Chris Benoit's father doesn't blame steroids.

The doctor who prescribed steroids to Chris Benoit before the wrestler killed his family and committed suicide is serving a 10-year federal sentence, but Benoit's father says it wasn't the drugs that drove his son into a homicidal rage.

Michael Benoit says extensive brain damage from years of trauma in the wrestling ring turned his son into a killer. The professional wrestler strangled his wife with a cord, killed his 7-year-old son with a choke hold and then hung himself.

"The person that committed that tragic act back in June 2007 was certainly not the Chris we knew and loved," his father told the AJC Friday. "Without that brain damage, my son would never have done what he did."

The notion of a steroidal rampage lingers in the public imagination as an explanation for the murders in the family's Fayetteville home.

That is likely in part because steroids were found there and because a toxicology report later indicated that Benoit had about 10 times the normal amount of testosterone in his system when he died.

Also, when the Drug Enforcement Administration raided the office of Dr. Phil Astin III soon after the deaths, they were armed with a search warrant that said he had prescribed, on average, a 10-month supply of anabolic steroids to Benoit every three to four weeks over the preceding year.

Yet experts noted how carefully Benoit had planned the murders. He drugged his son before killing him. That didn't fit the pattern of a "roid rage."

"None of that rings true with steroids, " Dr. Chuck Yesalis, a Penn State University professor regarded as one of the nation's foremost authorities on steroids, said at the time. "I think he was just a very troubled soul."

And, although Astin was sent to prison last year for illegally dispensing drugs, the drugs in question were pain killers, muscle relaxers and tranquilizers. When Astin pleaded guilty in January 2009, assistant U.S. Attorney John Horn told reporters that there was "no evidence in the court record" of a link between Benoit's drug use and the killings.

Michael Benoit said Friday that he didn't know what to think at the time. Then, within days of the killings, a former wrestler and acquaintance of his son approached him with a bizarre request.

Chris Nowinski, who had retired from wrestling because of a series of concussions, was involved in a fledgling effort to study a degenerative disease known as chronic traumatic encephalopathy, or CTE.

Michael Benoit said he didn't know whether to trust Nowinski, but said he was encouraged to participate in the study by the medical examiner for the Georgia Bureau of Investigation, which had preserved his son's body for its forensic exam.

Doctors from Nowinski's group, the Sports Legacy Institute, studied Benoit's brain and found damage consistent with multiple traumas. They said the damage would account for paranoia and depression and could have led Benoit to kill his wife and son.

Benoit's was the fifth brain of an athlete that they had inspected. "He was the worst case they had ever seen," his father said. "He had damage to every part of his brain, right down to his brain stem."

Nowinski's group has joined forces with the Boston University Medical School and over the past two years the joint venture has gotten 300 athletes to agree to undergo a battery of annual tests and to donate their brains after death, according to the Associated Press.

The athlete registry includes former NHL standout Keith Primeau and current Baltimore Ravens offensive lineman Matt Birk, according to a partial list provided to the AP. Donors to the brain bank include former Philadelphia Eagles safety Andre Waters and Penn football player Owen Thomas, both of whom committed suicide.

Those two, like Benoit, showed signs of CTE. The disease has been connected to depression and impulse control issues in NFL players who have sustained concussions.

Michael Benoit lives in Canada and didn't see his son frequently enough to notice a mental decline. But he said the signs at the murder scene -- Benoit had surrounded his victims with bibles -- and a suicide note was found in a bible in a drawer fit the profile of a CTE sufferer.

"He had a hand-written notation in there saying ‘I'm preparing to leave this earth,'" Benoit said.

He said he'd always assumed that fights in the wrestling ring were staged. While it's true they were scripted, he said, his son told him that the beatings with chairs and other furniture caused real damage.

"You're damn right it hurt, dad," his son once told him.