U.S. Marine locked in a Mexican jail for more than three months finally had his day in court facing the charge he brought guns into Mexico illegally and ABC's Reena ninan has the story. Reporter: This... See More
U.S. Marine locked in a Mexican jail for more than three months finally had his day in court facing the charge he brought guns into Mexico illegally and ABC's Reena ninan has the story. Reporter: This morning U.S. Marine reservist Andrew tahmooressi is back in a Mexican jail ordered overtight to remain in custody on gun charges near Tijuana where he's been locked up 102 days. It's been a grueling nine hours. Reporter: The evidentiary hearing lasted more than eight hours and was tahmooressi's first chance to plead his case in court. The California native seen arriving at the xhous under heavy guard was arrested March 31st after he says he got lost and crossed the Mexican border with three firearms in his pickup truck. I crossed the border by accident and I have three guns in my truck and they're trying to process -- they're trying to take my guns from me. So you're in Mexico. Yeah. There is nothing I can help you with. Reporter: Tahmooressi's mother says she was able to spend 20 minutes with her son after the hearing. He's very strong. He's very strong and positive and he's confident. Reporter: The state department is actively engaged in the case. Officers have visited him 13 times and 71 members of congress have signed a bipartisan letter asking the judge for leniency. His newly hired attorney is hopeful. We feel it was a success and we feel we are finally on the right track. Reporter: Still, there are doubts unlike American law in Mexico what is guilty until proven innocent and the decision rests solely in the judge's hands. For "Good morning America," Reena ninan, ABC news, New York.
This transcript has been automatically generated and may not be 100% accurate.