State v. Oatney

No. 866 September 16, 2026 1 IN THE COURT OF APPEALS OF THE STATE OF OREGON STATE OF OREGON, Plaintiff-Respondent, v. BILLY LEE OATNEY, JR., Defendant-Appellant. Washington County Circuit Court 18CR70058; A181144 Beth L. Roberts, Judge. Argued and submitted December 5, 2025. Richard L. Wolf argued the cause and filed the briefs for appellant. Also on the opening brief was Richard L. Wolf, P.C. Timothy A. Sylwester, Assistant Attorney General, argued the cause for respondent. Also on the brief were Dan Rayfield, Attorney General, Benjamin Gutman, Solicitor General, and Leigh A. Salmon, Assistant Attorney General’ Before Tookey, Presiding Judge, Kamins, Judge, and Jacquot, Judge. KAMINS, J. Reversed and remanded. 2 State v. Oatney Cite as 353 Or App 1 (2026) 3 KAMINS, J. Defendant appeals from a judgment of conviction for first-degree murder on retrial following the grant of post-conviction relief. He raises seven assignments of error concerning trial proceedings and his immunity agreement with the state. We reverse and remand based on the third and fourth assignments of error and therefore address those assignments first. We then address defendant’s sec- ond and seventh assignments of error, as they may arise on remand. Because defendant’s first, fifth, and sixth assign- ments of error are unlikely to recur on remand, we do not address them.1 State v. James, 350 Or App 71, 84, ___ P3d ___ (2026). We take the historical facts from the Supreme Court’s decision in an interlocutory appeal in this case, State v. Oatney, 369 Or 555, 558, 508 P3d 482 (2022) (Oatney IV), and our decision from the post-conviction appeal, Oatney v. Premo, 275 Or App 185, 219, 369 P3d 387, rev den, 359 Or 847 (2015) (Oatney II). In 1996, the victim, S, was mur- dered. Defendant entered into an immunity agreement with the state, in which the state—presumably under the theory that defendant was not the murderer—promised him use and derivative use immunity2 in exchange for his account of 1 In defendant’s first assignment of error, he contends that the trial court erred by denying his motion to disqualify the judge assigned to his case, pursu- ant to ORS 14.250 to 14.270. Because that judge is retired, that ruling is unlikely to recur on remand. See State v. Baughman, 164 Or App 715, 723, 995 P2d 551 (2000), rev dismissed as improvidently allowed, 333 Or 596 (2002) (not addressing assignment of error where “ruling arose in a particular context that is unlikely to recur on remand). In defendant’s fifth assignment of error, he argues that the trial court erred by denying a mistrial based on the prosecutor’s statements in closing argument that defendant’s argument included “lies” and “was the kind of dishonesty that [the jury] heard in this case.” Although those statements are improper, there is no reason to think they will occur on remand. See James, 350 Or App at 84 (not addressing prosecutor’s improper closing argument when reversing on other grounds because “they ought to be avoided or preserved should they occur on remand”). In defendant’s sixth assignment of error, he contends that the trial court erred in denying a motion for a mistrial after the prosecution committed a Brady violation by failing to disclose that a witness was recently shown photographs that that witness used to identify defendant during the orig- inal investigation. Because defendant is now aware of the undisclosed evidence, any error is unlikely to recur on remand. 2 When a witness is granted use and derivative use immunity, “the witness is not immune from prosecution, but the state may not use the immunized testi- mony or any of its direct or indirect fruits.” State v. Soriano, 68 Or App 642, 644 4 State v. Oatney events. Oatney II, 275 Or App at 209. In his immunized state- ment, defendant indicated that his codefendant Johnston had murdered the victim and that defendant’s role was limited to helping Johnston dispose of the victim’s clothing along with the items stolen from her apartment. Oatney IV, 369 Or at 559. At the detectives’ request, defendant gave them permis- sion to play a recording of his statement for Johnston, who had refused to speak to police about the murder up to that point. Id. After hearing defendant’s statement that Johnston committed the crime alone, “Johnston’s face turned beet red, and he clenched and shook his fists.” Id. (internal quotation marks omitted). He immediately countered that defendant was the murderer and asserted in later interviews that he and defendant had committed the crime together. Id. Both Johnston and defendant were charged with the aggravated murder of S. Johnston pleaded guilty, and the state agreed not to seek the death penalty in exchange for his testimony at defendant’s trial. Id. at 558. At defendant’s first trial, Johnston repeated his account, which resulted in defendant’s conviction. Id. That conviction was overturned after a post- conviction relief proceeding during which the court deter- mined that the state had violated defendant’s use and deriv- ative use agreement by introducing Johnston’s statements and testimony. Id. at 558, 560-61. In the following retrial, Johnston did not testify, and defendant was again convicted of first-degree murder. Defendant appeals that judgment. I. THIRD AND FOURTH ASSIGNMENTS OF ERROR In defendant’s third assignment of error, he con- tends that the trial court erred by ruling that Johnston’s conviction was derived from defendant’s immunized state- ment and that, if defendant sought to admit the convic- tion, it would “open the door and allow the State to call Mr. Johnston to explain that conviction.” We review the admission of evidence where there is only one legally correct outcome for legal error. State v. Titus, 328 Or 475, 481-82, 982 P2d 1133 (1999). n 3, 684 P2d 1220 (1984). In defendant’s agreement, the state promised defendant that “anything you say during the course of this interview and any information that we derive from what you tell us cannot ever be used against you.” Oatney II, 275 Or App at 204 (internal quotation marks omitted). Cite as 353 Or App 1 (2026) 5 A. Johnston’s Conviction as Derivative Evidence Generally, to demonstrate that evidence is derived from an immunized statement, a defendant must prove that their statement or testimony was made subject to the state’s promise of immunity. The state then must show that its evidence “is derived from a legitimate source wholly inde- pendent” of the immunized statement. Kastigar v. United States, 406 US 441, 460, 92 S Ct 1653, 32 L Ed 2d 212 (1972). Usually, the trial court holds a hearing—referred to as a “Kastigar hearing”—in which the state must prove that all evidence it proposes to use at trial is wholly independent of the defendant’s immunized statement. Oatney IV, 369 Or at 562. If evidence is not derived from an independent source, it is considered derivative evidence, meaning that it was “obtained by use—evidentiary or nonevidentiary—of the immunized statement.” Oatney II, 275 Or App at 210. As no party argues to the contrary, we assume with- out deciding that a conviction can be derived from an immu- nized statement. As such, the initial question is whether Johnston’s conviction was derived from defendant’s immu- nized statement or an independent source. If the convic- tion is not derived from defendant’s immunized statement, then its admission is unrelated to the immunity agreement and cannot open the door to evidence that is subject to the immunity agreement. See Oatney IV, 369 Or at 570 (deter- mining that arguments based on “admissible, nonderiva- tive evidence” would not open the door to Johnston’s tes- timony). To be from an independent source, the evidence must have developed independently, such that the steps taken to obtain the evidence are untainted by defendant’s immunized statement. Where the causal chain is tainted by defendant’s immunized statement, that evidence is derived from it. See Oatney II, 275 Or App at 219-21 (determining that the evidence was not derived from an independent source where the state could not show that, without defen- dant’s immunized statement, Johnston would have made the same decision to testify); see also U.S. v. Schmidgall, 25 F3d 1523, 1528, reh’g den, 37 F3d 639 (11th Cir 1994) (“To establish a wholly independent source, the government must demonstrate that each step of the investigative chain 6 State v. Oatney through which the evidence was obtained is untainted.” (Internal quotation marks omitted.)). Therefore, we con- sider the causal chain that led to Johnston’s conviction to determine if the conviction was derived from defendant’s immunized statement. Johnston’s conviction stemmed from a guilty plea. See Blain v. Cain, 327 Or App 584, 590, 536 P3d 623 (2023) (“[I]n pleading guilty, a defendant admits that they com- mitted the past acts charged in the indictment, and that admission forms the basis for determining their guilt.”). That plea agreement was obtained after reading defendant’s immunized statement to Johnston and was predicated on Johnston’s agreement to testify against defendant, testi- mony that echoed the account Johnston gave in response to hearing defendant’s immunized statement. Oatney II, 275 Or App at 219. As we have already determined, that testimony was derived from defendant’s immunized statement. Id. It follows that because Johnston’s plea agreement formed the basis of his conviction, and that plea agreement was made in exchange for his derivative testimony, his conviction is also derived from defendant’s immunized statement.3 There is no way to determine whether the government would have made the same plea offer or whether Johnston would have accepted the same plea agreement without the motivating factor of defendant’s immunized statement, and therefore, the conviction is derived from it. B. “Opening the Door” in an Immunity Context As Johnston’s conviction is derived from defendant’s immunized statement, we next consider whether defendant’s introduction of that derivative evidence (Johnston’s convic- tion) would open the door and allow the state to introduce 3 Defendant contends that Johnston’s conviction is not derived from his immunized statement, because if it were, Johnston’s conviction could be over- turned based on violations of defendant’s immunity agreement. However, defen- dant’s immunity agreement was a waiver of defendant’s rights against self- incrimination. The right against self-incrimination under the Fifth Amendment and Article I, section 12, of the Oregon Constitution is a personal right, and therefore, the violation of defendant’s immunity agreement cannot be asserted by another individual. Dept. of Human Services v. F. T. R., 306 Or App 697, 703, 475 P3d 931 (2020); see State v. Makuch/L. A. R., 340 Or 658, 671, 136 P3d 35 (2006) (evidence may be suppressed due to the violation of a personal right only if the person seeking suppression’s rights were violated). Cite as 353 Or App 1 (2026) 7 additional derivative evidence (Johnston’s testimony).4 The trial court determined that, because Johnston’s conviction was derived from defendant’s immunized statement and supported a conclusion that Johnston murdered S, defen- dant introducing the conviction would open the door to the state calling Johnston to explain the conviction. In its writ- ten order, the trial court determined: “Defendant may not present any evidence derived from Defendant’s October 23, 1996, immunized statement or evidence derived from that statement that suggests Willford Johnston committed the murder of [S] without opening the door to the state calling Willford Johnston in this present case.” “Open the door” is an “inherently vague” phrase, and we look to context to determine what a trial court meant by using it. State v. Gutierrez, 304 Or App 431, 439, 466 P3d 75 (2020). Here, the trial court relied on the state’s argument that defendant’s introduction of the derivative evidence of Johnston’s conviction would “invite further inquiry” into the nature of the conviction, and therefore, it would allow the state to introduce Johnston’s testimony. See State v. Miranda, 309 Or 121, 129, 786 P2d 155 (1990) (“affirmatively” introducing suppressed evidence “invited further inquiry” by the state into the suppressed evidence). Because defendant’s immunity stems from an infor- mal immunity agreement, it is governed by contract princi- ples. See Oatney II, 275 Or App at 204 (“When a person inde- pendently enters into an agreement with a prosecutor to provide information in exchange for some type of immunity, the resulting informal immunity agreement is governed by contract principles.”). Contract principles provide for situations of a “contract omission”—where a contract does not address a reasonably foreseeable contingency. State v. King, 361 Or 646, 658, 398 P3d 336 (2017). That issue arises 4 The state additionally argues that defendant’s introduction of Johnston’s conviction could create an independent motivation for Johnston to testify such that the testimony would no longer be derived from defendant’s immunized state- ment. As the court identified in Oatney IV, whether intervening events could create an independent motivation for Johnston to testify is something the state was free to argue before the trial court, regardless of whether defendant intro- duced derivative evidence. Oatney IV, 369 Or 576-77. Because the state did not attempt to introduce such evidence of an independent motivation, we are unable to address that argument. 8 State v. Oatney here, as defendant’s agreement does not address whether the state has a remedy if defendant introduces derivative evidence. When a contract omits a term that is essential to determining the parties’ rights and obligations, such as out- lining the state’s options when defendant introduces deriv- ative evidence, courts may supply a default rule or implied term. King, 361 Or at 658-59. Common practice may sup- port imposing a default rule allowing the state to respond to defendant’s introduction of evidence. See Miranda, 309 Or at 128 (“A defendant’s own inquiry on direct examination into the contents of otherwise inadmissible statements opens the door to further inquiry on cross-examination relating to those same statements.”). However, a contract concerning the waiver of a criminal defendant’s rights requires special consideration of due process in addition to usual considerations of com- mon practice and “basic principles of justice.” King, 361 Or at 660, 667; see U.S. v. Alemann, 286 F3d 86, 90 (2d Cir 2002), cert den, 552 US 1187 (2008) (“[d]ue process concerns color our interpretation of a contract involving [a] defen- dant’s constitutional rights” like an immunity agreement); Dorsciak v. Gladden, 246 Or 233, 243-45, 425 P2d 177 (1967) (due process requires knowing and voluntary waiver of right against self-incrimination). Consideration of defendant’s due process rights and the state’s superior bargaining posi- tion require that such an expansive waiver cannot be read into defendant’s immunity agreement. See King, 361 Or at 660 (noting a court may place “the burden of expression on the party that can better cope with it because of bargaining power and drafting skill” (internal quotation marks omit- ted)); cf. State v. Lobue, 300 Or App 340, 348 n 1, 453 P3d 929 (2019) (Lagesen, P. J., concurring) (acknowledging “the generally recognized principle that, in the criminal context, agreements with the government should be strictly con- strued against the government, given its superior bargain- ing power and potential due process concerns”). Further, the state’s promise of immunity was the only consideration it offered in exchange for defendant’s waiver of constitutional rights, and that consideration induced defendant’s waiver. Cf. Santobello v. New York, 404 US 257, 261-64, 92 S Ct 495, 30 L Ed 2d 427 (1971) (discussing that a prosecutor’s promise Cite as 353 Or App 1 (2026) 9 in a plea agreement “can be said to be part of the induce- ment or consideration” for the waiver of defendant’s rights including the right to remain silent, and as such, the “prom- ise must be fulfilled”). Reading the agreement to allow the state to breach even when defendant did not would affront the voluntariness of that waiver. See Oatney IV, 369 Or at 570 (“[A]ny potential prejudice to the state is a result of the state’s initial decision to grant defendant use and deriva- tive use immunity. Having made that decision, it would not be appropriate to permit the state to effectively breach the agreement * * *.”); cf. U.S. v. Jimenez-Bencevi, 788 F3d 7, 16-17 (1st Cir 2015) (court violated defendant’s immunity agreement and due process right by requiring disclosure of his immunized statement to a witness where the immunity agreement did not allow for the possibility of opening the door through the presentation of evidence). That is not to say there are no limits on what a defendant may introduce without the state being allowed to respond. “[I]mmunity from use and derivative use leaves the witness and the * * * [g]overnment in substantially the same position as if the witness had claimed his privilege in the absence of a grant of immunity.” Kastigar, 406 US at 458-59 (emphasis added) (internal quotation marks omit- ted). To allow defendant to create a fundamentally mislead- ing impression on a significant issue using evidence derived from the immunized statement would leave the state in a substantially worse position than if defendant had remained silent. If defendant were to use Johnston’s conviction to argue that Johnston alone murdered S, contradicting the factual basis of Johnston’s plea (that he and defendant mur- dered S together), that would create such a fundamentally misleading impression on a significant issue as to make it truly necessary for the court to open the door to allow the state to correct that misleading impression. State v. Craine, 271 Or App 101, 111, 349 P3d 628 (2015); see Morris v. State of Oregon, 345 Or App 161, 582 P3d 190 (2025), rev den, 375 Or 67 (2026) (Hellman, J., concurring) (noting defense coun- sel must abide by their “duty of candor to the court and can- not advance legal or factual positions they know to be false” citing the Rules of Professional Conduct). A clear connection between defendant’s derivative evidence, the misleading 10 State v. Oatney impression on a significant issue, and how the state’s evi- dence will rebut that misleading impression is necessary to ensure that both defendant and the state are left in “sub- stantially the same position” as if defendant had not made the immunized statement in the first place. Kastigar, 406 US at 458; cf. State v. Johnson, 342 Or 596, 622, 157 P3d 198 (2007), cert den, 552 US 1113 (2008) (the defendant’s introduction of suppressed evidence opened the door where that evidence aligned with the defendant’s current theory of the case based on a false inference, clearly creating a mis- leading impression). Here, it was not clear that the introduc- tion of Johnston’s conviction would create such a misleading impression without further argument from defendant. The court’s ruling that any evidence, including the conviction, that “suggests Willford Johnston committed the murder of [S]” would open the door to Johnston’s testimony was overly broad. That ruling presumed that such evidence would create a misleading impression without argument from defendant to support that presumption. Such a misleading impression must be likely rather than merely possible to justify allow- ing the state to breach its agreement. As defendant argued before the trial court, evidence that Johnston was convicted of S’s murder does not create a misleading impression that he murdered S without defendant. Therefore, the trial court erred. C. Fourth Assignment of Error: Denial of Motion for Mistrial Based on State’s Improper Argument In defendant’s fourth assignment of error, he argues that the trial court erred by denying his motion for a mis- trial after the state suggested in closing that Johnston was not involved in S’s murder. We review the denial of a motion for mistrial for abuse of discretion. State v. Smith, 310 Or 1, 24, 791 P2d 836 (1990); State v. Serrano, 355 Or 172, 197, 324 P3d 1274 (2014), cert den, 576 US 1037 (2015). The trial court’s denial constitutes an abuse of discretion if the pros- ecutor’s remarks denied a defendant a fair trial. Smith, 310 Or at 24. In closing argument and rebuttal, the state responded to defendant’s arguments that Johnston had murdered S by suggesting to the jury—despite Johnston’s Cite as 353 Or App 1 (2026) 11 conviction for the crime—that Johnston was not involved.5 Defendant contends that those comments were improper, and the court erred by denying a motion for mistrial.6 A prosecutor’s false or misleading argument vio- lates due process if it rises to the level of denying defendant a fair trial. See State v. Pouncey, 303 Or App 365, 369, 464 P3d 448, rev den, 367 Or 76 (2020) (“[W]e review the trial court’s denial of [the] defendant’s mistrial motion for an abuse of discretion, asking whether the prosecutor’s unrem- edied misstatement so affected the jury’s consideration as to deny [the] defendant a fair trial.”); see Andrew v. White, 604 US 86, 93, 145 S Ct 75, 220 L Ed 2d 340 (2025) (“[P] rosecutors’ prejudicial or misleading statements violate due process if they render a trial * * * fundamentally unfair.”). Prosecutors bear “special ethical considerations,” including an obligation not to present an argument when “the prosecutor knows an inference to be false.” See State v. Strain, 374 Or 783, 791 n 5, 583 P3d 1002 (2026) (listing examples of special ethical considerations for prosecutors from Standard 3-6.8 of the ABA Criminal Justice Standards for the Prosecution Function (2017)). Where the state invites the jury to draw an inference that it knows to be false, a defendant is denied a fair trial, regardless of whether the evidence before the jury proves it to be false. See State v. Burton, 373 Or 750, 758, 767 n 9, 571 P3d 736 (2025) (noting other courts have relied on the special obligation of prose- cutors not to makes false arguments in acknowledging that “ ‘it is decidedly improper for the government to propound inferences that it knows to be false, or has very strong 5 The state described Johnston’s “noninvolvement”: “This defendant, and this defendant alone, based on the evidence that you’ve heard, is entirely responsible for murdering [S] under the circumstances that are outlined here * * * * * there’s no evidence at all, again, that Willford Johnston was involved in this.” 6 Before the trial court, defendant argued that the statements amounted to a due process violation. On appeal, defendant argues the statements were a Napue violation. Napue v. Illinois, 360 US 264, 269, 79 S Ct 1173, 3 L Ed 2d 1217 (1959). However, Napue requires the state not to use false evidence rather than make false arguments, as occurred here. See Tiner v. Premo, 284 Or App 59, 78, 391 P3d 816, rev den, 361 Or 886 (2017) (prosecutor did not commit a Napue violation by making an improper closing argument because “statements an attorney makes during closing argument are not evidence”). 12 State v. Oatney reason to doubt’ ” (quoting United States v. Blueford, 312 F3d 962, 968 (9th Cir 2002))). Because a prosecutor’s client is the public, they have “a heightened duty of candor to the courts” and should not make statements that they do “not reason- ably believe to be true.” Standard 3-1.4 of the ABA Criminal Justice Standards for the Prosecution Function (2021). By emphasizing “the noninvolvement” of Johnston, the state improperly invited the jury to draw an inference it knew to be false—that Johnston was not involved in S’s death. The state now contends that its argument regard- ing Johnston’s “noninvolvement” and that “this defendant, and this defendant alone, based on the evidence that you’ve heard, is entirely responsible for murdering [S]” did not mis- represent the evidence actually presented and complied with the requirement that “counsel may not suggest that they are aware of evidence that was not presented to the jury.” Burton, 373 Or at 761-62. That may be true, but the state strayed too far in the opposite direction—presenting arguments antithetical to evidence of which the state was aware and that was not presented to the jury. The state argues that it was only responding to defendant’s argument that “Johnston may have murdered the victim while acting alone.” However, regardless of the motivation, the prosecutor’s argument that “this defendant alone” murdered S, immediately prior to stating that “there’s no evidence at all, again, that Willford Johnston was involved in this” was plainly contrary to what the prosecutor knew to be true. See Blueford, 312 F3d at 968 (determining the defendant was denied a fair trial where the prosecutor’s arguments asked the jury to infer facts the pros- ecutor knew to be false because the prosecutor had specific evidence contradicting the inference that was not introduced at trial). That argument denied defendant a fair trial, and therefore, it was an abuse of discretion not to grant defen- dant’s motion for a mistrial. Because defendant’s second and seventh assign- ments of error may recur on remand, we address them below. II. SECOND ASSIGNMENT OF ERROR Defendant contends that the prosecutor and trial court violated his immunity agreement in multiple ways. Cite as 353 Or App 1 (2026) 13 Defendant’s “informal immunity agreement is governed by contract principles.” Oatney II, 275 Or App at 204; United States v. Plummer, 941 F2d 799, 803 (9th Cir 1991). Therefore, we review the court’s factual findings for any evidence, and we review whether the facts establish a violation of the immunity agreement for legal error. Plummer, 941 F2d at 803; Santoro v. Eagle Crest Estate Homesite Owners Assn., 319 Or App 793, 798, 512 P3d 828 (2022); Dept. of Education v. Vantage, 243 Or App 557, 566, 261 P3d 17 (2011). A. Buden Shifting Regarding Immunity Agreement Violation Defendant first argues that the trial court erred by requiring him to prove breach of the immunity agreement before requiring the state to prove that its evidence was not derived from the immunized statement—the showing required under Kastigar. In Kastigar, the court considered whether the government may compel testimony, subject to a grant of immunity, from a witness who invoked their right against self-incrimination. The court held that, once a person has demonstrated that they spoke subject to a state grant of immunity, the state must meet the “heavy burden” of prov- ing that any evidence it proposes to use to prosecute them is “derived from legitimate independent sources.” Kastigar, 406 US at 461-62. Defendant argues that the state must meet that burden here. Unlike the defendant in Kastigar, defendant here voluntarily waived his rights against self-incrimination through his informal immunity agreement. Because his waiver was voluntary rather than compelled, we look to the terms of the parties’ agreement to determine its scope. An informal immunity agreement, like defen- dant’s, is governed by contract principles. Oatney II, 275 Or at 204. Under contract law, a party must prove breach by a preponderance of the evidence in order to recover for a breach of contract claim. Northwest Natural Gas Co. v. Chase Gardens, Inc., 333 Or 304, 312 n 3, 39 P3d 846 (2002); Currey v. Butcher, 37 Or 380, 390, 61 P 631 (1900). Applying that principle in this case, defendant would bear the burden 14 State v. Oatney of proving that the state’s evidence breached the agreement by preponderance of the evidence prior to the court requir- ing the state to demonstrate that its evidence was derived from an independent source. Defendant contends that the prior appeals of this case suggested that he need not prove breach before the state is required to demonstrate an independent source. However, the prior cases focused solely on issues concerning the state’s burden. Oatney II, 275 Or at 217 (“If trial counsel had raised [the issue of Johnston’s testimony being derived from defen- dant’s immunized statement], the state would have had the burden of showing that Johnston’s statements and testimony were derived from a legitimate source * * *.” (Internal quota- tion marks omitted.)); Oatney IV, 369 Or at 573-74 (explain- ing how Kastigar burden applies to witness testimony). As such, they do not examine whether defendant was required to first prove breach before applying that burden. Typically, we “look to Kastigar and its progeny in understanding use and derivative use immunity in the context of this particular case.” Oatney IV, 369 Or at 573. Other courts applying Kastigar to informal immunity agreements have required a defendant to demonstrate a breach. Specifically, before requiring the government to meet its burden, “[a]s in any contract case, [the defendant] must show that the contract was breached by a preponder- ance of the evidence.” U.S. v. Mendoza, 78 F3d 460, 464-65 (9th Cir 1996); see U.S. v. Hemphill, 514 F3d 1350, 1354 (DC Cir 2008) (“the defendant has the burden to prove any gov- ernment breach” of an informal immunity agreement, and what is considered a breach is determined by the terms of the agreement).7 Here, because the agreement requires the 7 Several other courts have assumed Kastigar applied without considering whether the nature of the agreement required a defendant to meet an additional burden. See U.S. v. Palumbo, 897 F2d 245, 249 (7th Cir 1990) (determining that because the parties did not dispute that the defendant had received informal use and derivative use immunity, Kastigar was triggered and the government bore the burden of proving all evidence it proposed to use was derived from legitimate independent sources including evidence used to obtain the indictment); United States v. Williams, 809 F2d 1072, 1083 (5th Cir 1987) (explaining that because the defendant cooperated with the government under an immunity agreement and was indicted on charges related to that investigation, the government bore the burden of proving an independent source for all evidence introduced). Cite as 353 Or App 1 (2026) 15 state to provide use and derivative use immunity, defendant proves breach by showing that the state made use or deriv- ative use of his immunized statement. Based on contract principles, our prior consider- ation of the case, and Kastigar and its progeny, the court did not err in placing the burden on defendant to demonstrate a breach prior to shifting the burden to the state. B. Prosecutors, Witnesses, and Evidence in Closing Statement Not Derived from Defendant’s Statement Defendant next contends that the trial court erred in allowing prosecutors and witnesses who were exposed to the immunized testimony to work on the case, to present the case to a grand jury, and to testify at trial.8 Defendant also argues that derivative evidence was used during closing argument. Whether facts establish a violation of an immu- nity agreement is a question of law. Plummer, 941 F2d at 802. 1. Prosecutors Defendant contends that the prosecutors’ exposure to both the immunized statement and derivative informa- tion tainted their preparation of the case and violated defen- dant’s immunity agreement. Specifically, defendant argues that prosecutors are prohibited from using immunized statements in any prosecutorial decision-making and that safeguards like a filter or taint team to protect against uses of immunized and derivative information were necessary to prevent that type of violation of the immunity agreement. A prosecutor’s exposure to an immunized statement can influence prosecutorial decision-making short of intro- ducing tainted evidence. State v. Soriano, 68 Or App 642, 663, 684 P2d 1220 (1984). For example, exposure can impact a prosecutor’s decision on whether to pursue a line of inves- tigation, whether to prosecute at all, or whether to offer a plea bargain. It can also illuminate the significance of other 8 The trial court required defendant to prove breach by a preponderance of the evidence in considering the admissibility of the evidence related to the grand jury proceeding and subsequent Kastigar hearing. 16 State v. Oatney evidence or impact trial strategy. Id. The state’s promise protects against such uses. Thus, it requires that the state’s pre-trial and trial strategy and the scope of its investigation be based on independent sources. See U. S. v. Danielson, 325 F3d 1054, 1074 (9th Cir 2003) (requiring the government to prove its trial strategy was derived from legitimate indepen- dent sources to meet its burden under Kastigar for use and derivative use immunity); cf. Oatney II, 275 Or App at 209 (evidence derived from the immunized statement includes “any evidence obtained by use—evidentiary or noneviden- tiary—of the immunized statement”). Therefore, we agree with defendant that prosecu- tors are prohibited from using immunized statements in prosecutorial decision-making. However, addressing that taint does not necessarily require, as defendant posits, a taint team or that a prosecutor have no knowledge of the immunized statement. Instead, the prosecution must prove that “its proposed evidence is without taint” and that “its case is unaffected by prohibited non-evidentiary uses.” Soriano, 68 Or App at 664; Oatney II, 275 Or App at 209. That burden may be “virtually undischargeable” in some cases, United States v. McDaniel, 482 F2d 305, 312 (8th Cir 1973), but here, the state successfully discharged it. The trial court evaluated the prosecutorial decision- making, requiring the state to prove that it had “ indepen- dent leads in which to prosecute” and that it had not “used that testimony against defendant.” Applying that standard, and relying on the declarations of the two prosecutors, the court determined that “[a]s a question of fact, I think for the Court to decide and given the facts, I’m not finding that there’s a need to remove this team from the prosecution at this time,” concluding that defendant had not met his bur- den to prove breach. The record supports the trial court’s factual find- ing that the prosecutors had independent leads. One pros- ecutor declared that he reviewed defendant’s immunized statement “in order to make certain that the tainted infor- mation or information derived from the tainted information was not used [before the] grand jury and will not be used in trial” and had developed his conclusions about trial strategy Cite as 353 Or App 1 (2026) 17 based on “early police reports leading up to the immunized statement.” The other prosecutor averred that he had read summaries of defendant and Johnston’s statements and the Oatney II opinion but had otherwise “chosen not to learn the details of defendant’s immunized statement.” That min- imal exposure, or exposure in order to ensure derivative evidence is not used, does not violate defendant’s immunity agreement. 2. Witnesses Defendant also challenges the admission of testi- mony by Travis Hampton, one of two original lead detec- tives, and Kevin Winfield, an investigator during the original trial and retrial, arguing that their exposure to defendant’s statement tainted their testimony before the grand jury and indicated that they made non-evidentiary use of defendant’s statement during their investigation, including using derived evidence while interviewing other witnesses. Defendant also argues that the admission of tes- timony by Josh Galbraith, a former neighbor of defendant, violated defendant’s immunity agreement because that wit- ness came forward after defendant’s arrest (which itself was based on Johnston’s statement). We defer to the trial court’s credibility finding and are bound by the trial court’s factual findings if there is evidence in the record to support them. A. J. T. v. Croft, 311 Or App 574, 577, 492 P3d 778 (2021) (“[W]e generally defer to the trial court for its assessment of credibility.”). In immunity cases, a credibility finding includes both a witness’s truthfulness and whether a witness “is truly able to isolate” the factors that led to his testimony and investigative path. Oatney IV, 369 Or at 575. Whether the facts establish a violation of an immunity agreement is a question of law, which we review for legal error. Plummer, 941 F2d at 802; Santoro, 319 Or App at 798. Generally, if a witness is exposed to immunized information, a witness’s testimony must be excluded if the immunized statement shaped, altered, or affected the infor- mation provided, even if the witness is testifying from per- sonal knowledge. Oatney IV, 369 Or at 574. “Generalized denials that the exposure shaped, altered or affected the 18 State v. Oatney content of a witness’s subsequent testimony are insufficient.” Id. at 575. Hampton had a police report summarizing the immunized statement and the immunized statement itself in a binder before him both when he testified before the grand jury and when he testified during the Kastigar hearing. While he did not refer to the binder during his grand jury testimony, he did use documents in the binder “to refresh [his] memory” during the Kastigar hearing. Defendant argues that that use of the immunized statement is prohibited. See Aiken v. U.S., 956 A2d 33, 45 (DC 2008) (Aiken I) (“[A] prohibited use occurs if a witness’s recollec- tion is refreshed by exposure to the defendant’s immunized testimony * * *.” (Internal quotation marks and citations omitted.)). Defendant also contends that the admission of Winfield’s testimony violated defendant’s immunity agree- ment, due to Winfield’s exposure to defendant and Johnston’s statement shaping his investigation and his opinion that S was raped. The trial court credited Hampton and Winfield’s testimony that the investigation did not rely on anything derived from defendant’s statement and that the evidence presented to the grand jury “was not tainted by the immu- nized statement of [defendant].” Those findings are sup- ported by the record. The immunized statement’s availability to a wit- ness during his grand jury testimony to refresh a witness as to its contents is not the equivalent of the witness using it to refresh his recollection as to the investigation during the grand jury proceeding. Nor is using it to refresh his memory during a subsequent Kastigar hearing the equiv- alent of using it to refresh h