When Must a Military Judge Instruct on an Affirmative Defense? Lessons from United States v. Castillo

Published by Cave & Freeburg LLP | Military Justice Defense Attorneys

Case Citation: United States v. Castillo, No. ACM 40705 (A.F. Ct. Crim. App. Mar. 11, 2026) | Unpublished

A recent Air Force Court of Criminal Appeals decision — United States v. Castillo — raises an important question every military defense lawyer must understand: when does a military judge have a duty to instruct on an affirmative defense, even during a guilty plea proceeding? The answer directly affects court-martial strategy, plea negotiations, and appellate rights for servicemembers facing charges under the Uniform Code of Military Justice (UCMJ).

At Cave & Freeburg LLP, we defend servicemembers at courts-martial and on appeal across all branches of the military. This case illustrates how the failure to raise — or the deliberate waiver of — an affirmative defense instruction can determine the outcome of an appeal.

What Happened in United States v. Castillo?

Technical Sergeant Christian Castillo pleaded guilty at a general court-martial at Scott Air Force Base, Illinois, to one specification of abusive sexual contact under Article 120, UCMJ. The conviction rested on a single incident in which Castillo sexually touched his wife while she was asleep, between November 2017 and April 2018. He admitted he knew she was asleep, that she had given no prior consent, and that he understood his conduct was wrong.

The military judge sentenced Castillo to a bad-conduct discharge, four months of confinement, and a reduction to E-1. The convening authority suspended the reduction in rank and waived forfeitures for six months to benefit Castillo’s dependents, consistent with the plea agreement.

On appeal, Castillo argued three issues: first, that factual inconsistencies in the record — and the military judge’s failure to instruct him on the mistake of fact defense — made his guilty plea improvident; second, that the bad-conduct discharge was too severe; and third, that excessive post-trial delay violated his due process rights. The court rejected all three arguments and affirmed the findings and sentence.

The Central Legal Issue: When Does a Military Judge Have to Instruct on Mistake of Fact?

The most significant legal issue in Castillo involves the defense of mistake of fact — specifically, mistake of fact as to whether the victim was asleep and therefore unable to consent. This is the same affirmative defense framework that courts apply whenever some evidence in the record suggests the accused may have had a good-faith, reasonable belief negating an element of the charged offense.

The rule: if any evidence raises a plausible affirmative defense — through testimony, documentary evidence, or the record as a whole — the military judge must either instruct the panel (or himself, in a bench trial) on that defense, or resolve why no instruction is required.

In Castillo, the defense had filed a Military Rule of Evidence 412 motion before trial. That motion sought to admit evidence of the couple’s prior sexual history, which arguably could have supported a mistake of fact defense — either by suggesting Castillo reasonably believed he had consent, or by creating doubt about whether he actually knew his wife was asleep. The military judge explained precisely how that evidence could have operated:

“Evidence could very well be relevant to show consent, which would therefore tend to butt up against or contradict the Government’s burden beyond a reasonable doubt to show that the victim was asleep and unable to consent. Or the evidence could have done the same, essentially, attacked the Government’s burden to show that the accused knew or reasonably should have known that [the victim] was asleep and unable to consent.”

In other words, the military judge herself recognized that sufficient evidence could have triggered a mistake-of-fact instruction. The critical distinction in Castillo: Castillo waived the MRE 412 motion. He chose not to introduce that evidence. Once he waived it, no inconsistent matter remained in the record to trigger the judge’s duty to instruct.

The Guilty Plea Framework: What Courts Look for on Appeal

When an accused pleads guilty, the military judge conducts a thorough providence inquiry under United States v. Care, 40 C.M.R. 247 (C.M.A. 1969). This inquiry requires the judge to ensure the accused understands the law in relation to the facts, and that no matter inconsistent with the plea exists in the record.

The Air Force Court of Criminal Appeals applies the substantial basis test on appeal: it will not reject a guilty plea unless it finds something in the record — regarding the factual basis or the law — that raises a substantial question about the plea’s providence. Courts view the facts in the light most favorable to the Government when a plea is attacked for the first time on appeal.

In Castillo’s case, the court found the military judge’s inquiry thorough and complete. Castillo repeatedly confirmed he knew his wife was asleep. He acknowledged there was no consent. He admitted no reasonable person in his position would have believed otherwise. His own words foreclosed any factual inconsistency that could have required an affirmative-defense instruction.

Why This Case Matters for Military Defense Lawyers

Castillo illustrates the dual-edged nature of affirmative defense instructions in military practice. Here is what defense counsel must understand:

1. Evidence in the Record Triggers the Duty to Instruct

Military judges carry an independent duty to instruct on affirmative defenses when the evidence fairly raises them — even if the defense does not request an instruction. This duty arises from the testimony of any witness, documentary evidence, stipulations, or any other part of the record. The standard is not whether the defense built a strong case for the affirmative defense; it is whether any evidence in the record raises the issue.

In contested cases and at sentencing, this duty operates with full force. If a witness’s testimony suggests the accused held a good-faith mistaken belief, or if documentary evidence creates ambiguity about an element, the military judge must act. Failure to instruct when evidence fairly raises an affirmative defense can constitute reversible error.

2. A Guilty Plea Inquiry Can Dissolve the Duty — If Handled Correctly

When an accused pleads guilty and the record contains no inconsistent matter, the duty to give an affirmative-defense instruction effectively disappears. The judge’s role shifts to ensuring the plea itself is provident — that the accused understands the charge, the elements, and any applicable defenses, and that nothing in the record contradicts the plea.

In Castillo, the military judge correctly identified the potential mistake-of-fact defense when discussing the MRE 412 waiver. She explained the defense to Castillo, confirmed he understood it, and confirmed he was voluntarily giving it up. That colloquy resolved the issue. Castillo’s consistent testimony that he knew his wife was asleep left no room for factual inconsistency.

3. Waiving Motions Has Consequences on Appeal

Castillo also highlights the strategic risks of waiving pretrial motions as part of a plea agreement. When Castillo waived his MRE 412 motion, he foreclosed the very evidence that might have supported a mistake-of-fact defense. Had he gone to trial and the MRE 412 motion been granted, the resulting evidence could have required a mistake-of-fact instruction to the fact-finder.

Defense attorneys must carefully analyze how pretrial motion waivers interact with potential affirmative defenses — both at trial and on appeal. A waiver that seems strategically advantageous during plea negotiations may eliminate viable appellate arguments.

4. Post-Trial Delay: When It Rises to a Due Process Violation

Castillo’s case also addressed excessive post-trial delay. The case took 622 days from sentencing to docketing with the appellate court — more than four times the 150-day benchmark established in United States v. Livak, 80 M.J. 631 (A.F. Ct. Crim. App. 2020). The delay resulted from court reporter workload, software failures, a personal tragedy affecting the court reporter, and a significant miscommunication between the installation and general court-martial convening authority legal offices that went undetected for over 200 days.

Despite the extreme delay, the court found no due process violation. Applying the Barker v. Wingo factors, it concluded that Castillo suffered no cognizable prejudice: he was not subject to oppressive incarceration, showed no particularized anxiety distinguishable from normal post-trial anxiety, and the delay did not impair his ability to pursue his appeal. Castillo also failed to assert his right to timely review before filing his appellate brief.

The lesson: even facially unreasonable post-trial delay does not automatically produce relief. Appellants must demonstrate actual prejudice, or show the delay was so egregious it erodes public confidence in military justice.

Practical Takeaways for Servicemembers Facing Courts-Martial

United States v. Castillo delivers several practical lessons:

Raise affirmative defenses early and preserve them. If any evidence in the record — witness testimony, communications, documentary evidence — supports a plausible affirmative defense, defense counsel must identify it, request an instruction, and preserve the issue for appeal.

Understand what you waive before you waive it. Plea agreements often require waiving pretrial motions. Defense counsel must analyze whether those waivers eliminate affirmative defense arguments at trial and on appeal.

A thorough military judge inquiry protects the government — and can foreclose appellate relief. The more completely the military judge explains defenses and the accused confirms their waiver, the harder it becomes to challenge the plea’s validity on appeal.

Assert your right to timely post-trial processing. Servicemembers who suffer from excessive post-trial delay should document their assertion of that right throughout the process — not just in their appellate brief.

Cave & Freeburg LLP represents servicemembers at courts-martial and before military appellate courts. If you or a family member faces charges under the UCMJ — or if an appeal may be available — contact us for a consultation. We understand how military justice works from the inside, and we fight to protect your rights at every stage of the process. See more at court-martial.com or https://bestmilitarydefenselawyers.com/