The planned execution of a 73-year-old serial killer has been delayed after prison officials in the US state of Idaho failed to give him a lethal injection.Thomas Eugene Creech, one of the country’s longest-serving death row inmates, was imprisoned in 1974 and has been convicted of five murders in three states and suspected of more.He was serving life when he beat a fellow inmate, 22-year-old David Dale Jensen, to death in 1981 - the crime for which he was to be executed more than four decades later.