More than a decade after OJ Simpson stunned much of America by walking away from a murder trial a free man, the onetime football great known for unbridled speed was preparing to spend in prison what should have been the prime years of a superstar's retirement.

The 61-year-old former athlete, Hollywood actor and pioneering symbol of African-American celebrity success was sentenced on Friday to as much as 33 years behind bars, with eligibility for parole after nine, for a robbery caper in Las Vegas last year.

As the retired football hero once known as 'The Juice' was led away in shackles, many who have followed his downward spiral over the years still wondered how a figure who inspired a generation could have fallen so far from grace.

Even Simpson's former sister-in-law, Denise Brown, who believes he was guilty of murdering her sister, lamented his fate.

'It is very sad to think that an individual who had it all, an amazing career, beautiful wife and two precious children has ended up like this,' Denise Brown said in a statement following the sentencing.

The case stemmed from a bid by Simpson to reclaim what he insisted were personal possessions that had been stolen from him.

With five other men in tow, he stormed into a small room at the Palace Station hotel and casino in September 2007 and made off with thousands of dollars in collectibles they seized at gunpoint from a pair of memorabilia dealers there.

In the words of Simpson himself, pleading for leniency in a hoarse, trembling voice as he stood before the judge in blue jail garb: 'In no way did I mean to hurt anybody, to steal anything.'

But Clark County District Court Judge Jackie Glass rejected defence arguments that Simpson acted without criminal intent and she suggested that he was his own worst enemy.

'While at this case bail hearing, I said to Mr. Simpson that I didn't know if he was arrogant or ignorant or both. Then during the trial and through this proceeding, I got the answer: it was both.'

It was a stinging, final rebuke for a man who has lived largely as a public pariah, years after his towering athletic achievements led to television and film acting, including rental car ads in which he dashed through a crowded airport in a business suit, ever the football running back.

Blazing a trail later followed by the likes of basketball greats Michael Jordan and Ervin 'Magic' Johnson, Simpson was one of the first black athletes to parlay his sports success into a career as a major celebrity pitchman and pop culture superstar.

His sentencing came two months after a Las Vegas jury concluded a three-week trial by finding Simpson and co-defendant Clarence 'CJ' Stewart guilty of all 12 charges against them, including kidnapping, assault, robbery and assault with a deadly weapon.

Simpson's conviction came 13 years to the day that he was acquitted in Los Angeles of the murder of his ex-wife, Nicole Brown Simpson, and her friend, Ron Goldman, who were stabbed and slashed to death in June 1994.

A civil court jury later found Simpson liable for the deaths and awarded $33.5 million in damages to the victims' families, a judgment that remains largely unpaid.

Both prosecutors and defence lawyers said the case was inextricably linked with his previous legal woes. Prosecutors contended the robbery grew out of grudges Simpson had nursed since his murder trial and civil case.

Simpson's lead attorney, Yale Galanter, has said his client's past as a notorious murder defendant, widely seen as having eluded justice in Los Angeles, was a factor in Las Vegas jurors' guilty verdict.

But even as his client faces years in prison, Galanter said that Simpson might have lucked out once again.

'I think he is a little relieved that he didn't get a life sentence,' Ga