PORTLAND — The jury in William Hanaman’s murder trial should have been instructed to consider whether he acted in the heat of passion when he stabbed his former girlfriend 17 times, his lawyer argued before the Maine Supreme Judicial Court on Thursday.

Hanaman, 53, is serving a 40-year prison sentence for killing Marion Shea.

On Nov. 10, 2009, Hanaman persuaded Shea, 47, to go to his apartment in Portland even though it was prohibited by a bail condition stemming from a domestic violence charge against him.

At one point, he found her with a plastic bag containing empty pill bottles and cut straws, and saw it as evidence of her drug abuse that he intended to present in his court case.

Hanaman tried to grab the bag. Shea pulled back. The bag ripped open and pills flew out. Hanaman testified that he saw a “shiny object” in her hand, then felt sudden fear and his system shutting down. He testified that he blacked out and woke up miles away, in his truck.

After finding Shea’s body in his home, he tried to kill himself with an overdose of her painkillers. The next day, police found Shea’s body and Hanaman, barely breathing, in the apartment.

The trial judge told the jury to consider whether Hanaman acted in self-defense, but decided not to instruct jurors about “adequate provocation” — the heat-of-passion defense, which involves extreme anger or fear.

Robert Levine, Hanaman’s lawyer, argued Thursday that the jury could have convicted Hanaman on the lesser charge of manslaughter if it had been told to consider that defense. Had the jury determined that Hanaman acted in self-defense, he would have been acquitted on the murder charge.

Levine told the justices that Shea’s killing was the act of an angry man, even though he didn’t testify to being angry. Levine also argued that Hanaman’s reaction should be seen in the context of Shea’s previous acts of violence against Hanaman.

Justices asked what element of the incident that led to the stabbing could constitute adequate provocation to kill another person.

“What he’s doing is, he’s committing victim tampering, witness tampering, in a domestic abuse case,” said Justice Donald Alexander. “She’s defending herself from this attack — in a domestic abuse case — and you’re saying the fact that she defends herself provides an adequate provocation to kill her? That’s what you want us to rule?”

Levine answered that he did not believe Shea had the right to defend herself with deadly force. He also disputed that Hanaman was attacking Shea when he tried to take the bag from her.

Assistant Attorney General Donald Macomber argued that the evidence in the case simply did not warrant an “adequate provocation” manslaughter instruction to the jury.

“He said he wasn’t angry. He said he had sudden fear when he saw the shiny object … He removed the shiny object from her hand: end of fear,” Macomber said. “He didn’t say he killed her because he was fearful. In fact, he said, ‘I don’t remember killing her.'”

The court did not indicate when it will issue its ruling.