State v. Jeremey Arrington

Summary

The Court held that a defendant must present qualified expert testimony to assert New Jersey’s insanity defense because diagnosing a mental disease and determining its effect on the defendant’s reasoning at the time of the offense are beyond the common experience of jurors. The requirement does not eliminate the possibility of complementary lay testimony, but lay testimony alone cannot establish the defense. Applying that rule, the Court affirmed because Arrington offered only his own proposed testimony and no expert evidence.