Background
Jeremy Arrington was charged with 29 offenses arising from a 2016 attack in a Newark apartment. The evidence showed that he bound and stabbed occupants, forced a child to stab four victims, and shot one victim. Three people died. After a three-day hearing at which experts disagreed about whether Arrington was malingering, the trial court found him competent to stand trial.
Arrington intended to raise an insanity defense but did not retain an expert to support it. He proposed testifying that he did not know his actions were wrong. The trial court ruled that he could not present an insanity defense without expert testimony, although he remained free to testify about his state of mind or version of events. A jury convicted him on 28 counts, and the Appellate Division affirmed.
The Court’s Holding
The New Jersey Supreme Court unanimously affirmed, holding that a defendant must proffer expert testimony to assert an insanity defense under N.J.S.A. 2C:4-1. Determining whether a defendant had a “disease of the mind” and whether it prevented the defendant from understanding the nature or wrongfulness of the charged conduct involves complex matters beyond an average juror’s common knowledge.
The required expert need not necessarily be a psychiatrist or psychologist, but the witness must possess relevant expertise and satisfy N.J.R.E. 702. Lay witnesses, including the defendant, may offer admissible evidence that complements expert testimony, but lay testimony alone cannot establish the foundation necessary to submit insanity to the jury.
The Court also concluded that Arrington’s proposed evidence would have been insufficient even without a categorical expert-testimony rule. His planned testimony was uncorroborated, the gruesome nature of the crimes did not itself indicate legal insanity, and the record included evidence that he may have feigned mental illness. Excluding the defense therefore did not violate his constitutional right to present a complete defense.
Key Takeaways
- A New Jersey defendant may not present an insanity defense based solely on the defendant’s testimony or other lay evidence.
- A qualified expert must identify a disease of the mind and explain its effect on the defendant’s ability to understand the act or its wrongfulness at the time of the offense.
- Lay testimony remains admissible when it satisfies the evidence rules, but it may only supplement the required expert proof.
Why It Matters
The decision establishes a bright-line evidentiary prerequisite for insanity defenses in New Jersey. Defense counsel must secure admissible expert support connecting a qualifying mental condition to the defendant’s reasoning at the time of the alleged offense before the issue may reach a jury.
The ruling also confirms that the constitutional right to present a defense remains subject to evidentiary gatekeeping. A defendant’s assertions, unusual behavior, or the shocking character of the offense cannot substitute for reliable expert evidence on legal insanity.