CALGARY -- The Crown in a double murder trial of a woman accused of killing her babies says she was not initially a suspect when police began investigating her.

Jayme Williams was responding to defence arguments that Meredith Borowiec's charter rights were violated in a police video interview in 2011.

Williams said police were only looking into two of the Calgary woman's pregnancies when they began interviewing her and didn't need to caution her that she could face murder charges.

"They were in fact investigating her previous pregnancies," Williams told the judge hearing the case on Wednesday.

"No officer indicated there was any infant born or evidence a live birth had been recorded," she said.

"You only have a human being if the person has taken a breath. There's nothing to indicate the lives could have been ended by an unlawful act."

Borowiec, 31, is charged with second-degree murder in the deaths of two newborns in 2008 and 2009. She was charged just over a year after a third child was found alive in a Dumpster in October 2010, which prompted a lengthy police investigation.

She faces a second trial this fall on an attempted murder charge related to the surviving child.

Lawyers are arguing whether the video, in which Borowiec admits to placing her newborns in a trash bin, should be admitted as evidence.

Justice Peter McIntyre told the lawyers he has his work cut out for him and will rule next Tuesday on whether to allow the videos to be entered as evidence in the trial.

The defence says Borowiec's charter rights were violated in a number of ways, including not warning her she was a suspect in the two deaths when the video was taken. The interview was done in relation to the abandoned child and her lawyers say police should have let her know about the consequences.

Police officers had their suspicions but no proof from any source, Williams said.

"With regard to all of the witnesses, each indicates they had no information of a live birth or a birth at all."

Williams also rejected suggestions that the investigating officer's interview method led Borowiec to confess to something she did not do.

"There is no evidence before court that the accused had a change of memory from talking to police officers," she said.

"The accused does know what happened and is able to provide detail."

Defence lawyer Andrea Serink said her client's treatment "shows a pattern of disregard throughout the investigation of her most basic charter rights."

Borowiec was first interviewed by police after the live baby was found in the trash bin. In that video, Borowiec says she had her first child in 2008 and didn't even look to see whether it was a boy or a girl before she wrapped the infant in a towel and put it in a garbage bag.

She admits to the same scenario in 2009 when she again gave birth into a toilet in her apartment, wrapped the child in a towel and dropped it into the bathroom garbage before walking out to a large bin and disposing of it.

In a second video interview with police after her arrest on the murder charges in November 2011, Borowiec says she heard a noise "like a kitten" after the birth of her first child and, the following year, was aware the second child was alive as well.