How this Facebook selfie led a woman to be convicted of killing her best friend.

It was meant to be just a normal night out for best friends Cheyenne Rose Antoine and Brittney Gargol.

The duo posed for selfies before heading out for a night of drinking near Saskatoon in Canada. That was March 25, 2015.

Almost three years later, and 21-year-old Cheyenne has this week been found guilty of her best friend’s manslaughter and has been sentenced to seven years behind bars.

Eighteen-year-old Brittney’s body was found unresponsive on the side of the road, on the outskirts of the Canadian town. According to CBC News, the man who found Brittney said she was “cold to the touch”. Police determined she had been strangled to death with a belt found near the body.

During their investigations, police discovered a selfie the pair had posted online in the hours before Brittney’s death. In the photo, Cheyenne was wearing the belt that had been used to kill the teen.

Cheyenne had initially tried to throw officers off her scent in the days and months after her best friend's death. Just hours after Brittney was killed, she posted on Facebook asking where her friend was.

She told police that she and Brittney had visited several bars during their night, and that her friend had left with an unknown man.

She even shared a touching tribute to her friend on the very same photo that would lead to her conviction.

"I miss you soo much...wish heaven had visiting hours so I could come see you," she wrote.

"I'm blessed to have met you & have you be apart of my life, Still can't believe those last two days were going to be the last 2 days i got to be able to hug you, talk to you & laugh with you.

"You were way to young to go, gone but never forgotten."

Her lies were soon uncovered when security footage showed the duo had never reached the bar Cheyenne had told them about.

A witness then came forward and revealed that Cheyenne had confessed to hitting and strangling her friend after they got into an argument.

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After a nearly two year investigation, Cheyenne was initially charged with second-degree murder and pleaded guilty to manslaughter. She said she doesn't remember killing her friend, but doesn't dispute that it happened.

"I will never forgive myself," a statement issued through Cheyenne's lawyer, Lisa Watson, said.

"Nothing I say or do will ever bring her back. I am very, very sorry... It shouldn't have ever happened."

The case of Cheyenne and Brittney isn't the first where social media has been used as a valuable crime-fighting tool.

Police regularly share images of wanted criminals online in the hopes that people seeing and sharing the pictures will bring them closer to arrest.

In August last year, Crime Stoppers released a list of Australia's 20 most wanted criminals. Just three days after revealing the list, nine had been arrested.

Just a month earlier, a Canadian man was arrested in Texas over the murder of his girlfriend after he posted a chilling 'confession' on Reddit.

In 2016, police were able to link a Sydney man to a murder after they found ominous Facebook status updates on his profile.

And it's not just social media that's helping catch criminals out: Connecticut man Richard Dabate was charged with the murder of his wife after data from her Fitbit proved she was walking around an hour after he told police she had been shot and killed by a masked intruder.