Three years ago, George Russell Weller told Santa Monica police officers he had no idea how his Buick LeSabre accelerated through a crowded farmers' market, killing 10 people and injuring 60 more. He also said he had no idea why the car stopped. Was the cause an extended "senior moment" or a felony crime? The CHP says the most likely explanation is "pedal error," a driver mistakenly hitting the accelerator instead of the brake. It's all too common among elderly drivers, and Weller was 85 at the time. Today he went on trial, charged with 10 counts of manslaughter by the Los Angeles District Attorney with a maximum possible prison term of 18 years.