Will Billy the Kid, Wild West desperado, be granted his pardon at last?

Billy the Kid, one of America's most romanticised outlaws and one of the symbols of the mythologised Wild West, could soon no longer be considered a criminal at all.

If a campaign in New Mexico succeeds on the dead cowboy's behalf, his conviction 130 years ago for murder could be overturned. Bill Richardson, the Governor of New Mexico until the end of this year, is said to be considering an appeal to grant "The Kid" the pardon he was said to have been promised during his lifetime by the then Governor Lew Wallace.

"This is something the Governor was saying he would consider pretty much since he's been in office," a spokeswoman for Mr Richardson said.

The Kid is believed to have been born Henry McCarty in 1859 – althoughhis birth could have been two years later, and he may have been called William – Billy the Kid was also known as William Bonney and Henry Antrim. Tales of his life and crimes have inspired hundreds of books, films and television series and the fact that many of the precise details of his exploits are still open to debate only adds to the legend. Today his legacy is considered the biggest tourist commodity in New Mexico, with any number of themed restaurants dedicated to his memory.

One of his earliest crimes was being arrested for stealing a bundle of laundry, when he escaped captivity by climbing up a chimney. His mother dead and rejected by his stepfather, The Kid became adept at cattle rustling in Arizona. He was forced to head back to New Mexico a wanted fugitive after apparently shooting an Irishman, Frank "Windy" Cahill, in a bar brawl.

While working as a cattle guard for the Englishman John Tunstall, he became involved in a mini-war between his boss and a rival business faction. After Tunstall was ambushed and killed, the Kid joined a group of former employees, calling themselves "The Regulators", who set out to avenge Tunstall's death.

The Regulators killed Sheriff William Brady, the man who had sent the original ambushers. The Kid became an even more wanted man than before and escaped to Texas. From there, calling himself William Bonney, he wrote to Governor Wallace asking for a pardon in exchange for testifying as a witness in another murder case. Wallace agreed, writing: "I have authority to exempt you from prosecution if you will testify to what you say you know."

The Kid testified, but no pardon was forthcoming. Despite further entreaties, the Governor reneged on his promise and ordered that he be arrested for his part in the Brady killing.

When he was found guilty, The Kid was sentenced to hang, but while in prison awaiting execution, he managed to kill both of his guards and escape. Three months later, on 13 July 1881, the law caught up with him for the last time as Sheriff Pat Garrett found him in a ranch house and shot him. At the time of his death he was thought to be aged only 21, having killed at least four and possibly nine people.

Governor Richardson, a former US Atomic Energy Secretary and one-time Democratic presidential hopeful, is known to understand the value of good publicity. In 2002, while campaigning for office, he set a world record for the most number of handshakes in an eight-hour period: 13,392.

If the pardon goes through, it would follow other recent cases where state governors have granted clemency to crimes committed by deceased celebrated figures.

Earlier this month Charlie Crist, the outgoing Governor of Florida, requested a pardon for Jim Morrison, lead singer of the band the Doors, for a 1969 conviction for exposing himself at a concert in Florida. And in 2002, George Pataki, the Governor of New York, granted a posthumous pardon to the comedian Lenny Bruce, who had been convicted in 1964 on obscenity charges.

Richardson has come in for criticism for devoting his time to considering such an odd request during his last few days in office. He is currently in North Korea for talks to try to reduce tensions in the region, and his critics also point out that he is leaving his post at a time when New Mexico is suffering from a huge economic deficit and high unemployment.

There are also questions about what the pardon would mean to the reputation of Sheriff Garrett, who caught The Kid, and who later wrote the book The Authentic Life of Billy The Kid.

Earlier this year, descendants of Garrett wrote a letter to Mr Richardson saying: "If Billy the Kid was living amongst us now, would you issue a pardon for someone who made his living as a thief and, more egregiously, who killed four law-enforcement officers and numerous others?"

But Randi McGinn, the lawyer from New Mexico who is behind the campaign to pardon The Kid, believes that the most important thing is Governor Wallace's original promise.

In her petition, she wrote: "A promise is a promise and should be enforced. It is particularly important to enforce promises and deals made by government officials, law-enforcement officers or the governor of a state made in exchange for a citizen risking his life to testify against a criminal who committed murder."