Whether the prosecution could introduce weapons found in the defendant's apartment that were not used in the killing and were not carried to the scene.
Holding
No. The weapons were inadmissible because their real purpose was to show that the defendant had a murderous criminal disposition and therefore was more likely to have committed premeditated murder.
Reasoning
The decisive factual question was Zackowitz's state of mind when he fired: whether he acted after deliberation and premeditation or instead under the sudden force of anger, intoxication, or both. That inquiry was close and subtle. The jury therefore had to decide it without evidence likely to substitute prejudice about the defendant's character for proof of his mental state at the moment of the homicide.
The additional pistols and tear-gas gun had no direct connection to the shooting. The prosecution did not contend that Zackowitz used, carried, or displayed them during the confrontation; indeed, they were of different calibers from the murder weapon and remained in his apartment. Their only meaningful relevance was the forbidden inference that a person who possesses such weapons is a dangerous person, and thus more likely to have killed deliberately.
The governing rule is that a criminal defendant's character is not in issue unless the defendant elects to place it in issue. Although a propensity inference may have some logical force, the law excludes it as a matter of policy because jurors may give a supposed criminal disposition excessive weight or punish a defendant for being a bad person rather than for the offense charged.
The result would differ if the weapons had been acquired in preparation for this particular encounter, connected the defendant to the crime, or had been carried by him at the time of the confrontation. In those circumstances, they could tend to establish preparation, design, or identity. Mere ownership of weapons left at home establishes none of those permissible purposes.