TRENTON, N.J. (Court TV) — A New Jersey man has been found not guilty by reason of insanity after brutally murdering his brother while experiencing psychotic delusions.
Matthew Hertgen appears in court for his murder trial on March 18, 2026. (Court TV)
Matthew Hertgen was charged with first-degree murder, weapons offenses and third-degree animal cruelty after killing his younger brother, Joseph Hertgen, with a knife and a golf club. At a bench hearing on Wednesday, Judge Robert Lytle agreed with experts from both prosecutors and the defense that the defendant was insane at the time of the killing.
Police were called to Joseph Hertgen’s home on Feb. 22, 2025, when Matthew Hertgen called 911 to report that his brother was dead on the floor and had been there for approximately 30 to 40 minutes. When dispatchers asked how the victim was hurt, Matthew Hertgen responded, “I’m not gonna go into any more details right now.”
When officers arrived, they found Joseph Hertgen on the floor with a large pool of blood around his head and torso. He appeared to have suffered severe blunt force trauma to the back of his head and a laceration to his chest and abdomen that exposed the chest cavity. Investigators also noted cuts to the victim’s right eye, and said his right eyeball was not visible. Also in the house, a dead cat was on an ottoman in the living room; the animal had been beaten, stabbed and set on fire.
Matthew Hertgen never denied his role in the murders, but told his family, doctors and defense team that he had been suffering from “visions.”
Dr. Gianni Pirelli, a clinical and forensic psychologist, was the sole witness called during the trial; he testified that Matthew Hertgen was schizophrenic and had struggled with his mental health since 2021. Pirelli said the defendant suffered from frequent “visions,” including delusions and hallucinations that often took religious and apocalyptic overtones.
“I don’t say this lightly, and I certainly don’t want to make Matthew or his family feel bad, but I think it’s important for me to say that when I saw him, and based on my record review, he has one of the most severe mental illnesses that I’ve seen,” Pirelli said. “I say that not on a whim, but I say that because Matthew is constantly psychotic. He indicates, just even anytime he closes his eyes, he’s seeing tremendous visions.”
Pirelli said that the defendant still struggles to comprehend the situation. “He’s still trying to understand what all these thoughts or beliefs are,” Pirelli said. “He’s willing to call it psychosis, kind of for our benefit to have the conversation, and he wants to be able to try to get help and some relief, but he believes that the spirit that overtook him in 2021 is basically too powerful for any medications or mental health treatment.”
Because Matthew Hertgen was found not guilty by reason of insanity, he will remain in the custody of the jail until sentencing, at which point he will be placed in a mental hospital. Sentencing is scheduled for May 1.
