Of the 85 Americans in the La Mesa prison in Tijuana, Mexico, six are senior citizens who bought medications in Mexico without a prescription. The Rev. David Walden, who ministers to Americans at the prison, said the seniors were only trying to save money buying their medications south of the border where prescription drugs are much cheaper."They are accused of trafficking drugs and end up in La Mesa. So we have senior citizens and it breaks my heart," Walden said.Former inmate Freddy Roberts was arrested outside a pharmacy in Mexico after buying medication for his high blood pressure. Police officers asked for a prescription, but he didn't have one."I didn't go over with intention of committing a crime. People have to be careful going down there. They will pick you up," Roberts said.Roberts was sentenced to four years in prison.Dr. Leon Dychter said not only do you need a prescription, it must to come from a Mexican medical doctor or dentist."The first thing is to respect the laws here and you're not going to be in any problems at all," Dychter said.Walden warns, if you don't play by the rules in Mexico, don't expect American justice."In Mexico, they don't have due process, so you're guilty until you prove yourself innocent," Walden said.And that can take years inside La Mesa prison and thousands of dollars.For more information, visit the AARP Web site.