Later, questioning became more pointed. Williams was asked, "Do you think that law enforcement knows that you were involved in -- in [Fleming's] death?" Williams acknowledged at that point that he had shot Fleming in the parking lot of the Clarkview Apartments. He said that he had been approaching the Chevy Equinox when Fleming "said something that triggered him." Williams said he was standing a few feet from the open window of the car when he shot Fleming. He shot "however many bullets he had in his gun." Williams also admitted he "never saw [Fleming] with a gun that night."
*625Williams admitted that after he shot Fleming, he opened the car door, pulled Fleming out, and got into the vehicle and drove away. Williams said that he later broke Fleming's cellphone into pieces and threw them away. He also retrieved two shell casings from the car and discarded the gun he had used to shoot Fleming. Williams said he had purchased the gun from Ed Brown and had kept it under the sink in his apartment.
Williams went on with this version of events. He claimed that earlier that evening of June 30, when Fleming, Williams, and others were hanging out at the apartment complex, Fleming had questioned the group whether they had something to do with a beating Fleming had recently received. Before Fleming left in his vehicle, he allegedly told others in the group, "You better not be standing here when I get back." Williams told the investigator he went to retrieve his gun after Fleming left. Williams added that he should have let the matter go. As Williams put it, "I did it, I did it, and I shouldn't have done it."
Williams did not claim in the interview that he had acted in self-defense. To the contrary, he said, "[I]t's on me. That's on me."
An autopsy report determined that Fleming died from multiple gunshot wounds. Fleming's body contained six gunshot wounds, which were caused by between four and six bullets. Four bullets were recovered from Fleming's body. One of the wounds had gunpowder stippling, which meant that the gun had been discharged within eighteen inches of Fleming's body. Fleming's blood alcohol concentration at the time of his death was .242.
On July 19, a trial information was filed in the Iowa District Court for Floyd County, charging Williams with first-degree murder. See Iowa Code §§ 707.1, .2(1)(a ). On August 24, Williams moved to change the venue from Floyd County. On September 11, the district court denied the motion, indicating that the majority of the media articles had been factual and that it did not believe prospective jurors would have a predisposition about the case. The court did instruct the clerk, however, to bring in an additional jury panel to ensure there would be sufficient numbers from which to select a jury. On September 18, Williams filed a notice that he intended to rely on the defense of self-defense/justification at trial. See id. § 704; Iowa R. Crim. P. 2.11(11)(c ).
Trial was scheduled to begin October 10. On October 2, Williams, who is African-American, filed a motion to challenge the jury panel. Williams's motion noted that African-Americans represent 2.3% of the Floyd County population according to the 2016 census, yet only two of the 166 potential jurors who submitted questionnaire responses for two jury pools for October through December 2017 self-identified as African-American. (One of these two had been excused.) Williams also reported tallies for the last four years:
In the calculations overall in the [last] four years, there were 1,404 jurors, of which, 452 did not respond to the race question. Of the 952 remaining jurors, in this four-year span, only 9 members reported being African American, which would be only 0.9% of the jurors pooled from 2013 through 2017.
On October 3, the State filed a resistance to Williams's motion. The State acknowledged that the most recent census data showed that 2.3% of the population in Floyd County was Black or African-American, but argued this figure should not be used for comparisons because the African-American population was disproportionately younger and 2.3% did not reflect the percentage actually eligible for jury service. The State also urged the *626data on which Williams relied were flawed because they did not account for jurors who declined to disclose their race on their questionnaire responses. The State thus insisted that Williams had not proved substantial underrepresentation or systematic exclusion under the three-part Duren / Plain standard. See Duren v. Missouri , 439 U.S. 357, 364, 99 S. Ct. 664, 668, 58 L.Ed.2d 579 (1979) ; State v. Plain , 898 N.W.2d 801, 822 (Iowa 2017).
On October 5, the district court held a hearing on pretrial motions at which it received exhibits and heard argument on the motion to strike the jury panel. On October 6, the district court entered a written ruling denying Williams's motion to challenge the jury panel. The court found that Williams failed to show a violation of his Sixth Amendment rights under the second and third prongs of the Duren / Plain test. The court noted,
Turning to the panels available for the defendant's trial the Court required the clerk to call in two separate pools. According to Exhibit D, the last two pages, there were 103 letters sent to potential jurors in Pool 1 and 103 letters sent to potential jurors in Pool 2. Twelve letters were either undelivered or did not respond as to Pool 1. Thus there were 91 responses in Pool 1. In Pool 2 there were five that were undelivered or failed to respond. There were 98 responses in Pool 2.
In Pool [1] there are 23 potential jurors who did not identify their ethnicity. The 23 number is derived from adding the three who responded, the nine who were excused, and the ten who were disqualified, and the one who was deferred. Subtracting 23 from 91 results in 68 potential jurors who responded and self-identified their ethnicity. In Pool 2, of the 98 responses, 28 responses did not self-identify their ethnicity (six responding, 14 excused, six disqualified, and two deferred). Subtracting 28 from 98 results in 70 potential jurors who responded and self-identified their ethnicity.
Combining the two pools results in 138 individuals who responded to their summons and who self-identified their ethnicity. Exhibit D demonstrates that there is one self-identified African-American who was excused from the jury. The Court understands that the reason for the excusal is because the individual was attending college away from home. Panel 2 has one person [who] identified as African-American.
If the jury pool was proportional to the population, out of 138 jurors, there should be two to three potential jurors who are African-American. If the Court accepts the defendant's figure of 2.3 percent, then the number of expected African-American jurors in the pool should be at least three jurors.
The district court went on to reject Williams's argument that the excused African-American juror could not be considered because "there is no showing that the method of excusing jurors is such that African-Americans are excused in greater numbers than other persons of different ethnicity or nationality." The court then found no underrepresentation because given the small numbers involved, "it is difficult to apply a rigid statistical analysis to the matter." The court also held there was no showing of systematic exclusion of African-Americans from the potential jury pool. It noted, however,
In reviewing historical numbers, the Court believes that the state court system can do more and the Court suspects that a more through statistical analysis would show that African-Americans are less likely to have motor vehicle registration or are less likely to be registered to vote. However, that showing has not *627been made in this case. The Court believes that additional lists could be used to increase the potential numbers of distinct minority groups. However, while believing there may be better ways to select potential jurors, this does not mean that the current method systematically excludes African-American jurors. The State attempts to use neutral, readily-available lists. Defendant's position does not address potential other reasons for the potential underrepresentation of African-Americans on the historical jury pools. There is not sufficient showing that a systematic exclusion resulted from something that the State has done.
Trial began as scheduled on October 10. Two days earlier, Williams had moved for individualized voir dire by counsel "so that the Defendant can effectively and adequately exercise his peremptory challenges in selecting jurors." For most of the day of the 10th, the court, the prosecution, and the defense conducted voir dire, and a number of prospective jurors were excused. In the afternoon, the defense approached the court and specifically requested taking each of the thirty-four prospective jurors in the box for a private interview to talk to them about their attitudes regarding race, among other things. The State opposed the request. The district court ruled,
THE COURT: All right. I'm going to overrule that motion. One, for the reasons stated by the State. I -- We've listened to this jury, and I think most of them have expressed an opinion that they can be fair and impartial and don't have any predisposition in -- in this matter. And just from that kind of general sampling, I don't think it's going to be necessary to have an individual examination.
The second reason is just a matter of -- of timing. Five minutes each -- and I think that's generous -- times 34 is 170 minutes, which is, you know, almost three hours. And if we take some breaks here and there for the court reporter, you know, basically we'd be using a half a day for that.
We have a shot of getting the jury selected today. I don't know if that's going to happen or not. My experience is if I have 150 people having to come back overnight, we lose some of them, there might be exposure to things that we don't want to have them exposed to. It's a lot easier if I have 14 people that I have to take care of -- and keep track of.
So I don't want to spend that time in order to -- to pick a jury, given all that; and also I -- I think it's somewhat unfair to -- to the jury members that we do that without, you know, more cause shown for doing that.
Williams's counsel proceeded to voir dire the jurors concerning racial attitudes as a group. For example, she asked, "If you're picked to be on the jury and you go back to the jury room and you hear another juror making an argument based on race, what would you do?"
During the defense case, Williams presented witnesses who testified that Fleming had a disagreeable and boastful personality and had got into an altercation earlier that month and threatened retaliation. Witnesses also testified that Fleming was driving recklessly, had tried to slap a woman, and was making threats on June 30. Witnesses also testified to Williams's peaceful disposition.
Additionally, Williams testified on his own behalf and gave a different version of events than he had provided after his arrest. According to Williams, earlier in the day on June 30, Fleming was driving recklessly through the Clarkview Apartments parking lot, acting aggressively, insulting people, and making threats. Williams *628claimed the threats included the use of firearms.
Williams testified he obtained the gun he used to shoot Fleming from a friend, i.e., Brown, earlier on June 30 because he was fearful of Fleming. However, Brown denied at trial he had provided the gun to Williams. Brown said he had previously seen Williams with a gun.
Williams claimed that when he approached Fleming in the Chevy Equinox on the evening of June 30, Fleming was highly agitated and had his music on loud, and Williams was trying to calm him down. According to Williams, Fleming said to him, "Man, you know what, don't even approach my m__f__ing car," and accused him of being in association with the individuals who had recently beaten up Fleming. After some exchanges back and forth, in Williams's words, "[H]e started reaching for what I thought was a gun." At this point, Williams said he pulled the gun out of his back pocket, covered his face, and fired shots at Fleming repeatedly until the gun was empty. Williams claimed he covered his face the entire time that he was shooting Fleming, although all the shots apparently hit their mark. Williams also claimed that when he pulled Fleming out of the car, "I didn't think he was really hurt ...."
Even at trial, Williams admitted that he never saw a gun on Fleming's person:
Q. Did you ever see a weapon in the car? A. I -- I don't know. I didn't check for one, though. That -- That's my answer.
Q. Did you see a weapon in the car? A. I did not check for one, sir.
Q. Well, did you see Mr. Fleming with a weapon? A. You're just trying to switch this on me; but no, sir.
On October 18, the jury returned a verdict finding Williams guilty of the lesser included offense of murder in the second degree. See Iowa Code § 707.3. On December 8, the court sentenced Williams to an indeterminate term of imprisonment of fifty years with a mandatory seventy percent minimum. See id. § 707.3(2) ; id. § 902.12. Williams filed a notice of appeal, and we retained the appeal.
On appeal, Williams raises five arguments. First, he contends that he was denied his constitutional right to a jury panel drawn from a fair cross section of the community. Second, he contends the district court abused its discretion in not allowing individualized voir dire of potential jurors on race-related issues. Third, he maintains the district court erred in excluding evidence of Fleming's criminal history and prior acts of violence not known by Williams. Fourth, Williams insists that the district court erred in refusing to give his proposed jury instruction on implicit bias. Finally, Williams contends the court erred in not following the stand your ground amendment that was enacted in 2017 and became effective on July 1 of that year.
III. Standard of Review.
We review constitutional questions de novo. Plain , 898 N.W.2d at 810. This includes claims of systematic exclusion of a distinctive group from a jury pool in violation of the Sixth Amendment. See id.
We review claims of voir dire error for an abuse of discretion. State v. Martin , 877 N.W.2d 859, 865 (Iowa 2016). Likewise, evidentiary rulings are reviewed for an abuse of discretion. State v. Huston , 825 N.W.2d 531, 536 (Iowa 2013). This includes rulings on the admission or exclusion of evidence regarding prior bad acts. State v. Putman , 848 N.W.2d 1, 7 (Iowa 2014). Additionally, we review the refusal to give a cautionary jury instruction for abuse of discretion. See *629Plain , 898 N.W.2d at 811. We have described the abuse-of-discretion standard as follows:
When assessing a district court's decision for abuse of discretion, we only reverse if the district court's decision rested on grounds or reasoning that were clearly untenable or clearly unreasonable. Grounds or reasons are untenable if they are "based on an erroneous application of the law or not supported by substantial evidence."
Id. (quoting State v. Dudley , 856 N.W.2d 668, 675 (Iowa 2014) ).
"We review rulings on questions of statutory interpretation for correction of errors at law." State v. Childs , 898 N.W.2d 177, 181 (2017) (quoting State v. Iowa Dist. Ct. , 889 N.W.2d 467, 470 (Iowa 2017) ).
IV. Fair-Cross-Section Claim.
The jury that convicted Williams had no African-Americans on it. It also appears there were no African-Americans on the October 10 panel that was seated in the courtroom and went through voir dire. Williams maintains that the jury selection process used in Floyd County violated his Sixth Amendment right to have a jury drawn from a fair cross section of the community.1
As noted, the district court found that Williams had failed to meet either the second or the third Duren / Plain prong. It observed that out of 138 individuals in the combined pool, there were only two self-identified African-Americans, but it was "difficult to apply a rigid statistical analysis to the matter" in light of "the small numbers involved." It also found no showing that a particular State practice had resulted in systematic exclusion.
In two other cases decided today, we have discussed what a defendant must prove to establish a fair-cross-section constitutional violation. See *630Lilly , --- N.W.2d at ---- ; Veal , --- N.W.2d at ----. As we have explained, under the second Duren / Plain prong, the percentage of the distinctive group in the population should be determined using the most recent available census data. See Lilly , --- N.W.2d at ---- ; Veal , --- N.W.2d at ----. These data may be adjusted to account for those who are actually eligible to serve as jurors, for example, by eliminating the population that is under eighteen and the population (if any) that is incarcerated in a state prison located in the county. See Lilly , --- N.W.2d at ---- ; Veal , --- N.W.2d at ----.
For Sixth Amendment purposes, the defendant must then show that the percentage of the group in the jury pool is less than this expected percentage by at least two standard deviations. See Veal , --- N.W.2d at ----. Pools may be aggregated, so long as pools closer in time to the trial date are not omitted when earlier pools are included. See Lilly , --- N.W.2d at ---- ; Veal , --- N.W.2d at ----. The aggregation of pools can help solve the "small numbers" problem observed by the district court in its thoughtful ruling.
Once underrepresentation has been shown, the defendant must then show that some practice or practices caused the underrepresentation-i.e. the third Duren / Plain prong. See Lilly , --- N.W.2d at ---- ; Veal , --- N.W.2d at ----. As we have explained in Veal , for Sixth Amendment purposes, the practice must be something more than an item on the Berghuis v. Smith "laundry list." Veal , --- N.W.2d at ---- (quoting Berghuis v. Smith , 559 U.S. 314, 332, 130 S. Ct. 1382, 1395, 176 L.Ed.2d 249 (2010) ).
To illustrate how this analysis might work, in this case one African-American juror was excused from even coming to the courthouse on October 10 because she was in college. Williams argues that she and other preexcused jurors should not be counted in determining the percentage of the distinctive group in the jury pool, making the ratio 1/130 rather than 2/138. The State and the district court viewed the matter otherwise. As the State reasons, there is no reason to omit persons who received a juror summons from the statistics, "especially in the absence of any allegation that hardship excusals are granted in patterns that contribute to underrepresentation or exclusion."
There is a potential problem with the State and the district court's position, at least under article I, section 10 of the Iowa Constitution. A policy or practice relating to excusing jurors might amount to systematic exclusion. See Lilly , --- N.W.2d at ----. If a defendant wishes to try to prove that it does, the defendant should not be foreclosed from doing so by a rigid rule that calculates the pool based on who was summoned, rather than who actually appeared.2
In this case, the district court prepared a careful ruling based on the caselaw as it existed at the time of trial. But it did not have the benefit of today's decisions. As in Lilly and Veal , we believe the appropriate course of action is to remand to give Williams a further opportunity to develop his Sixth Amendment fair-cross-section claim using the criteria we have set forth today. See Lilly , --- N.W.2d at ---- ; Veal , --- N.W.2d at ----.
V. Individualized Voir Dire on Racial Attitudes.
Williams next argues that he is entitled to a new trial because his attorneys were unable to conduct individualized voir dire of the potential jurors on race issues outside the presence of the other potential *631jurors. The weight of authority places this subject within the domain of trial court discretion, at least when the case does not have particular racial overtones. See, e.g., United States v. Parker , 872 F.3d 1, 7, 8 (1st Cir. 2017) ("[N]o authority exists to support Parker's theory-floated during oral argument-that if the case facts suggest the judge should voir dire on race, then only an individual voir dire will do."); United States v. Hosseini , 679 F.3d 544, 555 (7th Cir. 2012) ("[O]rdinarily, questioning jurors as a group is sufficient to satisfy the Sixth Amendment, even when the defendant belongs to a racial, ethnic, or religious minority and juror bias on one or more of these grounds might be a concern."); People v. Harris , 57 Cal.4th 804, 161 Cal.Rptr.3d 364, 306 P.3d 1195, 1220 (2013) (finding no abuse of discretion in denying the defendant's motion for individual sequestered voir dire on race); Commonwealth v. Robinson , 78 Mass.App.Ct. 714, 942 N.E.2d 980, 986 (2011) (finding that individual voir dire regarding racial bias was not required because the case did not involve an alleged interracial killing, interracial rape, or sexual offense against a child by a defendant of a different race); Smith v. State , 977 So. 2d 1227, 1237 (Miss. Ct. App. 2008) (finding no error in denial of the defendant's motion for sequestered voir dire on attitudes toward race).
In State v. Windsor , a case involving an African-American defendant and a white alleged victim, we held that
trial courts in Iowa should make or permit counsel to make specific inquiry into racial prejudice upon proper request in similar circumstances and in any case in which a reasonable possibility exists that the verdict might be affected by racial prejudice.
316 N.W.2d 684, 686-87 (Iowa 1982). Yet we also held that "absent special circumstances of the nature delineated in Ham [v. South Carolina , 409 U.S. 524, 93 S. Ct. 848, 35 L.Ed.2d 46 (1973) ], the inquiry may be limited to a question of the panel sufficient to call the jurors' attention to the subject and require response from any juror harboring racial bias."3 Id. at 687. In State v. Oshinbanjo , our court of appeals followed in Windsor 's tracks and held that a district court did not abuse its discretion in denying "defendant's request to individually question prospective jurors out of the presence of the other jurors" on the subject of racial prejudice. 361 N.W.2d 318, 321 (Iowa Ct. App. 1984).
Williams asks us, in effect, to overrule Windsor . He argues that several decades have passed and there has been new scholarship on implicit bias. But Williams cites no scholarship directed to the specific issue here-namely, the effectiveness of questioning prospective jurors on race in an individual, sequestered setting as opposed to a group setting.
On our review of the record, we find the district court did not abuse its discretion. The defendant and the decedent were of the same race and there is no suggestion that race played a role in the alleged crime or its investigation. Additionally, the district court balanced Williams's request against other concerns. This case had received some notoriety in this county of around 16,000 people. The district court noted that if it granted individualized voir dire, it would no longer be possible to *632finish jury selection that day.4 The court worried that it would be more difficult to limit the exposure of a large group of potential jurors overnight to improper influence than to limit the exposure of a small group of actual jurors: "It's a lot easier if I have 14 people [twelve jurors and two alternates] that I have to take care of and -- keep track of." There is logic to the court's reasoning. The message that people need to act responsibly tends to be better received when those people have been given responsibility. Thus, a person who has been told she or he is an actual juror may be more prone to take the court's admonition seriously. Finally, we note that defense counsel's panel questioning on the subject of race was thoughtful and insightful.
Having said that, we emphasize that this was a murder trial where the defendant faced a very severe sentence. Defense counsel should be given considerable leeway in utilizing voir dire to eliminate potential racial bias from the jury.
VI. Implicit-Bias Instruction.
At trial, the district court gave Jury Instruction 5, which stated in part,
As you consider the evidence, do not be influenced by any personal sympathy, bias, prejudices or emotions. Because you are making very important decisions in this case, you are to evaluate the evidence carefully and avoid decisions based on generalizations, gut feelings, prejudices, sympathies, stereotypes, or biases. The law demands that you return a just verdict, based solely on the evidence, your reason and common sense, and these instructions. As jurors, your sole duty is to find the truth and do justice.
However, the court denied Williams's request to give the following additional instruction:
Our system of justice depends on judges like me and jurors like you being able and willing to make careful and fair decisions. Scientists studying the way our brains work have shown that, for all of us, our first responses are often like reflexes. Just like our knee reflexes, our mental responses are quick and automatic. Even though these quick responses may not be what we consciously think, they could influence how we judge people or even how we remember or evaluate the evidence.
Scientists have taught us some ways to be more careful in our thinking that I ask you to use as you consider the evidence in this case:
Take the time you need to test what might be reflexive unconscious responses and to reflect carefully and consciously about the evidence.
• Focus on individual facts, don't jump to conclusions that may have been influenced by unintended stereotypes or associations.
• Try taking another perspective. Ask yourself if your opinion of the parties or witnesses or of the case would be different if the people participating looked different or if they belonged to a different group
• You must each reach your own conclusions about this case individually, but you should do so only after listening to and considering the opinions of the other jurors, who may have different backgrounds and perspectives from yours.
*633Working together will help achieve a fair result.[5 ]
The court noted that Williams's proposed instruction had not been reviewed by any Iowa court to its knowledge. The court also pointed out that Instruction 5 in its view covered the subject matter:
Instruction 5 does talk about setting aside stereotypes, biases, and prejudices. I think that addresses the issue. The law -- The jury's otherwise instructed to consider what they've heard in the courtroom; and -- and if they follow those instructions, then the race of the -- of the defendant or the -- or Mr. Fleming would not be pertinent. I'm aware of the concerns; but, as I said, I think Instruction 5 addresses that matter.
Williams argues on appeal that the district court's refusal of his implicit-bias instruction amounted to reversible error.
In Plain , the district court declined to give a different implicit-bias instruction than the one Williams requested here. 898 N.W.2d at 816. We noted in Plain that denial of a cautionary instruction like an implicit-bias instruction is subject to an abuse-of-discretion standard. Id. We held the trial court had abused its discretion "because it erroneously believed it lacked authority from our court to give the [implicit-bias] instruction." Id. at 817. Yet, in the end, we found that the district court's refusal to give Plain's requested implicit-bias instruction was not prejudicial. Id.
In this case, unlike Plain , the district court did not conclude it lacked authority to give an implicit-bias instruction. Rather, it found that Instruction 5 adequately addressed the concern. Instruction 5 was based on the Iowa State Bar Association's latest version of Instruction 100.8. See Iowa State Bar Ass'n, Iowa Criminal Jury Instructions 100.8 (2018) (revised June 2016). The Iowa State Bar Association updated Instruction 100.8 in 2016 so that it now directs the jury to "avoid decisions based on generalizations, gut feelings, prejudices, sympathies, stereotypes, or biases." Id. This version of Instruction 100.8 did not exist at the time of Plain's trial and was not given in Plain . See Plain , 898 N.W.2d at 839 n.14 (Waterman, J., specially concurring) (quoting from the jury instructions). It is also noteworthy that both Williams and Fleming were of the same race, unlike in Plain where the defendant was African-American and the complaining witness was white. See id. at 809 (majority opinion). Given these factors, we find the district court did not abuse its discretion in declining to give Williams's requested implicit-bias instruction.6 This does not mean, of course, that it would have been an abuse of discretion to use Williams's requested instruction.
VII. Fleming's Convictions and Other Prior Bad Acts Not Known by Williams.
At trial, Williams asserted that he shot Fleming in self-defense. In support of this claim, Williams was allowed to introduce (1) evidence of Fleming's behavior on the day of the shooting, (2) any other specific acts by Fleming known to *634Williams, and (3) Fleming's alleged reputation for aggressive behavior. Specifically, Williams was permitted to introduce evidence that on the evening in question, Fleming was highly intoxicated, and that he had been acting tough, voicing threats, and driving recklessly. Williams also was allowed to offer proof that Fleming-a person who was short of stature-had a "Chihuahua complex."
However, Williams was not allowed to introduce Fleming's criminal history report7 or proof of specific prior acts of violence not known to Williams. Williams contends this was error. The State, meanwhile, responds that the district court's ruling can be sustained on several grounds. Among other things, the State urges us to clarify the meaning of Iowa Rule of Evidence 5.405.
Iowa Rule of Evidence 5.405, concerning "Methods of proving character," states,
a . By reputation or opinion. When evidence of a person's character or character trait is admissible, it may be proved by testimony about the person's reputation or by testimony in the form of an opinion. On cross-examination of the character witness, the court may allow an inquiry into relevant specific instances of the person's conduct.
b . By specific instances of conduct. When a person's character or character trait is an essential element of a charge, claim, or defense, the character or trait may also be proved by relevant specific instances of the person's conduct.
Before this rule was even adopted, we held in State v. Jacoby , "It is the rule in Iowa and the majority of jurisdictions that the quarrelsome, violent, aggressive or turbulent character of a homicide victim cannot be established by proof of specific acts." 260 N.W.2d 828, 838 (Iowa 1977).
As we explained in Jacoby ,
The reasons for the rule prohibiting proof of specific acts of violence appear to be at least threefold: (1) A single act may have been exceptional, unusual, and not characteristic and thus a specific act does not necessarily establish one's general character; (2) although the state is bound to foresee that the general character of the deceased may be put in issue, it cannot anticipate and prepare to rebut each and every specific act of violence; and (3) permitting proof of specific acts would multiply the issues, prolong the trial and confuse the jury.
Id. (quoting Henderson v. State , 234 Ga. 827, 218 S.E.2d 612, 615 (1975) ).
Then, after we had adopted rule 405 of the Iowa Rules of Evidence, which later became rule 5.405, we reaffirmed Jacoby . See Klaes v. Scholl , 375 N.W.2d 671, 675-76 (Iowa 1985). In Klaes , a citizen sued police officers for assaulting him. Id. at 672. The testimony was in conflict as to who was the aggressor. Id. at 673. We indicated that evidence of the citizen's "character for violence" would be admissible. Id. at 674. Quoting the rule 405, we said that "defendants could of course have introduced evidence of [the citizen's] violent character by reputation or opinion testimony." Id. at 675. Yet we held it was improper for the district court to have admitted specific instances of the citizen's prior conduct. Id. at 675-76. We rejected the notion that character is an essential element of a claim of self-defense, stating,
We believe, however, that in cases like this one the "issue" in question is not one of character but rather of conduct . We hold therefore the evidence of *635Scholl's prior conduct did not go to an essential element of self-defense as required by [ rule 5.405(b) ] and was not admissible.
Id. at 676 (citations omitted).
Three years later, however, we were confronted with the same issue in State v. Dunson , 433 N.W.2d 676, 677 (Iowa 1988), a criminal assault case where the defendant raised a claim of self-defense. The defendant sought to introduce evidence that shortly after the altercation in question, the alleged victim followed him and ran him over with her automobile. Id. at 679. We quoted rule 5.405(b) but did not address the distinction between conduct evidence and opinion or reputation evidence. Id. at 680-81. Nor did we comment on whether the victim's character for violence is an essential element of a self-defense claim. Id. We did not mention or even cite to Klaes . Id. Rather, we simply said that the evidence was "relevant" and "material" and therefore should have been admitted on that basis. Id.
In State v. Fish , the court noted that "most states with evidentiary rules similar to the Federal Rules of Evidence permit the defendant to introduce reputation and opinion evidence, but not specific acts of violence, to prove the victim's violent character." 222 Ariz. 109, 213 P.3d 258, 268 (Ariz. Ct. App. 2009). Citing Dunson , the Arizona court noted that Iowa was one of two states not to follow this approach, but it implicitly criticized Dunson for failing to discuss "the essential element issue." Id. at 269.
Uncertainty exists today as to the applicable rule in Iowa. The court of appeals decision in State v. Shearon , 449 N.W.2d 86 (Iowa Ct. App. 1989), illustrates this point. There the court of appeals said, "Specific instances of conduct may be used to demonstrate character when character is an essential element of a claimed defense." Id. at 87. Yet the court declined to take a position on whether character is an essential element of self-defense in a criminal case, stating,
This court notes that in the context of a civil case in which it was claimed that the combative character of an alleged assault victim should have been admitted, the Iowa Supreme Court held that specific instances of the victim's conduct did not go to an essential element of the defendant's claim of self-defense. Klaes v. Scholl , 375 N.W.2d 671, 676 (Iowa 1985). As the State has not made an analogous argument in this case, we assume the applicability of [ rule 5.405(b) ] and address our attention to whether Coaklay's testimony was relevant and/or prejudicial.
Id. at 87 n.1. Ultimately, it found the specific-act evidence inadmissible anyway because it "would have been substantially prejudicial and would have outweighed the probative value ...." Id. at 88.
Recently, in State v. Webster and State v. Einfeldt , we upheld on other grounds the exclusion of specific acts evidence that had been offered to prove a homicide victim's aggressive character. See State v. Webster , 865 N.W.2d 223, 243-44 (Iowa 2015) ; State v. Einfeldt , 914 N.W.2d 773, 783-84 (Iowa 2018). Yet we did say in Einfeldt , "[I]f the accused asserts he or she acted in self-defense, specific instances of the victim's conduct may be used to demonstrate his or her violent or turbulent character." 914 N.W.2d at 784. The State urges that this statement, which was not necessary to our decision, misstates the law.
We conclude today that the plain text of rule 5.405 should be followed. That text allows specific-acts evidence to be used to prove character only when character is an "essential element" of a charge, claim, or defense. Iowa R. Evid. 5.405(b ).
*636Character is not an essential element of justification. Iowa Code section 704.3 provided, "A person is justified in the use of reasonable force when the person reasonably believes that such force is necessary to defend oneself or another from any actual or imminent use of unlawful force." Depending on the facts and circumstances, a reasonable belief may exist-or may not exist-regardless of the other person's character.
Indeed, when Rule 5.405 was adopted, the Official Comment embraced Jacoby as "an example of Iowa application" of subsection (b ). Jacoby , as noted, does not allow specific acts to prove a victim's character. 260 N.W.2d at 838.
Furthermore, Dunson has come under criticism. Professor Laurie Doré has noted that Dunson did not overrule Klaes and is inconsistent with it. 7 Laurie Kratky Doré, Iowa Practice SeriesTM: Evidence § 5.405:2, at 324-25 (2017 ed.) [hereafter Doré]. In her view, Klaes is right:
[U]nless a defendant claims to have known about the victim's violent conduct (and therefore acted reasonably in using defensive force), a defendant seeking to admit evidence of a victim's character to support self-defense should only be permitted to use reputation or opinion evidence, not specific instances of the victim's conduct.
Id. at 325-26.
One of Professor Doré's former colleagues, Professor James Adams, has likewise criticized Dunson for "ignoring the analysis in Jacoby and Klaes " and giving "no effect" to the first part of rule 5.405. James A. Adams, Admissibility of Proof of an Assault Victim's Specific Instances of Conduct as an Essential Element of a Self-Defense Claim Under Iowa Rule of Evidence 405 , 39 Drake L. Rev. 401, 416-17 (1990). He goes on to say that "nothing in the Iowa Rules of Evidence or the Federal Rules of Evidence from which they were derived ... suggests such an interpretation [i.e., the interpretation in Dunson ] is appropriate or desirable." Id. at 429. Even if Dunson were correct, Professor Adams believes it would be subject to criticism for making a change in interpretation "without discussion of prior case law or any basis for the change." Id.
Thus, we hold that a defendant asserting self-defense or justification may not prove the victim's aggressive or violent character by specific conduct of the victim unless the conduct was previously known to the defendant. See Klaes , 375 N.W.2d at 676 ("[W]e are not dealing with the special situation in which the person claiming self-defense had actual knowledge of the other person's prior acts of violence."); Jacoby , 260 N.W.2d at 838-39 ("[A]ccording to most courts ... if, prior to the homicide, the defendant ... knew of other acts of violence of the deceased, he may, in support of his contention that he had reasonable grounds to believe himself in imminent danger from an assault by the deceased, introduce evidence of such prior unlawful acts of violence by the deceased." (alteration in original) (quoting 40 Am. Jur. 2d, Homicide , § 306, at 575) ); Doré, § 5.405:2, at 325 (distinguishing the situation where "a defendant claims to have known about the victim's violent conduct").
Our interpretation of rule 5.405 gives full effect to the rule. There are some cases where character is an essential element- Klaes gives alienation of affections and slander as examples. 375 N.W.2d at 676. Professor Doré notes, "In child custody situations ..., the character trait of moral unfitness may be an element and specific instances of conduct may be used to demonstrate that character trait." Doré, *637§ 5:405:2, at 526-27. But self-defense is not one of those situations.
Accordingly, we hold the district court did not err in ruling that Williams could not introduce Fleming's criminal record or other specific acts of violence not previously known to Williams.
VIII. Stand Your Ground Defense.
Lastly, Williams argues the district court erred when it held that amended Iowa Code section 704.1, which became effective on July 1, 2017, did not apply in his case. See 2017 Iowa Acts ch. 69, § 37 (codified at Iowa Code § 704.1 (2018)). During the 2017 session, the general assembly rewrote section 704.1 to read as follows:
1. "Reasonable force " means that force and no more which a reasonable person, in like circumstances, would judge to be necessary to prevent an injury or loss and can include deadly force if it is reasonable to believe that such force is necessary to avoid injury or risk to one's life or safety or the life or safety of another, or it is reasonable to believe that such force is necessary to resist a like force or threat.
2. A person may be wrong in the estimation of the danger or the force necessary to repel the danger as long as there is a reasonable basis for the belief of the person and the person acts reasonably in the response to that belief.
3. A person who is not engaged in illegal activity has no duty to retreat from any place where the person is lawfully present before using force as specified in this chapter.
Iowa Code § 704.1 (2018).
Most notable is subsection 3, a new stand your ground provision, which eliminates any duty to retreat before using force if one is not engaged in illegal activity. Id. The legislature provided that the 2017 amendment would not become effective until July 1, 2017-a few hours after Williams shot Fleming the evening of June 30. See 2017 Iowa Acts ch. 69, § 50; Iowa Code § 3.7(1) (2017).
We conclude the district court made the right call when it held the 2017 amendment did not apply in this case. The amendment was a change in substantive law, and it was the legislature's prerogative not to make that change effective until July 1.
Williams relies on Iowa Code section 4.13(2), which provides,
If the penalty, forfeiture, or punishment for any offense is reduced by a reenactment, revision, or amendment of a statute, the penalty, forfeiture, or punishment if not already imposed shall be imposed according to the statute as amended.
However, the 2017 amendment did not alter the punishment for murder; at most, it expanded the scope of a potential defense. See 2017 Iowa Acts ch. 69, § 37 (codified at Iowa Code § 704.1 (2018)).
Recently, in State v. Harrison , we held that the 2016 legislation dividing what had been second-degree robbery (a class "C" felony) into second-degree robbery and third-degree robbery (a class "C" felony and an aggravated misdemeanor) did not apply retroactively. 914 N.W.2d 178, 205 (Iowa 2018). We explained,
It is a well-settled law that substantive amendments to criminal statutes do not apply retroactively. Since third-degree robbery did not exist in the Iowa Code at the time of Harrison's offense, Harrison was not entitled to a jury instruction differentiating between felony robbery and misdemeanor robbery.
*638Id. (citations omitted). We think Harrison controls here.8
IX. Conclusion.
For the foregoing reasons, we conditionally affirm Williams's conviction and sentence, but we remand this case for further consideration of Williams's claim that his jury was not drawn from a fair cross section of the community in violation of the Sixth Amendment. If the court rejects that claim, then Williams's conviction and sentence shall stand. If the court accepts that claim, Williams shall receive a new trial.
AFFIRMED ON CONDITION AND REMANDED WITH DIRECTIONS.
Cady, C.J., and Wiggins and Appel, JJ., concur in divisions IV, VII, and VIII of the court's opinion but dissent as to divisions V and VI.
Waterman, Christensen, and McDonald, JJ., concur in divisions V, VI, VII, and VIII of the court's opinion but dissent as to division IV.