Christopher Watcheston, seen in January 2008, faces a prison sentence with no chance of parole for 25 years. (CBC)

A Calgary man has been convicted of first-degree murder in the sex assault and slaying of a mother of five near a C-Train station.

Christopher Watcheston, 24, followed Arcelie Laoagan, 41, from the Franklin LRT station in January 2008 to a pathway where he raped and killed her.

Court of Queen's Bench Justice Kristine Eidsvik rejected Watcheston's claim that he didn't intend to kill Laoagan, and his assertion that he kicked her in the head in an attempt to cause amnesia. Watcheston's lawyer had argued for a lesser conviction of second-degree murder.

In an 80-minute decision Tuesday, the judge said she couldn't believe key parts of Watcheston's testimony, describing it as filling in the gaps of what he could remember and reconstructing the rest.

Eidsvik referred to chilling surveillance video entered during the trial that showed Watcheston stalking Laoagan out of the station. She said Watcheston wasn't as impaired as he claimed to be, with the images proving he was walking, climbing stairs and asking and following directions without much difficulty.

Arcelie Laoagan is seen leaving the Franklin LRT station with Christopher Watcheston close behind her in video evidence entered during the trial.

The judge ruled that Watcheston maintained his illegal domination over his victim during the sex assault that was followed by the killing, thus meeting the Criminal Code definition of first-degree murder.

The conviction carries a sentence of life in prison with no chance of parole for at least 25 years.

During the judge-only trial, Watcheston testified that he was drunk and high on the hallucinogenic herb, salvia, when he mistook Laoagan for his own mother and followed her.

He said he was high and feeling "out of his own body" during the sex attack, but a drug expert refuted that, saying salvia's effects would have worn off by then.

As Laoagan tried to call on her cellphone for help, Watcheston said he kicked her at least four times with his steel-toed work boots.

Killer exploded after victim fought back

Witnesses, including a psychologist and a nurse, told the court that Watcheston's testimony contradicted what he said in previous interviews, including the amount of alcohol and drugs he consumed, and how Laoagan reacted during the attack.

The judge said Tuesday she believes Watcheston and Laoagan fought along the secluded pathway because the victim's clothing was found away from her battered body.

Arcelie Laoagan worked two jobs in the hopes of sponsoring her her husband and five sons to Canada from the Philippines. (CBC)

Eidsvik said she believes that after being punched, Laoagan pushed Watcheston back, causing him to fall. The judge said the killer then "got angry and exploded."

Watcheston sat in the prisoner's box with his back to the crowded gallery during the judge's decision.

Laoagan was returning home from a printing company, one of the two jobs she worked, on the night she was killed. She had a commerce degree and was upgrading her skills to work as an accountant in Canada.

She was also in the middle of applying to sponsor her husband and five sons to join her in Canada from the Philippines.

Felix Guerrero, acting Filipino honorary consul general in Calgary, said the application has since been denied but could still be reopened.

"There's some things that we have to work on and some things we have to iron out, but hopefully in the near future they will be here and realize the dream Arcelie had for her family," he told reporters on Tuesday.

"I'd like to thank … Calgarians for the support and this gave us closure to the case," said Laoagan's sister, Marlyn Hori. "We're satisfied with the verdict. Justice has been served."

Watcheston's own mother was murdered

Crown prosecutor Gordon Wong acknowledged the case gripped the city not only because of the reaction it created for people's own personal safety, but also due to the kind of person the victim was.

"Much of it had to do with who Arcelie was: hard-working individual, five kids, trying to make a better life for herself in Canada. Basically, a victim at random and a brutal killing. So I think it's her in particular that makes it that riveting, I think, for people," said Wong.

In her decision, the judge touched on Watcheston's own troubled life: His mother was stabbed to death in Regina when he was 14.

"He fell through the cracks of life. He fell through every crack the system is designed for. His troubled youth is an understatement in terms of his background, the life he led, his mother murdered behind a hotel in Saskatchewan," said Alain Hepner, Watcheston's lawyer. "And it just unravelled after that."

With files from Bryan Labby