A man murdered two Mormon missionaries because he believed their church had ignored him while he was in jail.
The claim was made by a lawyer for the United States Government at a hearing considering whether Dr Robert Elmer Kleason, 69, should face a double murder trial.
The US Government has issued an extradition warrant claiming that Kleason, formerly of Barton-upon-Humber, Lincolnshire, murdered two Mormon church workers in Travis County in October 1974.
Kleason had been found guilty of murdering one of the men, 19-year-old Mark Fischer, and spent two-and-a-half years on death row in Texas before his conviction was quashed.
He was released from jail, then moved to Britain in 1990.
But American authorities now seek his extradition to face a re-trial as they say they have fresh evidence linking him to the murder of Mr Fischer and of 20-year-old fellow missionary Gary Darley.
Kleason knew the two missionaries, who were from the Church of Jesus Christ of Latter-Day Saints - the Mormons.
They disappeared after going to Kleason's trailer to eat venison he had invited them to share, Mr James Lewis, for the United States Government, told a hearing at Bow Street Magistrates' Court in central London.
No trace had been found of the bodies of the two young men, he said.
The new evidence includes that produced by DNA techniques used to analyse blood-stained trousers owned by Kleason.