At oral argument in People v. Madison, attorneys debated whether Michigan trial courts may admit diminished-capacity evidence to negate mens rea or to inform the reasonableness prong of a self-defense claim. The parties argued before the Michigan Supreme Court on an application seeking permission to present expert and fact-witness evidence that the defendant’s mental symptoms affected his perception and capacity.

Attorney Christopher Wirth, representing Seneca Madison, told the justices that expert opinion in the case suggested Madison “could have imagined that the alleged victims were talking about him and planning to kill him, potentially impairing his capacity, thus causing him to act in what he believed was genuine self defense.” Wirth said trial courts’ exclusion of diminished-capacity evidence under People v. Carpenter denies juries relevant information about a defendant’s perception and the reasonableness of defensive conduct, and urged the court to allow such evidence to mitigate malice and specific intent charges.

Gabrielle Barber of the State Appellate Defender Office, appearing for criminal defense amici, urged the court to reconsider Carpenter, calling it wrongly decided and arguing that exclusion of diminished-capacity evidence can prevent juries from considering evidence relevant to specific intent. Barber framed the stare decisis analysis around workability, reliance interests and changes in fact or law.

Allison Schultz, arguing for amici including the American Psychological Association and Michigan Psychological Association, told the court modern psychological research distinguishes symptoms that bear on mens rea from those that bear on legal insanity. Schultz described categories of evidence—information-processing deficits, diminished impulse control and disorganization—that, she said, can be probative of a defendant’s ability to form premeditation or specific intent without necessarily meeting the statutory test for legal insanity.

The prosecutor, John Donaldson for the People of the State of Michigan, argued the relief sought by Madison would go beyond pre‑Carpenter diminished-capacity practice and could collapse the statutory insanity framework into an affirmative route to acquittal in cases where experts say a defendant perceived threats that were not real. Donaldson warned that allowing the evidence as a basis for a self-defense justification risks returning individuals with serious mental illness to the community without treatment and emphasized the legislature’s creation of postconviction procedures for those found not guilty by reason of insanity or “guilty but mentally ill.”

Multiple justices pressed both sides on practical consequences. One justice asked whether overturning Carpenter would encourage defendants who might otherwise pursue an insanity defense to instead seek diminished-capacity strategies to avoid civil commitment; Wirth, a trial attorney, responded that competent counsel would still weigh the distinct risks and benefits, including the possibility of conviction for a lesser offense and substantial sentencing consequences. Justice Thomas specifically asked whether diminished-capacity claims should be subject to a notice requirement; amici acknowledged that some court of appeals precedent has required notice but urged courts to focus on symptom-specific evidence and gatekeeping principles for expert testimony.

Counsel and amici also debated the proper interpretive lens for the criminal responsibility statute and the “guilty but mentally ill” provision. The prosecutor cited prior Michigan and U.S. precedent upholding Carpenter and argued that many of the defense’s proposed uses of diminished-capacity evidence are properly addressed within the insanity framework. Defense and amici countered that diminished-capacity evidence is conceptually distinct from legal insanity and that trial judges routinely evaluate expert testimony’s probative value and potential prejudice.

The argument closed without a decision from the court; the bench announced the case would be submitted.

Why it matters: the court’s ruling could change whether juries may hear expert testimony about how a defendant’s mental symptoms affected his ability to form specific intent or to reasonably perceive threat. That outcome would affect how criminal trials handle expert mental-health evidence, whether some defendants pursue insanity pathways or trial defenses, and how trial courts apply gatekeeping standards to psychiatric and psychological testimony.