Insanity and Defendant Testimony

by | Jun 19, 2025 | Blog, Criminal Law, Monmouth County, New Jersey, Ocean County

On December 20, 2024, a three-judge appellate panel decided the Essex County case of State v. Jeremy Arrington. The principal issue under N.J.S.A. 2C:4-1 concerned whether a defendant could testify to their alleged insanity without accompanying expert testimony.

Presiding Judge Sabatino wrote for the Appellate Division in relevant part: Our core point is that there is no reason to believe the Legislature intended to allow the “disease of the mind” requirement under N.J.S.A. 2C:4-1 to be determined solely with lay testimony. We do not foreclose defendants offering lay evidence–including their own testimony if they waive self-incrimination rights–to provide facts that may inform the testifying experts’ opinions and the jurors’ knowledge of the record. For instance, laypersons with personal knowledge under N.J.R.E. 602 who know or have observed the defendant might recount peculiar behaviors they have witnessed. But where, as here, a defendant wants to take the stand and present an amateur self-diagnosis of mental illness without an expert, that is a bridge too far in the absence of a revision of the statute.

Defendant argues he has a Sixth Amendment entitlement to testify as he sees fit and tell the jury why he personally believes he was insane at the time of these atrocious crimes. No case in our state has ever constitutionally required such monologues. Nor has defendant identified any reported opinion from another state utilizing the M’Naghten test that has recognized such a constitutional mandate. We are cognizant that at least two states, Arizona and Ohio, have authorized defendants to present an insanity defense without expert testimony under the M’Naghten test, but those states have not been shown to represent the dominant view. State v. Bay, 722 P.2d 280, 284-85 (Ariz. 1986); State v. Reynolds, 550 N.E.2d 490, 496 (Ohio Ct. App. 1988) (reaching a similar conclusion adopting the Arizona court’s approach in Bay).

Most other states that have addressed the subject in M’Naghten jurisdictions have required expert testimony. For example, in People v. Moore, 117 Cal. Rptr. 2d 715, 723 (Ct. App. 2002), the California Court of Appeal observed that “expert medical testimony is necessary to establish a defendant suffered from a mental disease, mental defect, or mental disorder because jurors cannot make such a determination from common experience.” See also Commonwealth v. Fortune, 302 A.3d 780, 787 (Pa. Super. Ct. 2023) (same); State v. Raine, 829 S.W.2d 506, 511 (Mo. Ct. App. 1992) (same); Doyle v. State, 785 P.2d 317, 322-23 (Okla. Crim. App. 1989) (same). We regard the opinions of these other states to be the sounder approach.

Applying these principles here, we affirm the trial court’s exclusion of defendant’s proposed lay testimony about his alleged insanity. There was no need for the court to conduct a Rule 104 admissibility hearing. The court appropriately exercised its role as a gatekeeper to bar the testimony. See State v. Olenowski (2023) (stressing the court’s gatekeeping function in the admission of opinions about subject matters involving expert methodologies).

This case will almost certainly be appealed to the New Jersey Supreme Court. It concerns a core constitutional right that remains an open question in New Jersey. Those facts make it an ideal case for our state supreme court to address.