A selfie helped convict a killer who strangled her best friend to death - because it shows her wearing the belt she used in the deadly attack.

Brittney Gargol, 18, was strangled to death by Cheyenne Rose Antoine, 21, in Saskatoon, Saskatchewan, Canada in March, 2015.

Antoine has now been found guilty of manslaughter thanks to the image of the pair together.

The teenager's body was found dumped by a road south of Saskatoon with a belt discovered nearby, the Daily Mail reported.

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A photo of Gargol and Antoine - her best friend - had been posted to Facebook six hour before the body was discovered.

The photo shows Antoine wearing a belt that matched the one found near the body, The Star Phoenix reports.

Antoine also posted on Gargol's Facebook, writing 'Where are you? Haven't heard from you. Hope you made it home safe,' in an alleged attempt to cover her tracks.

Antoine initially told police that the pair had been out drinking on the eve of Gargol's death but that she had gone home with an unknown man at the end of the night and did not know what had happened to her friend.

However, police later received a tip-off that Antoine had made a drunken confession to the killing, CBC reports.

Antoine later admitted to the court that the pair had gotten into an argument, but that she does not remember killing Gargol.

She pleaded guilty to manslaughter and was sentenced to seven years in prison on Monday.

In a statement released through her legal representative, Antoine said: 'I will never forgive myself.

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