Trebeck had pleaded not guilty to her murder. Ms Jeffery, 24, is believed to have been smothered with her own jeans in the early hours of the morning after meeting Trebeck, 35, at a pub in Goondiwindi in March 2014.
Her mostly naked body was found by a fisherman the next morning.
During the course of a three-week trial, the Supreme Court in Toowoomba heard Trebeck and Ms Jeffery were seen being intimate in a park hours before her death, but she seemed happy and content.
Trebeck maintained his innocence throughout the trial and his defence sought to lay blame on another man whom Ms Jeffery met that night.
In a victim impact statement to the court, Ms Jeffery’s mother, Elena Jeffery, said she would never forget the call from police telling her that her daughter’s body had been found.
“To add insult to the pain, having the coroner tell us that he recommends that we do not view Alexis because she is unrecognisable,” she said.
“She just loved her children.
“I live with the dread of the day when Alexis’s children come and ask that question — what happened to Mummy?” Justice Glen Martin told Trebeck to take his hands out of his pockets as he was handed a life sentence.