David Boyd found guilty of 1992 murder of seven-year-old Nikki Allan

Scientific breakthroughs allowed experts to detect DNA from Boyd, who was 25 at time of killing

A child killer who evaded justice for more than 30 years has been found guilty of murder.

David Boyd took seven-year-old Nikki Allen to an abandoned building where he beat her with a brick and repeatedly stabbed her to death in 1992.