A Calgary jury is deciding the fate of Jeremy Steinke, charged with first-degree murder in the stabbing deaths of his preteen girlfriend's family.

After nine hours of deliberations Thursday, the six-man, six-woman jury was sequestered around 9 p.m. MT. Deliberations continue at 9 a.m. Friday.

Court of Queen's Bench Justice Adele Kent instructed jurors Thursday as "judges of fact" to make a fair decision on Steinke's guilt or innocence, regardless of public opinion, sympathy, prejudice or fear.

"We ask for nothing more," she said. "We are entitled to nothing else."

Kent said that the jurors must believe the slayings were planned and deliberate in order to convict Steinke of first-degree murder, which carries a minimum prison sentence of 25 years before eligibility to apply for parole.

Defence lawyer Alain Hepner argued Thursday that his client did not plan the killings of his girlfriend's parents and brother. (CBC)

She said they can also choose to find him guilty of lesser charges of second-degree murder or manslaughter.

Steinke, 25, has testified that he killed the girl's parents in their Medicine Hat, Alta., home in April 2006, but that it was impulsive, and not planned.

Steinke has also repeatedly denied killing the girl's eight-year-old brother, saying his girlfriend slashed the boy's throat while he watched from a doorway.

The Crown asserts that the couple plotted the killings so they could run away together, because the girl's parents objected to their relationship. Steinke was 23 at the time and the girl 12.

But defence lawyer Alain Hepner argued that his client was in an alcohol- and drug-fuelled haze when he "snapped" and stabbed the girl's parents on an impulse.

"There's no question he's culpable for the deaths of [the parents]," he told reporters after the jury was sequestered. "I argued that there should be a reasonable doubt on the planning and deliberation aspect.

"Jeremy's not going to get away with anything in terms of he's not walking [free] out of this courtroom. There's no question about that. It's just a question of what the proper verdict should be."

Girl would not have been credible: Crown

The victims cannot be named to protect the identity of the girl, who is serving a 10-year youth sentence after being convicted of three counts of first-degree murder last year.

Crown prosecutor Ramona Robins speaks to reporters covering the trial Thursday in Calgary. (CBC)

Crown prosecutor Ramona Robins said she decided not to call the girl as a witness after watching her testify at her own trial last summer.

"It was my assessment she wasn't credible," said Robins.

The Crown lawyer also said she found Steinke inconsistent with his answers on the witness stand.

"The things that he did testify didn't make any sense or at least didn't make sense to me. That's not as a lawyer, that's as a human being, so I thought the jury might feel the same way," said Robins.

But Hepner said he felt it was important his client testify in his own defence, which allowed the jury to hear about his troubled childhood filled with bullying and abuse.

"He had a story to tell. I think it's important in a case like this," said Hepner.

Publication ban lifted

With the jury sequestered, information that the judge ordered held under a publication ban can now be reported.

During the first week of the trial, several jury members wiped away tears as they examined graphic photos of the crime scene that were entered into evidence.

Particularly disturbing were images of the eight-year-old boy lying on his blood-soaked bed, with a wide, deep gash across his throat.

During a break in testimony, Steinke's mother, Jacqueline May, approached one of the jurors, who had been upset by the photos, outside the courtroom.

May said to her, "I'm sorry you have to go through this," prompting the juror to reply, "I can't speak to you," before walking away.

When informed of what happened, Kent said the juror acted appropriately, but she instructed the woman not to tell the rest of the jury members.

Neither the Crown nor defence felt there was a reason for the female juror to be excused from the trial, but Kent imposed a publication ban on the incident until the jury started deliberating.

With files from Bryan Labby, Scott Dippel and the Canadian Press