A judge found Matthew Dieringer incompetent to stand trial in the Scottsdale beating death of Frank Quaranta.

Incompetent to stand trial does not mean not guilty, and it does not mean insane. It means the court found that, right now, he cannot understand the proceedings or help his own lawyer. FOX 10 reported two experts found him competent and a third did not, and the judge's ruling followed the third. The case pauses. It does not end. The ruling also said there is no clear evidence he will be restored within the standard 15 months.

FOX 10 Phoenix reported Wednesday, Oct. 7, 2026, that a judge ruled Matthew Dieringer, 36, incompetent to stand trial on a first-degree murder charge in the death of Frank Quaranta, 67. Under Arizona law, a defendant is incompetent when mental illness or disability leaves the person unable to understand the proceedings or to assist in the defense, the station reported. Dieringer has been placed in a competency-restoration program within Maricopa County Correctional Health Services, which carries a standard 15-month timeframe, and the judge stated there is no clear evidence he will be restored within that period, FOX 10 reported. His next court hearing is Nov. 12.

According to FOX 10, two mental health experts found Dieringer competent, while a third diagnosed him with delusional disorder, compulsive personality disorder, narcissistic personality type, and a paranoid personality style. The ruling says he believes he is the target of a conspiracy because of his self-proclaimed celebrity status, and one expert documented his frustration that his lawyer would not treat his "social media influence" as relevant to the case. The court described him as "uncooperative and irrational" with delusional thoughts when he is not medicated. FOX 10 reported he had twice been found competent in earlier Arizona cases.

The competency proceedings, known in Arizona as Rule 11, began after a Jan. 22, 2026, hearing at which Dieringer said, "Here comes the Rule 11. It's all scripted!" FOX 10 reported. At that hearing his defense attorney told the court Dieringer would not talk to him, and Dieringer said he wanted to fire his lawyer. When the judge told him to file a motion, he answered, "How about I just write a letter to the FBI, and I've already done that," according to the station.

Arizona's Family reported that officers doing a welfare check on Labor Day 2025 found Quaranta dead in his townhome near 68th Street and McDowell Road after he did not show up for work, and that the medical examiner found multiple skull fractures, a broken jaw, a neck fracture, and broken ribs. Court documents described by Arizona's Family say Dieringer had been living with Quaranta for several months, that Quaranta had asked a co-worker how to get him to move out, and that DNA testing of a bloody shirt and socks showed "very strong support for inclusion" of both men's DNA. FOX 10 reported the two met at a heat relief center where Quaranta worked. Arizona's Family reported they met through a homeless outreach group connected to Quaranta's church. Those are the state's allegations. They have not been tested at trial.

Dieringer's record reaches into Colorado. Arizona's Family reported the Teller County Sheriff's Office issued a warrant for him in July 2020 over the beating deaths of his roommate's two dogs, and that he pleaded guilty to felony aggravated animal cruelty and was sentenced to 18 months in prison. FOX 10 reported he was on supervised probation in Arizona after pleading guilty to theft in April 2025. Prior convictions are his record. They are not proof of the murder charge. All defendants are presumed innocent until proven guilty in a court of law.