10/20/2014 03:32 EDT | Updated 12/20/2014 05:59 EST

Suspect in death of popular Calgary sportscaster, wife pleads not guilty

CALGARY - A suspect in the death of a popular one-time Calgary sportscaster and his wife has pleaded not guilty to second-degree murder.

A hearing is being held in court to determine Derek Puffer's mental state at the time Bill Powers and his wife, Donna Lee, were killed.

The couple were found dead in their home in July 2013 — court heard they had been stabbed 25 times.

An agreed statement of facts says Puffer told officers at the time of his arrest that he'd been hearing voices and also asked police if they'd found "the knife."

Puffer, Lee's adopted son from her first marriage, was living with the couple.

It’s expected the defence will try to prove Puffer was not legally sane at the time of the killings because he is schizophrenic.

"They’re in the bedroom. They put a chip in my brain," the statement of facts quotes Puffer as saying.

Powers retired in October 2009 after almost 50 years in the sports broadcasting and communications business. He worked mainly in radio and was also media co-ordinator for a time for the CFL Calgary Stampeders.

(CHQR, The Canadian Press)