A Princeton man on trial for the killing of his brother has been declared legally insane by a Trenton judge.

The ruling means that Matthew Hertgen will be committed to a mental health facility instead of serving life in prison for the murder of his brother Joe Hertgen.

Doctors who examined Hertgen, from both the state and defense, agreed that the 32-year-old has been suffering from schizophrenia for several years.

They say those symptoms led to delusions and paranoia, leaving him unable to comprehend what he was doing when he attacked his brother with a golf club and knife on Feb. 22, 2025.

That attack took place at the Michelle Mews complex in Princeton.

A forensic psychologist who interviewed Hertgen several times revealed that on the night of the murder, Hertgen was having visions of a spirit, which made him believe he had to commit the act of violence to save his soul.

“Anytime he closes his eyes, he sees tremendous visions," said forensic psychologist Dr. Gianni Pirelli.

Pirelli also testified that Hertgen "Believes that the spirit that overtook him in 2021 is basically too powerful for any medications or mental health treatment that would come about."

At the time of the murder, Hertgen was not taking anti-psychotic medication. His family says it was his first act of violence.

In handing down his ruling, Mercer County Superior Court Judge Robert Lytle said, “In his delusional state, the act was not wrong in the ordinary moral sense. It was required. The court finds the defendant is not criminally responsible for his actions because at the time of the relevant conduct, he was laboring under such a defect of reason from disease of the mind."