Authorities had been interested in whether Johnny Lewis was on drugs or medication when he apparently killed Catherine Davis in her home and then fell to his death in her driveway.
Lewis had recently been released from jail and had a string of drug-related arrests before the killing. His attorney had speculated he might have been in a drug-induced psychosis when he killed Davis.
Toxicology results on Johnny Lewis found no traces of cocaine, alcohol, marijuana or any other types of drugs in the actor's system. Officials checked for anti-psychotic drugs as well as psychedelic drugs.
An autopsy report noted that Lewis had nail marks on both sides of his neck when he died and had suffered partial strangulation. His death was ruled accidental because there was no evidence he attempted to kill himself or had been pushed.
Police believe Lewis fell while trying to flee the home after killing Davis, 81, who operated a retreat for writers and actors out of her home.
Lewis had played Kip "Half-Sack" Epps on the TV drama "Sons of Anarchy" in 2008 and 2009 before his character was killed off.
He had been arrested three times during the past year. Probation officials earlier this year expressed concern about Lewis' mental health and his danger to others.
A probation officer who evaluated Lewis' case after he attempted to break into the home of a woman wrote that he was 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
The break-in attempt came about six weeks after the actor hit two men over the head with a bottle during a fight.
Lewis' attorney, Jonathan Mandel, said after his client's death that drugs may have been a factor in the deaths. He said he recommended treatment for Lewis but he declined it.