The execution by lethal injection of an inmate in the US state of Tennessee has been halted after medical staff were unable to tap a vein, officials say.WARNING: This story contains details viewers may find distressing.Tony Carruthers, 57, was scheduled to be put to death at a prison in Nashville on Thursday, local time, after he was found guilty of kidnapping and murdering three people in 1994.The Tennessee Department of Corrections said medical personnel established a primary IV line to deliver the lethal drugs but could not find a suitable vein for a backup line."The execution was then called off," the department said in a statement.Maria DeLiberato, an American Civil Liberties Union (ACLU) attorney representing Carruthers, said she saw him "wincing and groaning" while officials attempted to find a vein, calling it "horrible" to watch.Maria DeLiberato said the execution was called off because a suitable vein could not found. (AP: Mark Humphrey)Ms DeLiberato said that after establishing an IV line in Carruthers's right arm, medical personnel tried his other arm, his left hand and his left foot before trying to establish a central line.Unable to establish a central line, the medical team accessed a vein in his right shoulder before the warden received a phone call and announced the execution was off, she said.Tennessee Governor Bill Lee granted Carruthers, who has maintained his innocence, a one-year reprieve from execution.Stacy Rector, the executive director of Tennesseans for Alternatives to the Death Penalty (TADP), said the "botched execution attempt of Tony Carruthers is horrifying but not surprising"."TADP has sounded the alarm for years about the serious problems with lethal injection and urged our state toward greater transparency so these problems can be addressed," Ms Rector said.Carruthers convicted of killing three peopleCarruthers was found guilty of the 1994 kidnappings and murders of Marcellos Anderson, his mother Delois Anderson, and Frederick Tucker.Authorities said Marcellos Anderson was a drug dealer and that Carruthers was trying to take over the illegal trade in their Memphis neighbourhood.Carruthers was forced to represent himself at trial after repeatedly complaining about court-appointed attorneys and threatening to harm several of them.There was no physical evidence tying Carruthers to the killings, and he was convicted primarily on the basis of testimony from people who said they had heard him confess to or discuss the crimes.The ACLU said it would continue to push for DNA testing on evidence in the case, saying it should have been done long ago.Carruthers's attorneys have also argued that he has mental health issues that mean he should not be executed.Execution numbers on the rise in USCarruthers was one of two inmates scheduled to be executed in the United States on Thursday.Richard Knight, 47, was executed by lethal injection in Florida for the murders of a woman and her four-year-old daughter in 2000.Across the United States, 13 executions have been carried out this year: six in Florida, four in Texas, two in Oklahoma and one in Arizona.There were 47 executions in the country last year, the most since 2009, when 52 people were put to death.Florida carried out the most executions in 2025, with 19, followed by Alabama, South Carolina and Texas, where there were five each.Thirty-nine of last year's executions were carried out by lethal injection.Three were by firing squad and five by nitrogen hypoxia, which involves pumping nitrogen gas into a face mask, causing the prisoner to suffocate.The use of nitrogen gas as a method of capital punishment has been denounced by United Nations experts as cruel and inhumane.The death penalty has been abolished in 23 of the 50 US states, while three others — California, Oregon and Pennsylvania — have moratoriums in place.US President Donald Trump is a proponent of capital punishment and has called for an expansion of its use "for the vilest crimes".The Department of Justice said in April that it was seeking to expand the use of the death penalty in federal capital cases and add the firing squad, electrocution and gas as methods of execution.AFP/AP