Cutting deals with co-defendants to testify against O.J. Simpson could undercut prosecutors if they ever need to convince a jury the former football star is guilty of serious crimes, legal experts said Monday.

But that could happen only if the case makes it past a preliminary hearing next week before a judge whose main concern will be what the evidence is rather than where it came from. Of the five men charged with Simpson in a hotel-room confrontation with sports memorabilia dealers, three have agreed to plead guilty and testify against him.

"This is a basic prosecution tactic that is very effective," said Jody Armour, a criminal law professor at the University of Southern California. "Its greatest weakness is that the jury is going to hear from the defense that the only reason they're testifying is because they cut a deal that can benefit them."

Simpson co-defendant Michael McClinton told a judge Monday that he will plead guilty Nov. 13 to robbery and conspiracy to commit robbery. The 49-year-old Las Vegas man could end up being the star witness.

McClinton's lawyer, William Terry, said he can testify that Simpson asked him to bring guns to a room at a Las Vegas casino hotel to get items that Simpson said was his. That would contradict Simpson's claim that no guns were involved.

McClinton wielded a gun and acted like a police officer Sept. 13 when Simpson and the others allegedly robbed collectibles dealers Bruce Fromong and Alfred Beardsley, according to police reports. McClinton's lawyer said his client worked as a security guard and had a concealed weapons permit.

Authorities say memorabilia taken included football game balls signed by Simpson, Joe Montana lithographs, baseballs autographed by Pete Rose and Duke Snider, photos of Simpson with the Heisman Trophy, and framed awards and plaques, together valued at as much as $100,000 (euro69,488), according to police reports.

New York defense lawyer Michael Shapiro called prosecution offers of plea deals and immunity "a standard way of building your case."

"Ultimately, it will come down to whether a jury will believe witnesses who have cut deals to testify," said Shapiro, who provided television commentary during the trial in which Simpson was acquitted of murder in the 1994 slayings of his wife, Nicole Brown Simpson, and her friend, Ronald Goldman.

McClinton's agreement to enter a plea was not a surprise, said Simpson lawyer Yale Galanter, who said he believed McClinton will be the final cooperating witness.

Walter Alexander, 46, a Simpson golfing buddy from Mesa, Arizona, has pleaded guilty to conspiracy to commit robbery, and Charles Cashmore, 40, a union laborer from Las Vegas, has pleaded guilty to felony accessory to robbery.

"What this comes down to is the real bad guys are pointing a finger at O.J., and the prosecution is giving away the courthouse to try to shore up their case," Galanter told The Associated Press. "We look forward to cross-examining these witnesses."

Simpson and co-defendants Clarence Stewart and Charles Ehrlich each face 12 criminal charges in the preliminary hearing beginning Nov. 8, including kidnapping, armed robbery, assault with a deadly weapon, conspiracy and coercion. A kidnapping conviction alone could result in a sentence of life in prison with parole.

McClinton could get no more than 11 years in prison under his plea deal; Alexander faces six years at most and Cashmore five years. All could receive probation after testifying.

Tom Pitaro, a Las Vegas defense lawyer who teaches trial advocacy at the Boyd School of Law at the University of Nevada, Las Vegas, called the disparity a possible problem for prosecutors.

"Sometimes, this has an effect where the jury can say they don't think prosecutors are treating this guy fair by charging him with all these offenses while these other guys got less," Pitaro said.

Lawyers for Stewart and Ehrlich did not respond Monday to messages seeking comment.

With testimony from McClinton, prosecutors can rely on accounts from six of the nine people who were in the hotel room during the encounter, including the two alleged victims, a California collectibles broker who arranged the ill-fated meeting, and the three former co-defendants.

Armour said that if the case goes to trial, defense lawyers will emphasize the checkered histories of the participants. Of the eight men who were in the room with Simpson, six have run afoul of the law before, with convictions for domestic violence, theft, trafficking cocaine, stalking, assault with a deadly weapon, grand larceny and arson among them.