When detectives tracked down Angus Sinclair there was no need to physically arrest him. He was already in prison serving a life sentence since 1982 after admitting eleven counts of raping young girls between the ages of six and fourteen. And he’d also served time for murder – more than once.In 2001, he’d finally been convicted of the 1978 murder of 17-year-old Mary Gallagher. He’d strangled her with her own clothing before raping her.However, a witness to her abduction in 1978 meant police back then had been close to identifying a suspect at the time. Some believe this close shave meant he turned his attentions to easier victims, which is why he started targeting children. Angus Sinclair had started young.He was just fifteen when he killed his first victim.Catherine Reehill was just ten years old when he lured her back to his house.Once inside, he immediately sexually assaulted her. Then he strangled her.The judge at the time warned that from reading Sinclair’s Psychiatric Reports, it was clear Sinclair would always be a danger to women.But as he was only a minor at the time, he receives just ten years and as it’s not an adult conviction, it was soon effectively lost within the system. As detectives continued questioning Sinclair, scientists continued to pursue evidence of the second killer. It was noticed that male relatives of Sinclair’s wife shared common characteristics with the suspected second killer.After eliminating all but one of her brothers, only one remained. His name was Gordon Hamilton.But, he was now dead.And his remains had been cremated.And the materials that might have identified him had since been destroyed. Despite all of those seemingly impossible obstacles, forensics once again came to the rescue.Hamilton had done some work as a handyman in a house in the mid-nineties. He’d fitted cornicing and, almost unbelievably, ten years on, when scientists removed his handiwork, they found his DNA there.And it matched their sample. “...that was the final piece of the jigsaw for the whole puzzle.” Allan Jones, Former Det. Superintendent, Lothian & Borders Police But could Hamilton and Sinclair be behind other unsolved crimes? Operation Trinity was formed to find out. They found that in 1977 Angus had been earning good money and had purchased a brand new Toyota caravanette. He said it was to go fishing. Instead, it meant that he and his brother in law, Hamilton, could serial kill across Scotland. Some even believe Sinclair could be Scotland’s worst serial killer.Similarities in the murders lead police to suspect that from 1977 to 1980, Anna Kenny, Hilda McAuley and Agnes Cooney were all victims of Sinclair and Hamilton.They had all been bound and gagged with their own clothing.But it was just that, a suspicion. All the forensic evidence that could prove their theory was gone.And with Hamilton dead, no trial could take place to prove he was the killer. Only Angus Sinclair could help and his co-operation was highly unlikely.Detective Chief Constable Tom Wood watched him in Peterhead Prison as hour after hour, Sinclair repeated, ‘No comment.’“Sinclair was a classic organised professional criminal, hard as nails, been in prison most of his life...You got no response from him whatsoever...the absolute epitome of a professional criminal.” CCTV recordings of those interviews show Sinclair sitting impassively, often totally silently. So if Sinclair wouldn’t admit his guilt, maybe a jury could be persuaded of it.