10/21/2014 02:09 EDT | Updated 12/21/2014 05:59 EST

Calgary detective believed Derek Puffer hearing voices, court hears

The Crown lawyer has concluded the case against Derek Puffer following the presentation of a videotaped interview where the 40-year-old tells police he killed his mother and step-father because of voices in his head. 

Puffer faces two counts of second-degree murder.

Today, Det. Patricia Allen, who interviewed Puffer, told the court she believed he was hearing voices again during the three-hour interview and described him as being in a trance-like state at times.

The judge has released that video and portions will be published on CBC's website later today.

The trial, which began Monday heard that Donna Lee and Bill Powers were stabbed a total of 25 times in their sleep in July.

Puffer has pleaded not guilty and his lawyer, Alain Hepner, told Justice Kristine Eidsvik the issue in this case is not whether Puffer committed the crime, but whether he is not criminally responsible because of mental illness.  

On the tape, Puffer tells the detective he'd been hearing voices and music in his head for days. 

"I blacked out and did a lot of irrational things, it was bizarre. It wasn't me, I just lost control of who I was," said Puffer.

He also told the detective the voices told him to: "Go get Billy."

Bill Powers was a well-known sports retired in October 2009 after almost 50 years in the sports broadcasting and communications business.

The court heard that Puffer was found that night naked with blood on his hands at a nearby bus shelter at 14th Street and Southland Drive.

He told police he suffers from schizophrenia and hadn't taken his medication for nearly 20 years. He also said that  the couple had put a computer chip in his brain and that he was hearing voices asking him about a knife.

During his testimony, Const. Michael Green, who found and arrested Puffer, described the accused at the time as "stoic, emotionless and calm … cool as a cucumber."

Puffer is expected to testify Wednesday. The trial is scheduled to last all week.