A man suspected of beating his father to death while they were both high on methamphetamines will not be prosecuted.

Justin Patrick, 47, died Jan. 22 after a fight with his son.

The autopsy report released this week called it a homicide, saying it was a “sudden death after altercation while under the influence of methamphetamine.”

His son, 20-year-old Jared Patrick, was arrested on suspicion of second-degree murder, but the charges were dropped a week later “pending further results from the autopsy,” according to the Pima County Sheriff’s Department.

Justin Patrick had “blunt force injuries” to his head, neck, chest, abdomen and extremities, including cuts, bruises and scrapes all over his body; edema in his brain and spinal cord; and fractured ribs.

He also tested positive for methamphetamine.

Despite Justin Patrick’s injuries, the Pima County Attorney’s Office will not prosecute his son.

“We’ve reviewed the case and we’re declining to issue charges on it. We believe there’s insufficient evidence to prosecute,” said Deputy County Attorney Ellen Brown, supervisor of the domestic violence unit.

The decision was made after an “extensive” discussion between the county attorney’s office, the sheriff’s department and Dr. David Winston, the forensic pathologist who performed the autopsy, Brown said.

Arrhythmia — an irregular heartbeat — was “the mechanism of death,” said Dr. Gregory Hess, chief medical examiner for Pima County. “The mechanism of death in stimulant drugs such as meth or coke is most often arrhythmia.”

Justin Patrick “died during or shortly after physical altercation thus it is contributory. If he wasn’t involved in the altercation would he have died? That’s part of the thought process,” Hess explained.

During the fight between father and son, Jared Patrick “reported at one point he heard a pop and released his father,” according to the autopsy report. “His father started walking around and after a few minutes suddenly collapsed.”

Deputies responding to a domestic violence call at the family’s home in the 16500 block of West Moore Road, west of Interstate 10, found Justin Patrick on the ground and not breathing.

He was taken to Northwest Medical Center, where he was pronounced dead.

Jared Patrick told detectives he was high on methamphetamines and he used a martial-arts chokehold on his father during a fight, according to court documents.

Dawn Patrick, Jared’s mother, told deputies he was released from prison July 1 after a burglary conviction, court documents state.

She also said Jared Patrick has bipolar disorder and might not have been taking his medication.

Contact reporter Kimberly Matas at kmatas@azstarnet.com or 573-4191.