The Princeton, New Jersey, man accused of killing his brother and a family cat is set to appear in court for the first time Thursday.
Matthew Hertgen, 31, is charged with first-degree murder in connection with the death of his 26-year-old brother, Joseph Hertgen. He is also charged with third- and fourth-degree weapons charges related to possession of a golf club and knife, as well as animal cruelty related to the death of a cat.
Hertgen is expected to appear virtually for a remote pretrial detention hearing in Mercer County on Thursday morning. Due to bail reform in New Jersey, criminal defendants are either charged under a summons and allowed to go home until their court date, or they are charged under a warrant and held in custody until a pretrial detention hearing.
“The prosecutor’s office, in this case the Mercer County Prosecutor’s Office, will decide whether they want to detain you or release you,” David Gelman, CEO of Gelman Law and former prosecutor in New Jersey, told Fox News Digital. “If you’re detained, then you have to have a detention hearing, which is happening tomorrow. And at the detention hearing, they are going to bring up evidence. It’s almost like a mini trial.”
Matthew Hertgen (Mercer County Prosecutor’s Office)
Prosecutors may bring up a “probable cause statement” during the hearing and may even call “a witness or two,” Gelman explained.
There is also a scoring system for criminal defendants in New Jersey, meaning those accused of crimes are assigned a “score” ranging from 1 to 5 depending on the nature of their alleged crimes, with 5 representing the worst offenses, Gelman said.
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Joseph “Joey” Hertgen signs with the University of Michigan as a soccer player. (Toms River Regional School District)
Gelman also anticipates Hertgen’s defense, currently listed as public defender Jamie Hubert, will ask for a mental health examination. The public defender’s office told Fox News Digital that its attorneys do not comment on pending cases.
“I have a feeling there’s some type of mental issue going on here, because you have an individual who’s [in his 30s] and no criminal history whatsoever … a pillar of the community, from what I understand, in a very well-to-do area, Toms River, where he grew up, and he lives in Princeton now, which is very wealthy,” Gelman said. “And for him to be charged with these allegations, which are very disturbing, I have to think that there’s some kind of mental issue that is going on.”
Princeton police initially responded to a 911 call on Feb. 22 at around 11:16 p.m. reporting a fire and a dead body at the Michelle Mews Apartments complex. (University of Michigan | Wesleyan University | Google Maps)
Princeton police initially responded to a 911 call on Feb. 22 at around 11:16 p.m. reporting a fire and a dead body at the Michelle Mews Apartments complex.
Upon arrival, police found Matthew Hertgen, who was determined to be the 911 caller, in the residence along with his brother’s body, which “exhibited signs of blunt force trauma and lacerations,” the Mercer County Prosecutor’s Office said in a press release.
General view of the Michelle Mews housing complex in Princeton, N.J., on Feb. 26, 2025. Matthew Hertgen is alleged to have murdered his brother, Joseph, inside their apartment on Saturday. (Kevin Downs for Fox News Digital)
Authorities have yet to describe any kind of motive related to Hertgen’s murder charges. The suspect had shared some disturbing, graphic poetry to his Facebook profile in September and May 2024.
Joseph Hertgen was pronounced dead at the scene, and his autopsy results are pending. Local and state officials are investigating the 26-year-old’s death as a homicide.
Joseph Hertgen was a University of Michigan soccer player. (Facebook)
Gelman said the community is shocked by the murder.
“This is something that is uncommon, and that’s probably an understatement.”
“Princeton is a very affluent area. … Homes there, minimum, you’re looking at probably 750[,000] and that’s probably like a little shack. So, you’re talking about some big-money areas. And the cops are … very prevalent there because they want to make sure that there’s no crime. It’s a safe area. You have a lot of private schools … so you’re talking about a very, very wealthy, affluent area in Princeton.”
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Both brothers played college soccer: Matthew at Wesleyan University in Connecticut and Joseph at the University of Michigan.
An investigation into Joseph’s death is ongoing. Mercer County authorities are asking anyone with information about the alleged crime to contact the Homicide Task Force Sgt. Will Jett at 609-331-5010 or Det. Karl Johnson at 609-439-5258.
