Steven Simminger's paranoid schizophrenia and anxiety were well documented, developing after a 1994 auto accident in the Navy cost him a leg, and left him with a traumatic brain injury and a disability discharge.

But does that mean Simminger, 41, was legally insane early on March 13, 2016, when he fatally stabbed a man in Rittenhouse Square during an altercation over Simminger's Jersey Devils sports cap?

Assistant District Attorney Andrew Notaristefano says Simminger's mental problems don't come close to meeting the tough legal standard for insanity.

But defense attorney Gina Capuano won a preliminary victory Thursday when Philadelphia Common Pleas Court Judge J. Scott O'Keefe denied a prosecution motion to bar use of an insanity defense at Simminger's Nov. 13 trial. Capuano argued that an insanity defense is possible, or that evidence about Simminger's mental state might at least convince a jury that he believed his life was in danger and stabbed Colin McGovern, 24, in self-defense.

While not promising he would let the jury consider an insanity verdict, O'Keefe said Capuano should be permitted to present evidence of Simminger's mental problems and their possible impact on his behavior.

For Simminger, of Media, O'Keefe's ruling could mean the difference between life in prison without parole and a lesser sentence, or even acquittal.

Successful insanity defenses are rare because the legal standard is so difficult: The person must be so mentally ill that he or she cannot understand the consequences of the behavior and the difference between right and wrong.

Notaristefano told O'Keefe there was no legal basis for bringing evidence of mental illness into Simminger's trial. He said Capuano is trying to buttress a self-defense theory and persuade the jury to return a manslaughter verdict.

"It will just confuse the jurors," Notaristefano said.

"This is a first-degree murder case," said Capuano, arguing that evidence about Simminger's mental state would show that he acted in self-defense.

"In his belief, what he was doing was right," Capuano said.

The events culminating in McGovern's death about 2 a.m. began 12 hours earlier when the Churchville, Bucks County, man and several friends came to Center City for the "Erin Express," a day of partying on the Saturday before St. Patrick's Day.

Early that morning, McGovern, a friend, and two female companions were at 19th Street and South Rittenhouse Square looking for a place to crash for the night.

At last year's preliminary hearing, a witness said McGovern or his friend stopped Simminger and said, "So you're a Jersey Devils fan."

There was an argument, a fight, and then the words, "He has a knife."

The witness said she saw McGovern walk toward her with a red stain spreading over his chest and then collapse.

The autopsy showed that McGovern had been stabbed 11 times.

A surveillance video screened at the hearing showed McGovern and Simminger standing and facing each other. In the video, Simminger swings at McGovern, who lunges at Simminger, and they fall to the ground with McGovern on top of Simminger.

The video shows Simminger getting up and walking away while the mortally wounded McGovern walks toward the camera.

Simminger was found by police almost four hours later at the Philadelphia VA Medical Center in University City.