NASHUA — The man accused of stabbing a local EMT to death and initially claimed he was acting in self defense, may now argue an insanity defense.

Last week, the legal counsel for Matthew Packer, 20, filed a notice of intent to rely on the defense that the actions of Packer were a product of his mental disease or defect, according to paperwork on file at Hillsborough County Superior Court.

The notice goes on to say that Packer “may rely on the defense of insanity in these matters,” including two alternative counts of second-degree murder, alleging that he knowingly and recklessly killed Paul Frontiero III, 27.

Packer is accused of stabbing Frontiero 16 times on Oct. 9, 2011, during a roadside confrontation on Spruce Street. According to police, Frontiero intervened when Packer allegedly held two women at knife point, injuring both of them.

During a previous probable cause hearing, police said Packer claimed he was acting in self defense after a group of about five people allegedly charged him during the confrontation.

Packer, of 36 Carlene Drive, admitted to authorities that he took out a six-inch pocket knife, but only after being punched in the ear during the fight. Frontiero ultimately died of a puncture wound to the heart, but other vital organs, including his left lung, left kidney, diaphragm and spleen were damaged from the numerous knife wounds.

According to the most recent court paperwork, defense attorneys Julia Nye and Caroline Smith are arguing that at the time of Frontiero's death, Packer suffered from mental illness that left him mentally disabled, and that evidence may be introduced to show that his actions were a product of his mental defect.

“Matthew is a 20-year-old man whose mental health history suggests that he suffers from post-traumatic stress disorder as well as other mental illnesses and or defects as a result of a lifetime of physical and emotional abuses,” says the notice, which was filed on June 29.

During the confrontation, Jill Arnold and Kathryn Libby, both of Nashua, were allegedly attacked by Packer. Arnold suffered a knife wound to her throat, while Libby sustained multiple knife slashes to her face, arm, back and rib cage.

In addition to the murder charges, Packer is also facing two first degree assault charges, second degree assault and attempted murder charges for the attacks on the two women, both 29.

The women told police that Packer got out of a car and asked if they wanted to fight. He then approached Libby and allegedly put a knife to her throat. Frontiero, she told police, tackled Packer only after the altercation began, maintaining that none of her friends had any weapons, including Frontiero.

Police also testified that Packer claimed he was bipolar and had not been taking his medication at the time of the assault.

Frontiero worked for EasCare Ambulance Service out of Dorchester, Mass., and was training to become a paramedic. Earlier this year, Frontiero was honored with a posthumous Union Leader Hero Award because of his brave and selfless actions on the night of his death.

Jury selection for Packer's trial has been scheduled for April of 2013, according to court documents.

Two other people have been arrested in connection with the case. Packer's brother, James Packer, 21, of 16 Carlene Drive, and Rosemary Chevez, 18, of 23 Eastern Ave., Amherst, have been charged with hindering apprehension for allegedly helping Packer elude capture following the stabbing.

khoughton@newstote.com