Jeremy Steinke was "in a haze" when he fatally stabbed his girlfriend's mother and found himself face to face with her father, who tried to defend his family with a screwdriver, a Calgary jury heard Tuesday.

Steinke, 25, is accused of helping his girlfriend murder her family in April 2006. The bodies of the victims - the girl's parents and eight-year-old brother -- were found in their Medicine Hat home by a neighbour.

On Tuesday, jurors heard a taped conversation between Steinke and an undercover police officer, Cory Both, who was posing as an inmate. It was recorded as Steinke was transported from Medicine Hat to Calgary in a court transfer van.

On the audiotape, Steinke is heard describing how he slipped into the basement through a window. He was then confronted by the girl's mother. He stabbed her, and the father heard his wife scream.

"He came barrelling downstairs ... and came at me real fast," Steinke says. "The last thing I really remember was him attempting to stab me."

The father missed with the screwdriver, instead hitting Steinke's sweater, according to his description of events on the tape.

"The last thing I remember is him ... lying on the ground asking me, `Why?" says Steinke.

He says he told the father it was because he had mistreated his daughter. He then says he went upstairs and "watched my girlfriend cut her brother's throat."

The girl's parents had tried to stop the couple from seeing each other because of their age difference. Steinke was 23 at the time, while his girlfriend was 12. She has already been convicted of three counts of first-degree murder and is serving a 10-year sentence.

Because of her age at the time of the murders, she cannot be identified under the Youth Criminal Justice Act. As a result, the victims also cannot be identified.

In the taped conversation, Steinke says he was intoxicated and high on drugs when the family was killed, and that he wasn't responsible for killing his girlfriend's young brother.

At another point in the conversation, he boasts that the murders will make him and his girlfriend famous, and refers to the Oliver Stone film "Natural Born Killers," about a couple that embarks on a killing spree.

On Tuesday, jurors also heard testimony from Steven Durk, a provincial sheriff. He alleged that Steinke had told another inmate about killing the girl's parents.

Durk also testified he overheard Steinke say he was not sober at the time of the killings.

The trial has been moved to Calgary because of the intense media coverage the case attracted in Medicine Hat.

With files from CTV Calgary and The Canadian Press