A Scottish truck driver previously convicted of murdering three girls was found guilty Thursday of raping and killing a 9-year-old in Northern Ireland in 1981.Robert Black was immediately given a fourth life sentence for the murder of Jennifer Cardy, the Belfast Telegraph reported. The judge in Antrim Crown Court then ordered him taken to the cells.The jury deliberated for less than 5 hours after a trial that took more than five weeks. Black was stone-faced as the verdict was read, while Jennifer\'s mother cried quietly.Black, 64, has been in custody since 1990 when police in the village of Stow in Scotland discovered a 6-year-old girl tied up and gagged in the back of his van. He was convicted of killing two girls in Scotland -- Susan Maxwell, 11, from the Borders area, and Caroline Hogg, 5, from Edinburgh -- and one in England, Sarah Harper, 10, of Nottingham.Jennifer, who lived in Ballinderry in County Antrim, vanished as she cycled to a friend\'s house. Her body was found six days later about 15 miles away.The evidence at the trial included a credit card receipt from a gas station in Coventry investigators found amid millions of old Shell Oil records. Prosecutors used that to show Black, a dispatch driver based in London in 1981, was headed south the day after Jennifer was killed at the wheel of a van that had been in Northern Ireland.