Court of Appeals
again considered the requisite mental state for battery under Idaho Code section 18-903(a). Pole
fired a .357 caliber pistol into the exterior wall of his apartment. Id. at 371, 79 P.3d at 730. Before
discharging the weapon, Pole had pointed the gun at two of his roommates and suggested they
play Russian roulette. Id. When the roommates declined, Pole turned and fired a round through the
adjacent wall, hitting someone behind the wall in the adjoining apartment. Id. Pole was unaware
the apartment was occupied when he fired the gun, but the bullet that went through the wall
paralyzed the victim. Id. The Idaho Court of Appeals explained why Pole’s conduct did not amount
to aggravated battery:
In this case, the evidence presented at the preliminary hearing failed to show
that Pole knew the adjacent apartment bedroom was occupied at the time and that
Pole intended that someone bear the brunt of the force or violence caused by the
firing of the handgun. The evidence showed that Pole willfully pulled the trigger.
However, the evidence did not show that Pole knew the victim was on the other
side of the wall at the time.

Id. at 375, 79 P.3d at 734.
Diaz does not dispute that he committed an act that resulted in force or violence against
another person, but according to the proposed expert testimony from Davidson, Diaz did not intend
force or violence against a person. While the State argues that it need not prove Diaz’s subjective
beliefs, we find Diaz’s argument more persuasive; the State cannot show that he intended a forceful
or violent contact against another person if they cannot show he knew the subject of his attack is
human.
Our decision today aligns with both Pole and Billings. Pole intended to shoot the wall, not
another person, and the evidence did not show Pole knew the anyone was on the other side when
he shot the wall. Billings intended to shoot another person, because he knew that if he shot the
ground, the pellets would ricochet and hit his victim. The rationale underpinning both cases bolster
our decision here that the pertinent fact is whether the defendant intends to use force or violence
against another person. Here, we cannot conclude that expert testimony on whether Diaz intended
to injure another person is irrelevant.
Both Diaz and the State also point this Court to Kansas’s mens rea defense, which, like
Idaho, does not allow the insanity defense but does permit a defendant to introduce evidence of
mental illness if it negates intent. In State v. Pennington, 132 P.3d 903 (Kan. 2006), which the

8
State relies on, the defendant was charged with a general intent crime, and the defendant argued
the lower court erred by excluding testimony from an expert that the defendant suffered a “serious
delusional disorder,” and his intent was “formed based on delusional thinking.” Id. at 913. The
Kansas Supreme Court held that such an argument was precluded by its mens rea approach
identified in its statute:
The problem with this argument is that under the mens rea approach, it is
no longer relevant whether intent is formed rationally or whether it is formed based
on delusions. As the [Kansas] Court of Appeals’ majority correctly recognized,
intent formed on the basis of delusions may have provided a defense under the prior
insanity approach, but not under the mens rea approach.
Id. at 908. The State argues the same logic applies here, adding: the question is not why Diaz acted
the way he did, whether his decisions made rational sense, or what he subjectively thought about
objective facts when he chose to act. Rather, the State proposes the question of whether Diaz
willfully and purposefully acted to stab the victim. Diaz admits he did.
In Kahler v. Kansas, 140 S.Ct. 1021 (2020), a second case Diaz relies on, the U.S. Supreme
Court affirmed the Kansas mens rea defense. Notably, the Supreme Court explained:
Kansas law provides that it is “a defense to a prosecution” that “the defendant, as a
result of mental disease or defect, lacked the culpable mental state required” for a
crime. That provision enables a defendant to present psychiatric and other evidence
of mental illness to defend himself against a criminal charge. More specifically, the
defendant can use that evidence to show that his illness left him without the
cognitive capacity to form the requisite intent.
Id. at 1030 (citation omitted). We agree that Kansas’s law is instructive, but we diverge from
Kansas’s approach in focusing solely upon the general versus specific intent distinction that its
supreme court relied on in Pennington. Kansas’s authority does not benefit the State here because
the U.S Supreme Court noted the difference we note today. Based on the facts here, Davidson’s
proffered testimony suggests that Diaz’s mental illness left him without the capacity to form the
requisite intent. This holding reflects the mens rea defense recognized by both Kansas and Idaho.
Idaho Code section 18-207 “expressly allows admission of expert evidence on the issues of mens
rea or any state of mind which is an element of the crime.” State v. Samuel, 165 Idaho 746, 770,
452 P.3d 768, 792 (2019) (quoting State v. Card, 121 Idaho 425, 430, 825 P.2d 1081, 1086 (1991)).
For these reasons, we affirm the district court’s decision that expert testimony from
Davidson on whether Diaz believed Vinsonhaler was human was relevant.
2. Mistake of fact is an available defense to aggravated battery.

9
 Next, the district court found that the “State must prove Mr. Diaz knew he was using force
on a person. Knowledge is a required element of the crime. Thus, a mistake of fact that disproves
that knowledge is a defense under [s]ection 18-201 and 18-207.” In reaching this conclusion, the
district court also explained:
[T]he legislature intended mistake of fact to be an available defense if the person,
when the person chose to do the prohibited act, had a mistaken knowledge of some
fact that disproves the mental state required to be guilty of the offense. Similarly[,]
the legislature made clear in Section 18-207, that mental defect is a defense to any
crime if it disproves the state of mind required to be guilty. I.C. § 18-207. “Criminal
intent” in Section 18-201 does not automatically mean “intention,” i.e., a desire to
achieve a specific result. Criminal intent in Section 18-201 means the “state of
mind” a person must have to be guilty of the crime, as the legislature defined it.
The district court clarified, “some crimes…require [] that to be guilty of that crime a
defendant, when the defendant acts, must have a specific mental intention, i.e., a desire that the
doing of the act will produce a particular result, either directly or by making it possible for the
defendant to do some additional act.” To that end, the district court reasoned that Section 18-201
and Section 18-207 permit Diaz to introduce the evidence “because [the] evidence concerns the
state of mind which is an element of battery—knowledge that the actor is applying force or
violence to another human.” Thus, the district court correctly recognized the correlation between
a mens rea defense and the available mistake of fact defense to seek to establish a lack of mens
rea. This defense is a logical extension of the knowledge requirement addressed above.
Diaz claims that under the plain language of Idaho Code sections 18-201(1) and 18-207(3),
mistake of fact is not limited to specific intent crimes. Instead, Diaz submits both statutes permit
the defense so long as the proffered defense disproves “any criminal intent” or “any state of mind
which is an element of the offense.” The State contends that the defense would not negate any
criminal intent, borrowing an analogy used by the district court of a hunter who mistakenly shoots
a person believing the person was a deer. The State suggests that the hunter might reasonably claim
such a use of force on the person was negligent, rather than willful, but that Diaz’s proposed
defense is not that he mistakenly used force or violence on the person, but that he did so
intentionally.
The mistake of fact defense is authorized by Idaho Code section 18-201, which states, in
part:
All persons are capable of committing crimes, except those belonging to the
following classes:
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 1. Persons who committed the act or made the omission charged, under an
ignorance or mistake of fact which disproves any criminal intent.
....
I.C. § 18-201(1). Additionally, “I.C. § 18-207(c) specifically provides that a defendant is not
prohibited from presenting evidence of mental disease or defect which would negate intent.” State
v. Beam, 109 Idaho 616, 621, 710 P.2d 526, 531 (1985). What we must discern is how Idaho Code
sections 18-201(1) and 18-207(3) intersect, if at all, with aggravated battery.
Crimes in Idaho are categorized as either “general intent” or “specific intent” crimes. State
v. Stiffler, 117 Idaho 405, 406, 788 P.2d 220, 221 (1990). Aggravated battery is considered a
general intent crime. “A general criminal intent requirement is satisfied if it is shown that the
defendant knowingly performed the proscribed acts. . . but a specific intent requirement refers to
that state of mind which in part defines the crime and is an element thereof.” State v. Guerra, ___
Idaho ___, ___, 497 P.3d 1106, 1123 (2021) (quoting State v. Gowin, 97 Idaho 766, 767–68, 554
P.2d 944, 945–46 (1976)). Whether a crime is a specific or general intent crime is a distinction
“that has existed in our law throughout this century. This Court has [at times] relied on this
distinction in determining when ignorance or mistake of fact is a defense under I.C. § 18–201(1).”
Stiffler, 117 Idaho at 410, 788 P.2d at 225. Even so, as we discuss below, the distinction is not all-
encompassing; this Court has tempered the distinction in explicit ways and we do so again in our
holding today.
Neither party here contests that aggravated battery is a general intent crime. See State v.
Carlson, 134 Idaho 389, 400, 3 P.3d 67, 78 (Ct. App. 2000) (“This form of battery, in Idaho, is a
general intent crime.”). The only question is whether mistake of fact is an available defense to
aggravated battery. We conclude that it is, so long as the mistake of fact is a reasonable one. See,
e.g., State v. Diaz, 44 Kan. App. 2d 870, 874–75, 241 P.3d 1018, 1022 (2010) (explaining the
principle that a reasonable mistake of fact may be asserted as a defense to a general intent crime);
State v. Kelsey, 331 S.C. 50, 77, 502 S.E.2d 63, 77 (1998) (explaining that mistake of fact is an
available defense only if the defendant can show a reasonable basis for having made the mistake);
Diaz first suggests, as did the district court below, that mistake of fact is an available
defense to aggravated battery because this Court allowed the defense for another general intent
crime: possession of a controlled substance. See State v. Lamphere, 130 Idaho 630, 945 P.2d 1
(1997). While this Court has permitted mistake of fact as a defense in such cases, we have done so

11
case-by-case when knowledge was recognized as a required element of the offense, even though
the crime may be characterized as a “general intent” crime. Thus, a mistake of fact defense is
available to negate the intent element in a limited subset of cases. As we concluded above, we now
recognize knowledge as an element of aggravated battery. Since that is the case, a reasonable
mistake of fact is an available defense in the very limited circumstances when knowledge that the
victim is not a person is a tenable issue of fact.
Diaz submits that this Court’s decision to permit a mistake of fact defense for a general
intent crime like possession of a controlled substance, like in Lamphere, suggests that mistake of
fact is available for aggravated battery. This is an overly broad characterization that we do not
adopt. We have explained before that a mistake of fact defense is available only when the offense
is one where specific criminal knowledge is an element of the crime. When such knowledge is not
an element of the offense, the lack of knowledge or mistake of fact surrounding that element is
irrelevant. See State v. Sterrett, 35 Idaho 580, 583, 207 P. 1071, 1072 (1922) (for illegal
transportation of liquor, a general intent crime, “the good intentions and good faith of the person
transporting the liquor is immaterial.”). Yet because we hold that knowledge is an element of
aggravated battery, we must also hold that a reasonable mistake of fact is an available defense to
negate that element when an accused’s knowledge is at issue.
In State v. Fox, 124 Idaho 924, 866 P.2d 181 (1993), this Court discussed the mental state
that was an element of possession of a controlled substance as defined in Idaho Code section 37-
2732(c). Idaho Code section 37-2732(c) does not expressly require any mental element, and Idaho
Code section 18-114 requires only general intent. Id. at 926, 866 P.2d at 183. Even so, the
defendant claimed he did not know it was illegal to possess the drugs he had, not that he was under
a mistaken belief that he possessed them. Id. We declined to extend a mistake of fact defense to
those facts because Fox was actually claiming mistake of law. Id.
Then, in Lamphere, this Court permitted mistake of fact as a proper defense for a defendant
charged with possession of methamphetamine. We distinguished the case from Fox because
Lamphere’s defense was that he did not know what was in the vial he possessed, and testimony
about his knowledge was, therefore, relevant to his possession charge. 130 Idaho at 633, 945 P.2d
at 4. We also permitted a mistake of fact jury instruction in State v. Blake if the defense could
prove the defendant believed the substance under Blake’s seat was a harmless substance rather
than methamphetamine or cocaine. 133 Idaho 237, 242, 985 P.2d 117, 122 (1999).
12
 Thus, while these cases establish a line of general intent crimes in which knowledge is an
element, these results have been limited to a narrow category of crimes based on our interpretation
of the relevant statutes. See, e.g., State v. Bishop, 146 Idaho 804, 816, 203 P.3d 1203, 1215 (2009)
(explaining that a defendant is guilty of willfully resisting if the defendant knew the person was
an officer); Lamphere, supra. Alternatively, we elected not to read a knowledge requirement into
the statutory rape statute (Idaho Code section 18-6101(1)) because proof that a defendant had
sexual intercourse with a victim who was under the age of eighteen was sufficient; the defendant’s
knowledge of the victim’s age was irrelevant. Stiffler, 117 Idaho at 406, 788 P.2d at 221. We
explained, “[i]f we were to determine that statutory rape requires only general intent, mistake of
age would not be a defense, since any mistake of age would not disprove that Stiffler had sexual
intercourse with a female under the age of eighteen.” Id.
While the State argues that Stiffler’s logic equally applies here, whether Diaz subjectively
thought of the victim as a “person” or not, the distinction we draw lies in the differing mens rea
elements between the two crimes. An accused can be convicted of violating the statutory rape
statute whether he knows of the victim’s age or not; an assailant who willfully inflicts an injury
(as here) upon a person he believes is not a human (due to an issue with his state of mind), may
present this defense “to the jury so it may decide where the truth lies.” Washington v. Texas, 388
U.S. 14, 19 (1967). Thus, the line of cases that encompass statutory rape and sexual assault are
distinct from the offense here. We have noted as much before. See State v. Herr, 97 Idaho 783,
788–89, 554 P.2d 961, 966–67 (1976) (“Sexual offenses against minors have long been a
recognized judicial exception to the general rule that a mistake of fact is a defense to a criminal
charge.”). And because of that, the sexual assault cases do not guide our inquiry today.
The interpretation we announce aligns with how other jurisdictions have examined the
distinction we now delineate. In New Mexico, for example, its Supreme Court addressed when
mistake of fact is an available defense, explaining:
[The mistake of fact defense] is merely a restatement in somewhat different form
of one of the basic premises of the criminal law. Instead of speaking of. . . mistake
of fact. . . as a defense, it would be just as easy to note simply that the defendant
cannot be convicted when it is shown that he does not have the mental state required
by law for commission of that particular offense.
State v. Bunce, 861 P.2d 965, 968, n.3 (N.M. 1993). See also People v. Crane, 585 N.E.2d 99, 102
(Ill. 1991) (internal quotations omitted) (“Mistake of fact is a valid defense if the mistake negates

13
“the existence of the mental state which the statute prescribes with respect to an element of the
offense.”); State v. Sexton, 733 A.2d 1125, 1129 (1999) (quoting State v. Cavness, 911 P.2d 95,
99–100 (Haw. App. 1996) (“[I]f a person is ignorant or mistaken as to a matter of fact. . . the
person's ignorance or mistake will, in appropriate circumstances, prevent the person from having
the requisite culpability with respect to the fact. . . as it actually exists.”). We adopt and follow this
reasoning as consistent with Idaho Code section 18-207(3) and our holding above about the mens
rea required to prove an aggravated battery.
The proposed defense Diaz seeks to put forward is that he was mistaken as to whether the
being he stabbed was human. This defense is available to Diaz as he seeks to negate the state of
mind relevant to the offense.
3. The district court did not abuse its discretion in determining the testimony would
be admissible under Rule 403.
Finally, the State argues that even if the testimony is relevant, the district court should have
excluded the proposed evidence as unfairly prejudicial under Idaho Rule of Evidence 403. Diaz
contends he has a constitutional right to present a defense, which is protected by the Sixth and
Fourteenth Amendments and that excluding Davidson’s testimony would violate his right to
present a defense.
The right to present a defense is protected by the Sixth Amendment of the United States
Constitution and made applicable to the states through the due process clause of the Fourteenth
Amendment. Washington, 388 U.S. at 19. “This right is a fundamental element of due process of
law.” Id. The right to present a defense includes the right to offer testimony of witnesses, compel
their attendance, and to present the defendant’s version of the facts “to the jury so it may decide
where the truth lies.” Id. All the same, this right must be balanced against any interest the State
has in the criminal trial process; “the Sixth Amendment ‘does not confer the right to present
testimony free from the legitimate demands of the adversarial system.’” State v. Albert, 138 Idaho
284, 287, 62 P.3d 208, 211 (Ct. App. 2002) (quoting Taylor v. Illinois, 484 U.S. 400, 412–13
(1988)). Nor is a defendant free to present a defense based on irrelevant evidence. State v. Meister,
148 Idaho 236, 241, 220 P.3d 1055, 1060 (2009) (“A defendant has no right to present irrelevant
evidence and even if evidence is relevant, it may be excluded in certain cases.”).
The Rules of Evidence strike the appropriate balance by protecting the trial court’s
discretion to limit relevant evidence if the probative value is “substantially outweighed by the

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danger of unfair prejudice, confusion of the issues, or misleading the jury, or by considerations of
undue delay, waste of time, or needless presentation of cumulative evidence.” I.R.E. 403. “This
rule, however, does not require the exclusion of all prejudicial evidence, but only that which is
unfairly prejudicial such that it tends to suggest a decision on an improper basis.” State v. Moore,
131 Idaho 814, 819, 965 P.2d 174, 179 (1998). “The standard is not ‘extraordinarily’ prejudicial,
but ‘unfairly’ prejudicial.” State v. Russo, 157 Idaho 299, 309, 336 P.3d 232, 242 (2014).
As a result, the district court’s determination of whether the probative value of evidence is
substantially outweighed by unfair prejudice is reviewed for an abuse of discretion. State v.
Ehrlick, 158 Idaho 900, 926, 354 P.3d 462, 488 (2015). When this Court reviews an alleged abuse
of discretion by a district court, it analyzes whether the district court: “(1) correctly perceived the
issue as one of discretion; (2) acted within the outer boundaries of its discretion; (3) acted
consistently with the legal standards applicable to the specific choices available to it; and (4)
reached its decision by the exercise of reason.” State v. Bodenbach, 165 Idaho 577, 591, 448 P.3d
1005, 1019 (2019) (quoting Lunneborg v. My Fun Life, 163 Idaho 856, 863, 421 P.3d 187, 194
(2018)).
Below, the district court rejected the State’s argument that jurors would feel sympathetic
for Diaz and acquit him despite his guilt if the court permitted Diaz to present Davidson’s opinion
that Diaz did not know Vinsonhaler was a person when Diaz stabbed him. In the district court’s
ruling, it concluded that such an argument “fails to give jurors the trust they are due.” To that end,
the district court explained it “will almost certainly instruct jurors that neither sympathy nor
prejudice may influence their deliberations. This court believes the vast majority of jurors work
diligently to follow the court’s instructions and those who do not have their behavior curbed by
others.” In reaching this conclusion, the district court did not discuss specific portions of
Davidson’s opinion. Instead, the district court addressed Davidson’s report generally.
The State suggests that, even if the “court’s sense that the juror’s ‘feelings of sympathy’
would not be improperly stirred by the expert testimony,” Davidson’s opinion still invited jurors
to decide the case on an improper basis. Davidson’s report contained four opinions on Diaz’s
mental state:
1. It is my opinion that Mr. Diaz’ psychotic thought process was present
preceding, during and after the alleged offense
2. It is my opinion that Mr. Diaz’ psychotic thought process, when present, is
symptomatic of schizophrenia, paranoid type, a mental condition rooted in
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 neurobiological dysfunction that profoundly directs the thinking of an
individual rather than a volitional condition. This opinion is supported by
reports of bizarre functional behavior by Mr. Diaz, his mother, jail medical staff
and deputy reports, police reports and witness statements of the alleged instant
offense, and my assessment.
3. It is my opinion that Mr. Diaz, due to his delusion, believed that he was
attacking an alien. He did not recognize or understand that he was attacking a
human being.
4. It is my opinion that, as a result of severe mental disease or defect, Mr. Diaz
suffered from a defect in reason and was unable to appreciate the nature and
quality or wrongfulness of his acts at the time of the offense. In other words, at
the time of alleged offense as a result of mental disease or defect he lacked
substantial capacity either to appreciate the criminality/wrongfulness of his
conduct or to conform his conduct to the requirement of the law.
As to the fourth opinion, the State contends that this opinion was unfairly prejudicial because it
suggested the jury resolve the case under an incorrect legal standard.1 The State suggests that
Davidson’s opinion was almost a verbatim quote from Idaho’s former insanity defense, and that
his opinion asked jurors to consider the case with a standard Idaho explicitly rejected when it
abolished the insanity defense. The State’s argument has some merit on its face, but it appears the
district court has yet to conclusively rule on Davidson’s opinion number 4, and there are additional
failings to the State’s argument on appeal.
First, we note that the State failed to identify which prong of the abuse of discretion
standard the district court allegedly did not meet. While this Court does not impose a “formalistic
requirement that the standard of review be recited and the party claiming error attack a particular
prong of that standard of review,” the State failed to even acknowledge in passing that the district
court’s decision was one of discretion. Such a failure is generally fatal to such an argument. See
State v. Jeske, 164 Idaho 862, 870, 436 P.3d 683, 691 (2019) (explaining a failure to recite the
standard of review is not fatal but the parties must argue the district court violated the abuse of
discretion standard); Cummings v. Stephens, 160 Idaho 847, 853, 380 P.3d 168, 174 (2016)

1
The Act adopting Idaho Code section 18-207 repealed the former versions of Idaho Code sections 18-207, 18-208,
18-209, 18-213 and 18-214. 1982 Idaho Session Laws, ch. 368, at 919. Former Idaho Code section 18-207 set forth
the elements of the insanity defense in Idaho as the following: Mental illness as defense—(1) A person is not
responsible for criminal conduct if at the time of such conduct as a result of mental disease or defect he lacks
substantial capacity either to appreciate the wrongfulness of his conduct or to conform his conduct to the requirements
of law. (2) As used in this act, the terms “mental disease or defect” do not include an abnormality manifested only by
repeated criminal or otherwise anti-social conduct. This test is largely the same required by Idaho Code section 19–
2523.
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(“[Appellant] makes no attempt to address the matters we consider when evaluating a claimed
abuse of discretion.”); State v. Kralovec, 161 Idaho 569, 575, n.2, 388 P.3d 583, 589, n.2 (2017)
(“We note that this Court has seen an increasing number of cases where a party completely fails
to address the factors we consider when evaluating a claimed abuse of discretion.”).
Next, juries are presumed to follow the instructions given by the court. State v. Carson,
151 Idaho 713, 718, 264 P.3d 54, 59 (2011). The State points to no evidence in the record to
overcome this presumption other than to suggest this Court “[p]ut aside for a moment the court’s
sense that the jurors’ ‘feelings of sympathy’ would not be improperly stirred by the expert
testimony[.]”
Further, the State fails to point to any indication that the district court intended to admit the
limited portion (opinion number 4) the State challenges, or that the district court did not recognize
the proper legal standard. Although the above-referenced portion of Davidson’s opinion could
confuse jurors by “asking the jurors to consider this case with the standard that Idaho specifically
rejected when it abolished the insanity defense,” the district court did not suggest it would allow
Davidson to testify to opinion number 4. At the motion for reconsideration hearing, the district
court stated as the hearing began:
I’ll start with the [S]tate’s motion asking me to reconsider my denial of the [S]tate’s
motion to exclude testimony by Dr. Davidson on the basis that it was not relevant.
That’s what I think I’m here to decide today; although, there was some language in
the [S]tate’s briefing that seemed to suggest, the [S]tate viewed that I had made
decisions differently than that, that I had made some decision about the ultimate
admissibility of Dr. Davidson’s opinions, or that I had made some rulings as to
what the jury would be instructed, which I have not.
As a result, the State’s argument for what the jury might consider and what the district court
could allow is too speculative for us to make a definitive ruling at this stage in the proceedings. As
noted above, the district court’s ruling, as a decision in limine, remains subject to change at trial.
Warren v. Sharp, 139 Idaho 599, 605, 83 P.3d 773, 779 (2003), overruled on other grounds by
Blizzard v. Lundeby, 156 Idaho 204, 322 P.3d 286 (2014).
The State finally argues Davidson’s opinion carried a risk of sympathy overwhelming the
jury’s impartial consideration of the issues. The State asserts that if a jury were to hear an expert
state that Diaz “lacked substantial capacity” to “appreciate the criminality/wrongfulness of his
conduct,” this opinion would engender too much sympathy for Diaz by the jury. To that end, the

17
district court explained, “[t]he court will almost certainly instruct the jurors that neither sympathy
nor prejudice may influence their deliberations.” And:

This court also believes it is unlikely jurors will be strongly moved to feel sympathy
towards Mr. Diaz if they conclude that he randomly and violently attacked a
stranger on the street simply because Dr. Davidson opines that Mr. Diaz’s chronic
behavior falls within one of the multitude of labels that psychiatrists use as a short-
hand way to describe abnormal behavior patterns.
We agree with the district court’s observations. As a result, we hold the district court did not abuse
its discretion in finding the testimony about mens rea was not unfairly prejudicial.

V. CONCLUSION
For these reasons, we affirm the district court’s decisions to deny the State’s motion in
limine and to permit a mistake of fact defense.
Justices BRODY, STEGNER, MOELLER and Justice pro tem HORTON, CONCUR

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