An attorney says he believes a drug-induced psychosis was responsible for an outburst by an actor that police say ended in the slaying of his landlady before the former Sons of Anarchy cast member plunged to his death.

Johnny Lewis, 28, had been arrested three times during the past year and officials were concerned about his mental health and the danger he posed to others. His lawyer Jonathan Mandel, who represented Lewis in the criminal cases, said drugs may have been a factor in the actor's final hours.

"He probably had gotten into marijuana or some medication and that caused him to snap," Mandel said. "If you take certain drugs it triggers that psychosis. A lot of people don't come back."

Katy Perry, who dated Lewis for about a year until they parted ways in 2006 and is said to be heartbroken over the tragedy.

"She had to separate from him to get ahead and focus on her career," a source told Us Weekly.

"He was in trouble then and she couldn't help him. A lot of her songs were partially inspired by him. They had good times. It's really sad. She could never help him and couldn't [let herself] go in that direction."

Authorities said they were still searching for a motive behind the strangulation death of 81-year-old Catherine Davis.

Authorities found Davis and Lewis dead on Wednesday after neighbours reported a woman screaming inside her home that had been ransacked, and where glass was shattered and a dead cat was found. Neighbours said a man jumped a fence and attacked a painter and homeowner next door.

Investigators are awaiting toxicology tests for Lewis to determine whether he had drugs or alcohol in his system at the time of his death.

"(Lewis) being under the influence is something we are looking at based on his behaviour and based on what people have told us about his past," said police Cmdr. Andrew Smith.

The body of Lewis, who played Kip "Half-Sack" Epps on the TV drama Sons of Anarchy, was found in a driveway, and he could have jumped or fallen from the roof, garage or balcony, or tumbled down stairs from a patio area, Smith said. Police said Lewis is the only suspect in the death of Davis.

Probation officials earlier this year expressed concern about Lewis' mental health. The report was prepared in a case in which Lewis was accused of attempting to break into the home of a woman. That case came about six weeks after Lewis hit two men over the head with a Perrier bottle during a fight.

The probation official wrote of being "very concerned for the well-being of not only the community but that of the defendant."

The report added Lewis suffered from some form of chemical dependency and mental health issue, and was a transient.

"Given this, (Lewis) will continue to be a threat to any community he may reside," it said

Lewis was released from Los Angeles County Jail a week ago, according to court records. He had pleaded no contest to assault with a deadly weapon and attempted burglary in separate cases, documents show.

Lewis was earning about US$20,000 a year as an actor and he had been living with his parents when he was first arrested in January. Two probation reports note that Lewis was ordered to stay away from drugs.

Mandel, the attorney, said no drugs were involved in the prior assault and attempted burglary cases. While Mandel knew Lewis had recent, serious mental health issues, he was stunned to learn what had happened.

"I thought the worst that would happen to him would be something dumb like walking on someone's property," Mandel said. "What is alleged of him is so out of the ordinary for him. No one could have envisioned that."

Lewis had been a Scientologist but dropped out in his early 20s, Mandel said. The move could have caused some friction between Lewis and some of his family, who also were Scientologists, although they had been trying to help him out with his troubled, Mandel said.

Mandel said he recommended treatment for Lewis but he declined it.

"I don't think he acknowledged he struggled with drugs," he said. "He felt that he was fine. I know he self-treated, but I don't know if he was an addict. It's certainly a possibility."

Lewis' career spanned more than a decade, mainly in small roles. Among his credits were AVPR: Aliens vs Predator - Requiem, two seasons on TV's The O.C. and Malcolm in the Middle. He was on Sons of Anarchy in 2008 and 2009 before his character was killed off.

- AP