MARBLEHEAD — Prosecutors say that when Rocco Nuzzolo learned that his former girlfriend was with someone else in the early morning hours of Thanksgiving 2007, he invaded the woman's home armed with a beer bottle and attacked the other man.

But Nuzzolo offers a defense: He went to the home not to attack the other guy, but to help his ex with what he believed was a substance abuse problem.

"In essence, this was not an invasion," said defense lawyer P. Christopher DiOrio. "This borders on an intervention. You see intervention shows on A&E. You don't prosecute them."

Whether the defense flies with a Salem Superior Court judge is another matter, as Nuzzolo's trial on home invasion and assault and battery with a dangerous weapon charges got underway yesterday.

Nuzzolo, 28, waived his right to a jury and is asking Judge Howard Whitehead to decide his guilt or innocence.

DiOrio contends that prosecutor Marcia Slingerland cannot prove essential elements of the crime of home invasion, including whether Nuzzolo actually brought the beer bottle, his weapon, to the home that night.

Slingerland told the judge in an opening statement that Nuzzolo's former girlfriend was at home in a Pleasant Street apartment with a male friend, drinking beer and watching television.

Meanwhile, the woman's roommate had gone to a bar, the Riptide, where she ran into Nuzzolo.

Around 12:30 a.m., the woman heard a knock on the door to her bedroom, Slingerland said.

The woman assumed it was her roommate and opened the door, only to find Nuzzolo coming into her bedroom, carrying a beer bottle and, allegedly, a brick that had been left outside the apartment door.

Nuzzolo and the other man got into a fight, during which the other man suffered a head wound, Slingerland said.

DiOrio argued that the allegations "in no way constitute any kind of invasion."

He said the woman's roommate expressed concern about her, telling Nuzzolo, "You are the only one she seems to listen to."

"She sent him there not to create an incident but to talk to (her)," DiOrio said. "He's here because he cared, and that's not a reason to be here."

The trial is expected to conclude today.