## Facts

- Joseph Santarelli shot and killed his brother-in-law, Joseph Foti, with a sawed-off shotgun in a two-family home where their families lived in separate units.
- Forensic evidence indicated Foti was first shot from above while on a stair landing; after attempting to flee, he was shot again and died.
- Santarelli admitted the shooting but asserted an insanity defense under N.Y. Penal Law § 30.05, offering lay and expert evidence of mental illness.
- The prosecution countered with psychiatric testimony that Santarelli was not psychotic but had an “explosive personality,” a disorder involving violent outbursts short of legal insanity.
- Over objection, the prosecution introduced multiple prior incidents and a prior conviction to support that diagnosis, including testimony about a bar fight of unclear origin, a planned beating, prior conviction for possessing a sawed-off shotgun, and other violent or threatening behavior reported by a probation officer.

## Issues

1. When a defendant raises an insanity defense, to what extent may the prosecution introduce prior uncharged violent or antisocial acts (and a prior conviction) as evidence bearing on sanity through a psychiatric diagnosis.
2. Whether the challenged prior-acts evidence, though offered as relevant to sanity, was so excessive, cumulative, or inflammatory that it functioned as impermissible propensity/character evidence and unfairly prejudiced the jury.

## Decision

- The New York Court of Appeals reversed the conviction and ordered a new trial.
- The court accepted that some prior misconduct can be admissible once sanity is placed in issue, if it is genuinely probative of mental condition.
- The trial court erred by admitting the volume and detail of prior violent-acts evidence, much of which was only loosely connected to the sanity inquiry.
- The cumulative presentation risked a verdict based on the defendant’s perceived bad character rather than his criminal responsibility at the time of the homicide.
- Because insanity was the central disputed issue and the prior-acts evidence played a prominent role, the error was not harmless.

## Legal Principles

- Once a defendant puts sanity in issue, the prosecution may offer evidence of prior criminal or antisocial conduct to the extent it is probative of sanity.
- Prior-acts evidence offered on sanity must be carefully limited; psychiatric relevance does not permit admission of every prior misdeed.
- Trial courts must exclude prior misconduct evidence when its prejudicial effect substantially outweighs its probative value or when it becomes unnecessarily cumulative.
- The prosecution may not use an expert’s diagnostic label to bootstrap otherwise improper character or propensity evidence into the case.

## Conclusion

The court held that rebuttal of an insanity defense may include prior conduct bearing on mental condition, but the trial judge must tightly control such proof to prevent the jury from convicting on propensity grounds; the excessive prior-acts evidence required reversal and a new trial.


People v. Santarelli, 401 N.E.2d 199 (N.Y. 1980)