LAS VEGAS -- Witness testimony continued Wednesday in the O.J. Simpson armed robbery trial.

The focus for the majority of the day was on the audiotapes made during the alleged heist.

Thomas Riccio was waiting in the wings to testify. He is the one who recorded more than 10 hours of audio before, during and after the alleged robbery.

Prosecutors are trying to lay the foundation for the authenticity of those tapes before they bring Riccio on the stand.

Day three of witness testimony in the Simpson trial started with a taped appearance of Kenneth Marr, an FBI audio analyst. His job was to authenticate digital and analog tapes that were made during the alleged heist.

“The analog tape that I looked at was uninterrupted,” Marr said.

But Marr couldn't say the same for the digital recordings. He could not say whether or not the recordings were manipulated.

Metro police Detective Andy Caldwell was next to testify. Caldwell was called to the Palace Station Hotel and Casino last September when 61-year-old Simpson and five other men allegedly robbed two sports memorabilia dealers.

“First thing I asked security was if Mr. Simpson was on property,” Caldwell said.

Caldwell interviewed Riccio, the middleman who set up the meeting between Simpson and the two alleged victims. Caldwell said the discussion with Riccio was frustrating.

“I wanted him to tell me what occurred that night, but he didn't want to tell me what happened until he told me what happened before that night. Then he finally told me what happened,” Caldwell said.

But Riccio never told detectives he made audio recordings of the incident.

“The recording device was placed there, and he never told us about it,” Caldwell said.

Instead, investigators found out about the recordings several days later when they saw them on www.tmz.com.

Defense attorneys have said Riccio sold those tapes for more than $100,000.

Defense attorneys also pointed out that Riccio didn't agree to turn over the tapes to investigators until he was guaranteed immunity from prosecution.

Simpson and his co-defendant, Clarence Stewart, are facing 12 charges, including armed robbery and kidnapping.

Four other men involved copped plea deals and are expected to testify against Simpson.

For more information on the Simpson case, visit the case's special section or view the national coverage.