A Clark County assistant district attorney, Christopher Owens, and one of Mr. Simpson’s lawyers, Yale Galanter, pointed to different excerpts from hours of audio recordings made by various participants in the hotel room encounter to support their claims, making it clear the jury would be asked to decide what the recordings say about Mr. Simpson’s intent.

Mr. Simpson, 61, is charged with kidnapping and armed robbery. The charges stem from a confrontation in which he and five men raided a room in the Palace Station Hotel and Casino and left with hundreds of items largely related to Mr. Simpson’s football career. The material had been in the possession of two collectibles dealers, Alfred Beardsley and Bruce L. Fromong.

The dealers have insisted that the items were theirs and that they were expecting a meeting with a legitimate buyer when Mr. Simpson’s group burst in.

Four of the five men reached plea agreements and are expected to testify for the prosecution. The fifth, Clarence Stewart, is being tried with Mr. Simpson. Mr. Stewart’s lawyer, Robert Lucherini, used his opening statement to portray his client as a friend of Mr. Simpson who was unwittingly swept up in a legal and news media maelstrom and “just wants his life back.”

On one piece of the audio recordings Mr. Owens played, Mr. Simpson is heard telling another collectibles dealer, Thomas Riccio, a four-time convicted felon who set up the hotel room confrontation: “So they’re going to meet tonight, I’m going to show up with a bunch of boys and” and take back the items. He added, “They can’t do nothing about it.”

Such moments, Mr. Owens told the jury, “will show the intent, it will show the force, it will show the demands and it will show the taking of property.” He also said, “It will show the character of O. J. Simpson.”

Mr. Galanter countered that during the trial, expected to take a month, jurors would hear audio excerpts that proved Mr. Simpson thought it was appropriate for him and the men to behave as they did because the items, including several of Mr. Simpson’s championship game balls, had been stolen from him. Mr. Simpson was unaware that two of the men with him carried guns and did not see either of them brandish one, Mr. Galanter said.

“You hear him gather up these people and say, ‘Listen, I’m going to need help carrying this all out,’ and there’s talk of using a bellman,” Mr. Galanter said. “How many people commit a robbery and use a bellman? Clearly these are not the actions of someone who wants to commit a crime.”

Mr. Galanter noted that Mr. Beardsley, Mr. Fromong, Mr. Riccio and the four men who pleaded guilty had all tried to sell interviews or audio recordings of the events to the tabloid news media. Their profiteering, the lawyer said, diminishes their credibility.

Hanging over the proceedings is Mr. Simpson’s much-publicized acquittal on charges that he murdered his former wife, Nicole Brown Simpson, and her friend Ronald Goldman in 1994. A civil jury later found him liable for the deaths and ordered him to pay $33.5 million to the families of the deceased.

That judgment, of which Mr. Simpson has paid little, is one reason why the ownership of the items taken in the hotel raid is in dispute. The prosecutor, Mr. Owens, said that if Mr. Simpson had believed they belonged to him, he would have had to list them on asset forms related to the civil judgment that were filed in California in 2007. Mr. Galanter told the jury that the items Mr. Simpson wanted from the dealers included family photos that would not have been viewed as assets.