LAS VEGAS, Nevada — One of the first police officers to respond to the alleged sports memorabilia robbery last year in a Las Vegas hotel took the stand Wednesday afternoon in the third day of O.J. Simpson’s high-profile jury trial.

Detective Andy Caldwell of the Las Vegas Metropolitan Police Department testified when the call came in that a robbery had taken place at the off-Strip hotel — a robbery involving NFL Hall of Famer O.J. Simpson — his first thought was, “It couldn’t be true.”

Simpson and his co-defendant, former golfing buddy, Clarence “C.J.” Stewart, both face a dozen robbery, weapons and kidnapping-related offenses following a run-in with two memorabilia dealers, Alfred Beardsley and Bruce Fromong, Sept. 13, 2007, at the Palace Station Hotel & Casino.

Caldwell, the first police officer to testify in the trial, described for the court the bizarre scene he and his partner, Edward LaNeve, encountered when they made their way to the hotel room where the incident occurred.

That’s where the two officers found three memorabilia dealers: two men who said they were robbed at gunpoint, Bruce Fromong and Alfred Beardsley, and a third man, Thomas Riccio.

“They seemed to have been upset with Mr. Simpson, but I think the primary concern at the time was the fact they (allegedly just) had guns pointed at them,” Caldwell testified.

Caldwell said he then questioned Riccio, who he remembered as “a very hard person to interview.”

“(Riccio) was very interested in telling me a long, drawn-out story,” Caldwell said. “He was not following the direction of my interview.”

Because the two were “butting heads,” Caldwell said he cut his interview with Riccio short, leaving another officer to complete it.

During his statements to police, Riccio never mentioned that he had recorded the audio of the events that had just taken place – nor that the device was still recording from the top of the hotel room’s armoire.

Riccio claims he forgot the recorder was in the room, leaving it to capture more than 10 hours of audio before he returned to the room and retrieved it.

The enterprising Corona, Calif.-based collectibles dealer then sold the audio for more than $100,000 to the gossip Web site, TMZ.

Caldwell said he was “frustrated” after a colleague saw it online and told him it.

The detective contacted Riccio five days after the run-in occurred, on Sept. 17, and asked Riccio to send him a copy of the audio he captured. Caldwell received the FedEx the next day, five days after the alleged crimes took place.

Riccio also couriered seven audio files to the police. Caldwell said he also drove out to Riccio’s home later that week, on Sept. 21, 2007, to retrieve the device Riccio says he used to record the audio.

The authenticity of the recordings and the recorder itself, along with the transcripts Caldwell produced, have been highly disputed by the defense.

The jury has already heard from two FBI experts, a forensic examiner and electric engineer, Jason Abramowitz, and an audio analyst, Kenneth Marr.

Earlier in the day, Marr told the court through his video deposition that he could not say whether or not the audio files from Riccio’s recorder had been manipulated or altered.

He also said it wasn’t possible to tell the difference between the files he was given and the files he downloaded, digitally manipulated and uploaded again: The files appeared to be the same.

More than a dozen audio recordings containing about 14 hours of audio are expected to be submitted as evidence.

Caldwell told the prosecutor, Chief District Attorney Christopher Owens, that he thought the recordings should be used as evidence.

“There’s no problem if there’s blanks in inaudible portions. It doesn’t make the rest of it that’s audible inadmissible,” Caldwell said. “The most substantial portion of it all is really fairly audible and accurately covered in the transcript.”

The detective said he has spent hundreds of hours listening to the contested audio recordings, which Riccio secretly took on Simpson’s hotel room, around the hotel pool, at Palace Station, and while talking with Simpson over the phone.

After reviewing a file recorded around the pool at the Palms, Caldwell said, “We realized that a significant amount of the planning … occurred at the pool area at the Palms.”

Caldwell’s transcript of the poolside conversation attributes some of the dialogue to Stewart. Stewart, meanwhile, says he wasn’t at the poolside meeting, and the voice on the tape isn’t his.

This is of particular interest to the North Las Vegas mortgage agent’s lawyer because three of the charges Stewart faces – conspiracy to commit kidnapping, conspiracy to commit robbery, and conspiracy to commit a crime – carry minimum one-year sentences.

Stewart’s lawyer, E. Brent Bryson, has spent much of the day challenging the admissibility of the recordings and the transcripts Caldwell created.

While Simpson’s attorneys said they challenge “six or seven” words in the transcript, they, too, object to Caldwell’s determination of who said what.

District Judge Jackie Glass decided, however, to allow the jury to use the audio transcripts as guides while they listen to the recordings in court, but the judge chose not to provide them with transcripts to use in the jury room.

“The tapes will be back there (in the jury room) and they can play them over, and over and over again,” Glass said.

“(The) tapes should be what ultimately guide them,” Glass said, adding “they will have to take good notes.”

Caldwell said that because so many people are on the tape – there were 10 men in the room when the confrontation was going on – it is difficult to decipher much of the dialogue.

“Because there’s so many conversation going on … even after having listened to them for hours on end, I can listen to it right now and I’ll pick up bits and pieces of things that aren’t in the transcripts.”

In addition to Riccio’s recordings, investigators also obtained a micro-cassette tape containing additional recordings taken that day.

Lawyers for one of the men who accompanied Simpson and the others that day, Michael McClinton, contacted police to tell investigators about the tape.

McClinton surrendered to police and has since cut a plea bargain in exchange for testimony. His lawyer says his client will tell the court that Simpson asked him to bring the two guns that were allegedly used in the altercation.

Stewart’s lawyers have said their client had no knowledge guns were going to be involved.

Simpson, meanwhile, has maintained that no guns were used in the raid, and that he and his colleagues only took items from Fromong and Beardsley that belonged to him.

Fromong on Tuesday said “They took everything except two baseball bats.”

Caldwell testified today, however, he and fellow officers noted several memorabilia items in the room after the alleged robbery, including Mohammad Ali’s boxing gloves and checks signed by Marilyn Monroe.

He will complete his testimony Thursday, when the trial will resume at 8 a.m.