TORONTO – The first-degree murder conviction handed to a man who beat, strangled and mutilated a young woman before dumping her near-naked body on a trail 11 years ago was upheld Monday.In its ruling, the Ontario Court of Appeal rejected arguments from Roy Niemi that his trial judge had made errors related to the “Mr. Big” sting that snared him, and that he did not sexually assault the victim because she was already dead when sexual activity occurred.A jury convicted Niemi, of Orillia, Ont., in January 2013 in the death of Alyssa Watson, 20. A woman walking her dog along an unused railway line in the city in August 2006 discovered the remains.While Niemi was the last person to have seen Watson alive, according to court records, the critical evidence against him came from a Mr. Big operation in which undercover officers pretending to be criminals gained his confidence and pumped him for information on the killing.On appeal, Niemi argued Superior Court Justice Cary Boswell should not have allowed the jury to hear that evidence but the higher court disagreed. Boswell would have been right to allow the confessions from the sting even under stricter Mr. Big rules put in place after the conviction, especially given that the suspect was not vulnerable and the undercover officers did nothing wrong.The Appeal Court also said the evidentiary value of his confessions overwhelmed the risk of prejudice to him.“His statements to Mr. Big operatives contain a raft of unpublicized and impressive detail, stamping them as reliable in spite of the non-coercive inducements that were used to encourage Mr. Niemi to admit the crime,” the Appeal Court said. “Those statements were hauntingly accurate regarding unpublicized details surrounding the killing.”Court records show Niemi and Watson met the evening before her body was found, making him immediately a prime suspect. However, police had difficulty tying him to the crime. They set up a Mr. Big operation in which an undercover officer befriended Niemi but he failed to confess to the killing and the sting was abandoned.A year later, however, investigators tried again. This time, two purported gangsters played the Mr. Big role. In late 2008, Niemi, whose money situation had worsened after losing his babysitting job, made a series of incriminating statements.Among other things, he told the undercover officers he had hit Watson on the head with a whisky bottle, then used her purse strap to strangle her. He also said someone had paid him $10,000 to kill her because she had stolen cocaine.Niemi did deny the killing was sexually driven — the basis for the first-degree murder conviction — saying he only removed Watson’s clothes and slashed her breast after he had killed her as a way to mislead police.Because she was already dead, he argued, he could not have sexually assaulted her. However, the Appeal Court dismissed Niemi’s argument on that score.It would be difficult to accept the notion that an attacker who uses force to render a victim compliant could escape a first-degree murder conviction because the person died before a sexual assault could took place, the court said.“There was ample evidence to permit a jury to infer that the entire attack was sexually motivated or sexual in nature, making the killing first degree murder,” the Appeal Court ruled.