Lawyers from both sides pored over surveillance video Tuesday in the case of a former U.S. Marine imprisoned in Mexico to work out which tapes were relevant to his arrest and should be shown at his hearing.

But the Marine, Sgt. Andrew Tahmooressi, was not present at the hearing, which adjourned Tuesday afternoon so the attorneys could select the relevant videos to be shown when court resumed several hours later.

"I am certain that the videos will support my client's version of the facts," his lawyer, Fernando Benitez, said as he left the Tijuana courthouse during the break. "I'm not sure that they will support even partially what the Custons agents claim happened."

The surveillance tape was shot by Mexican officials on the night of Tahmooressi's arrest.

Benitez also was expected to introduce a psychiatrist who could show how Tahmooressi's mental condition has deteriorated during nearly six months in prison.

Tahmooressi has been held since March 31, when he says he mistakenly crossed into Mexico with three legally-purchased and registered guns in his truck.

Benitez earlier told Fox News he was most curious about the fact that Mexican Customs officials dragged their feet in turning over the video, to the point that Judge Victor Octavio Luna Escobedo had to order them to comply.

“He set forth an order whereby basically he told Customs, ‘I’m not asking. I’m telling you to deliver the tapes,’” Benitez told Fox.

Benitez said it is likely the judge will fast-forward through irrelevant portions of the video, none of which has audio. But he said it could prove illuminating.

“Tomorrow, we’ll see who’s been truthful and who has not,” Benitez tweeted Monday.

The attorney, who once successfully represented former Tijuana mayor and current owner of the Xolos soccer team Jorge Hank Rhon on weapons charges, is working the case on several other fronts. He plans to file a motion to suppress evidence gathered against Tahmooressi on the basis that his detention was illegal from the beginning.

Benitez will also eventually present a report from a psychiatric expert who will focus on Tahmooressi’s Post-Traumatic Stress Disorder, a result of two combat tours in Afghanistan. Benitez believes that Tahmooressi cannot receive PTSD treatment in Mexico and an eventual prison sentence would be inconsistent with the country’s policy of providing rehabilitation to prisoners.

Tahmooressi’s team is also working on a video which will show how easy it was to accidentally cross into Mexico on the night of March 31, when the signage was not clear. It’s since been replaced, making future incidents like Tahmooressi’s less likely.

If Tahmooressi is convicted, he faces six to 21 years in prison. Tahmooressi served four years in the Marines before being honorably discharged in November 2012. Tahmooressi's mother, Jill, was also present for her son’s hearing today.  

Dan Gallo is a Fox News Channel Field Producer based in Los Angeles. Follow him on Twitter: @DanGallo