The actor accused in the shooting death of an off-duty policeman testified Monday that he didn't know his alleged accomplice was armed when he went to an apartment looking for drugs.

Taking the witness stand in his own defense at his murder trial in the Bronx, Lillo Brancato, who got his big breaking opposite Robert De Niro in the 1993 film "A Bronx Tale," sought to fend off suggestions by the prosecution that his testimony — at times punctuated by vignettes about his drug-crazed downfall — was another acting job.

"Is this a role you're playing today?" his attorney Joseph Tacopina asked at the end of a daylong stint on the witness stand.

"Absolutely not," the 32-year-old defendant responded.

Brancato — also is known for playing a wannabe mobster on the HBO hit "The Sopranos" — is charged with second-degree murder in the December 2005 shooting death of Officer Daniel Enchautegui.

Authorities say Armento and Brancato broke into the basement apartment to steal prescription drugs after a night of drinking at a strip club. Enchautegui, who lived next door, came out to investigate.

Armento blasted the 28-year-old officer with his .357 Magnum, hitting him in the heart. The dying officer fired back, wounding both men. Armento was convicted earlier this year of first-degree murder.

Brancato testified that there was a never a break-in. He claimed that he had known the owner, a Vietnam veteran, for several years. He also said he had permission to go inside and take painkillers and other pills whenever he felt like it, and didn't know the man had died earlier that year.

The pills were part of a drug problem that he said began when he was "introduced to marijuana" on the set of "A Bronx Tale." He later became hooked on crack and heroin, he said.

He told the jury that while suffering from judgment-impairing heroin withdrawals on the night of the shooting, he accidentally broke the kitchen window of the apartment in a desperate attempt to wake up his old pill-supplier.

"I was becoming dope sick," Brancato testified. "Mentally, I was a mess."

Brancato and Armento left momentarily to try to get drugs from a drug dealer. When that failed, they returned to the basement apartment and came face-to-face with the officer.

"I heard someone say, `Don't move,"' Brancato said. "I turned around quickly and I was shot twice."

Brancato said he ran away, not knowing he'd been shot by a police officer. When uniformed officers stopped him, he lifted up his shirt to show them he was wounded.

"Please help me," he said he told them. "I don't want to die."