Long-lost video showing Martin Luther King's killer in police custody has been posted online, 45 years to the day after the civil rights leader's murder, BBC News reported.

Officials in Tennessee unearthed the tapes of James Earl Ray in 2011 but had no way to view the old technology.

Ray is seen in 1968 on a plane after extradition from Britain and as he is searched and given a medical exam and a bulletproof vest at a Memphis jail.

King, a Baptist minister, was shot in Memphis on 4 April 1968, at age 39. Ray, a racist drifter and bungling career criminal, was captured in London by Scotland Yard detectives two months later.

Extradited to Memphis, he avoided a jury trial - and possibly the electric chair - by entering a guilty plea the following year.

He was sentenced to 99 years in prison. He later recanted his confession, saying he had been framed by shadowy conspirators, but his plea was repeatedly upheld in the courts. He died in 1998 at 70.

The footage of Ray in custody was discovered in the Shelby County sheriff's office along with logs and photographs from the investigation.