Utah banned execution by firing squad in 2004, retaining lethal injection as the default method for carrying out death sentences.
But because he was convicted prior to that date Gardner retained the right under previous state laws to choose between lethal injection or firing squad as his method of execution.
Gardner was strapped into a chair with a target pinned over his chest as five anonymous marksmen armed with .30-calibre rifles fired from behind a wall.
|The execution has been condemned as barbaric and archaic [EPA]
Prison officials said that four of the guns were loaded with live rounds, while one was loaded with a blank so that the shooters would never know for sure if they fired a fatal round.
Gardner's execution makes him the third man killed by firing squad in the US since a Supreme Court ruling reinstated capital punishment in 1976.
The most famous case was the 1976 execution of Gary Gilmore, who gained notoriety for demanding that his execution be carried out and whose last words were simply "let's do it".
Gardner's attorney said his client's decision to opt for the firing squad was based on preference, not a desire to embarrass the state or draw publicity to his case.
Critics have condemned the method of execution as barbaric, archaic and reminiscent of "Wild West" style justice.
Others have said the dramatic method of execution plays into the hands of criminals who seek to die in a "blaze of glory".
On Thursday the American Civil Liberties Union denounced Gardner's imminent execution as an example of what it called the United States' "barbaric, arbitrary and bankrupting practise of capital punishment."
|Five gunmen fired through slits in a wall on the death chamber [EPA]
Meanwhile at an interfaith vigil in Salt Lake City on Thursday evening, religious leaders called for an end to the death penalty.
"Murdering the murderer doesn't create justice or settle any score," said Rev. Tom Goldsmith of the First Unitarian Church.
Deborah Denno, professor of law at Fordham University in the US, told Al Jazeera the case had reignited the political debate on capital punishment, with some arguing that while it may seem brutal, use of the firing squad may actually be more humane than other options.
"Lethal injection started to be used in the United States in 1982. Consistently over the decades it's been shown to have vast numbers of problems, in the way that the firing squad never has," she said.
"For the observers lethal injection looks much better, it looks like the inmate is simply going to sleep. Those who have observed a firing squad execution report being more disturbed."
Denno said many of those states that retained the death penalty were choosing lethal injection "because it's better for the witnesses, but it's actually worse for the inmate".
"I think execution methods in general, in addition to finding that inmates have been innocent after being executed - bit by bit this is wearing down the death penalty in the United States," she said.