Los Angeles  - Prosecutors will ask a judge on Friday to sentence former American football star OJ Simpson to 18 years in prison for his part in an armed robbery and kidnapping case last year in Las Vegas, according to court papers released Wednesday.

Simpson, 61, was found guilty in October on 12 charges stemming from the incident in which he and his cohorts used guns to force two sports memorabilia dealers to hand over a number of items that Simpson believed had been stolen from him.

In pre-sentencing papers, Simpson attorney Gabriel Grasso argued that Simpson should receive the minimum sentence of six years in prison. Prosecutors asked for 18 years.

The judge could also impose the maximum life sentence on the celebrity, who was controversially acquitted of the 1994 murders of ex-wife Nicole Brown Simpson and her friend, Ronald Goldman.

Simpson has been held in isolation in jail since his October conviction. Because of his celebrity, he will remain in solitary confinement during his prison term.

Lawyers for Simpson are planning to appeal his conviction, claiming that the jury was unduly influenced by the previous case. In arguing for the minimum sentence, Simpson's legal team pointed to his lack of prior criminal convictions. They admitted that his judgement in the incident was faulty but pointed out that no one was hurt and claimed extenuating circumstances.

"These were not crimes committed on strangers but were acts stemming from prior relationships with the individuals in the room at the Palace Station," Grasso wrote in the memorandum. "There is nothing in the record to show that Simpson evinced a criminal mind or showed the requisite criminal intent."

The case revolved around an incident in September 2007, when Simpson traveled from his Florida home to Las Vegas for a friend's wedding. While there, he heard that memorabilia dealers were trying to sell items from his football career, and Simpson organized a group of friends to try to retrieve the goods.

In the case, jurors heard evidence that Simpson's gang burst into the dealers' hotel room, threatened them with guns and prevented them from leaving until they returned the items in question.

Simpson was arrested the day after the incident by Las Vegas police. (dpa)