A former OPP drug investigator entered a Newmarket court Wednesday for the start of his own second-degree murder trial.

Paul Kenyon is accused of murdering his ex-girlfriend Marion Deacon and then burning her Gormley house down on March 7, 2010.

Though he was once an OPP officer, Kenyon quit in 1991. A source said his own suspected drug use lead to his resignation.

Kenyon became a crack addict, his defence lawyer, Ken Murray, said.

Murray said Kenyon was a thief who frequented prostitutes, saying that Kenyon's only salvation was his girlfriend, Deacon.

The court heard that Deacon had kicked Kenyon out after she found his crack pipe. She told him to get clean, or the relationship was over.

On the night she was murdered, Kenyon and Deacon were supposed to meet for a heart-to-heart conversation, the court heard.

In the morning, firefighter Don McClean found Deacon, dead and beaten. She was still wearing her coat and waitressing uniform from the night before.

"Her face appeared badly beaten up," McClean said. "It looked like a mask."

A bloody baseball bat was also found inside the house.

The trial continues Thursday.

With files from CTV Toronto's Tamara Cherry