His was a lonely death by garrotte, an iron collar which is slowly tightened around the victim's neck until they are strangled.
Salvador Puig Antich, an anarchist mixed up in a robbery in which a police officer was killed, became the last person to be executed under General Francisco Franco's dictatorship.
He was the scapegoat of a regime which was determined to prove its authority after the Basque separatists Eta assassinated the prime minister, Luis Carrero Blanco, in an audacious attack weeks before.
But Puig Antich's death in 1974 became a symbol of rebellion for a country which had endured 35 years of "El Caudillo".
Now, more than 30 years after his death, Puig Antich's case has become a cause célèbre. His family and a team of lawyers have fought for three decades to prove he was denied justice by a kangaroo court. Spain's Supreme Court is considering reopening a case which has refused to go away, despite the best efforts of not only Franco, but subsequent military authorities.
And a new film, starring Daniel Brühl and Leonor Watling, will highlight the fate of an unwilling martyr. Salvador, which will be released in Spain on 15 September, tells the story of this 25-year-old idealist who believed in "making a difference". Brühl, star of Good Bye Lenin!, plays Puig Antich, the handsome, though naive revolutionary.
Watling, who appeared most recently in The Secret Life of Words, plays Puig Antich's girlfriend.
The film's executive producer, Jaume Roures, said: "Salvador became a hero, a symbol of rebellion. With the film we wanted to show who that middle-class, attractive and intelligent young man was and how a brutal regime sentenced him in a trial in which his rights were not respected."
Puig Antich came from a well-to-do Barcelona family which made its money from a chemicals warehouse. His father, Joaquim Puig Antich, had been a political activist and was condemned to death but then pardoned. Puig Antich's sister, Imma, said: "My father was afraid something would would happen to us. But we were anti-Franco and we wanted to do something to fight the regime."
Puig Antich joined the Iberian Liberation Movement (MIL), an anarchist organisation which believed in robbing banks to finance its cause. After a series of heists, police mounted a special operation to crack MIL. The film begins with MIL's last bank robbery in September 1973.
Four members had earlier been arrested and, under torture, one revealed when the robbery was due to take place. A special police plain clothes unit set up an ambush. A struggle started in which a gunshot rang out and everyone froze.
One police officer, Deputy Inspector Anguas, was shot and later died in hospital.
One MIL member, Xavier Garriga, was tortured in prison until he signed a statement saying Puig Antich had fired the gun which killed the policeman. But Puig Antich's family and lawyers claim his guilt cannot be established because crucial evidence was not admitted to court.
Garriga was not allowed to testify. Puig Antich told the court he pulled out a gun and shot it "a couple of times, without aiming it or trying to hurt anyone". One officer claimed that Puig Antich shot at Anguas.
Dr Ramon Barjau, who examined the dead officer, said there were two bullet wounds on his leg and groin and signed the death certificate. But his evidence was not accepted by the military court.
Earlier this year, Dr Barjau told the Supreme Court he would stand by his statement, saying the officer's body was "ridden with bullets". But in the original trial, a post-mortem examination which said the officer had three bullet wounds was the only one admitted. Sebastian Martínez Ramos, a lawyer in the case, said the bullets found in the bodies of Puig Antich and Anguas disappeared and were never presented to the judge. Mr Martinez Ramos has used new technology which tracks bullet paths in 3D to help analyse the evidence.
He believes that it may prompt the Supreme Court to reopen the case, despite a series of failed attempts.
Puig Antich was convicted in a one-day trial and condemned to death for killing a public servant "for political reasons".
Eighteen days earlier, Eta killed Franco's nominated successor Carrero Blanco in a car bomb in Madrid. In the film, Puig Antich says: "That bomb has also killed me."
Imma Puig said: "Salvador insisted that he didn't want to be a martyr for any cause." His other sister, Carmen, added: "Our wounds are still open and will be until the case is reopened and justice is done."