It was a despicable crime that shocked a town to its core and left a shadow hanging for more than a decade. Shirley Leach was a frail grandma who had simply nipped to the toilet before she would catch a bus.
But the 66-year-old mother-of-two would never return home. She was the victim of one of Greater Manchester's most brutal and horrific crimes.
Shirley, a widow who lived with her son in Bury, had visited her daughter at Fairfield Hospital on January 6, 1994. She caught a bus to Bury Interchange but missed the service back home.
READ MORE: The frail gran savaged by a monster in a bus station toilet: The murder of Shirley Leach 25 years on
While waiting for the next bus, she decided to use the toilet at the bus station, where she was killed. Shirley was found the next morning by a woman returning home from a night out.
She had been stripped naked, with her clothes and dentures left on the cubicle floor, and her body had been mutilated. Police began their search for the twisted killer - but there would be a long wait for justice.
Tonight (January 12), a Sky documentary will explore how Shirley's killer, former soldier and bus driver Ian O'Callaghan, was finally brought to justice. With interviews from Greater Manchester Police officers and the forensic scientist who helped solve the case, Forensics: Catching The Killer tells the story that haunted Bury for 12 years.
Andrew O'Byrne, who prosecuted Shirley's killer, told the court at the time: "Over 12 long years, Mrs Leach's killer remained a mystery. But by a combination of advances in science and a stroke of good luck, the identity of the killer was revealed.
"In the early hours of January 7 [1994], the naked body of Shirley Leach was found in a toilet cubicle at the bus station. Whilst waiting for the bus it seems Mrs Leach paid a visit to the toilet. That visit, in the end, cost her her life.
"In the cubicle she was attacked, sexually assaulted and murdered. This was a determined attack on a woman of mature years."
With never-before-seen photographs and archive footage, Forensics: Catching The Killer will show how forensic science and the police investigation were key to solving Shirley's murder and securing a successful conviction. It airs at 9pm tonight on Sky Crime, and again at 10pm on Friday, January 13.
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