ST. THOMAS, Ont. -- A couple whose depraved sexual appetites led them to brutally murder and rape an Ontario teacher they picked up on the side of the road three years ago apologized to the woman's grief-stricken family Thursday as they prepared to spend the rest of their lives behind bars.

Tanya Bogdanovich, 34, and Michael MacGregor, 22, chose to face Noelle Paquette's family and friends in a packed St. Thomas courtroom as they took turns voicing their remorse for the gruesome killing that sent shockwaves through southwestern Ontario.

Though both said they wished they could reverse their actions and bring Paquette back to life, neither shed light on what fuelled their violent plan -- a plot that initially focused on a teenage girl but shifted to the Sarnia teacher by a twist of circumstance.

Nor did they ask for forgiveness.

"I want to say sorry, I know I can't change or take back what I've done no matter how much I wish I could," said MacGregor, who addressed the court first. "What I did was terrible and because of it Noelle is gone, when instead she should still be with you."

"I'm not asking for your forgiveness -- I don't deserve it and could never hope for it," he said.

Bogdanovich's voice broke as she acknowledged the "all-encompassing pain" caused by Paquette's murder, which she described as a "horrendous tragedy."

"One night forever changed the course of many lives and it can never be undone," she said, adding she regretted waiting so long to plead guilty.

At least one member of Paquette's family left the courtroom while Bogdanovich spoke. Others looked down and wiped tears from their eyes.

Bogdanovich and MacGregor pleaded guilty late last year to first-degree murder in the savage slaying of Paquette, a stranger they abducted on a road as she was walking home from a New Year's Eve party.

The offence carries an automatic life sentence with no chance of parole for 25 years. The pair must also be added to the DNA bank and sex offender registry and face a lifetime firearms ban. They must also refrain from contacting Paquette's family and friends.

In handing down the automatic sentence -- the most strict available under law -- Ontario Superior Court Judge Bruce Thomas said the pair's "vile and despicable" actions required them to be removed from society for most of their lives.

He noted, however, that no sentence could ease the ache of loss and stressed that Paquette's family should in no way wonder if they could have saved her from her tragic fate.

"There was no blame for any of you here," he said. "The responsibility, all of it, lies with the two people in the prisoners' boxes."

Paquette's father, Roger Paquette, said outside court that the sentence was "neither an ending nor a beginning."

"It is a message to everyone to be cautious but not afraid, to live life to the fullest and to love and be kind," he said. "Our memories of our daughter Noelle have given us the courage to live on."

Paquette was "merely in the wrong place at the wrong time," and though she tried to fight off her attackers, she was overwhelmed by their "violent sexually motivated desires," according to an agreed statement of fact read in court Wednesday.

Court heard Bogdanovich, a nurse and mother of three who was already in a relationship, met MacGregor on a social networking site for people interested in BDSM, fetishism and kink in June 2012.

Over their seven-month relationship, the couple developed increasingly savage sexual tastes, court heard.

The pair chronicled their sexual desires and activities in pictures, videos and writings and by September of that year, were discussing their fantasy of abducting and raping a teenage girl. The statement said the couple's plan fell through when their chosen target was unavailable and they decided to pick up a "random" instead.

Paquette had gone to a party with her boyfriend but stormed out after they got into a fight, court heard. She tried unsuccessfully to get a taxi and decided to walk home.

She last texted her boyfriend around 2:30 a.m., just moments before she was abducted, the statement said.

Her body was found in a woodlot on Jan. 2, 2013, less than 24 hours after she was reported missing by concerned family and friends.

An autopsy found Paquette died from the dozens of stabbing and incised wounds that perforated her heart, lungs, liver and other organs and slashed her throat.

"It was determined that she was still alive when she sustained these injuries but would have succumbed rapidly due to their severity," court heard.

Police found Bogdanovich and MacGregor by the side of the road on New Year's Day after their car broke down not far from the site of the killing.

At the time, Paquette had not been reported missing and there was no reason to suspect the couple, court heard.

Suspicion quickly turned their way once her body was found and the pair started planning their escape, only to be arrested a day later.

Lawyers for Bogdanovich and MacGregor said it's unclear what motivated their clients and that both intend to seek psychological help while in prison.

Natasha Calvinho said at sentencing that Bogdanovich had an emotionally difficult childhood that saw her placed in foster care and sexually abused -- trauma for which she never received treatment.

Bogdanovich's boyfriend, from whom she hid her relationship with MacGregor, continues to support her, Calvinho said, but "her children are going to have to grow up knowing what mom has done."