(Tijuana) -- The trial is underway for a U.S. Marine jailed in Mexico on weapons charges. Sergeant Andrew Tahmooressi was arrested March 31st after he crossed the border with guns and hundreds of rounds of ammunition in his pickup truck. Tahmooressi's lawyers claim the Marine's rights were violated because he wasn't provided a translator to explain why he was arrested on March 31st. Tahmooressi did two tours of duty in Afghanistan. He says he crossed the border near at San Ysidro by mistake.