michael farrar both had similar antibodies in their systems. antibodies designed and structured to recognize and seek out the target invader, ricin. dr. richardson discovered something else. the number of ricin antibodies in farrar's system was staggering. >> in the case of dr. michael farrar, it's not that perhaps he was exposed three times. a certain immune response would have been produced the first time, a response that would have lasted a few weeks. on second and third and perhaps other exposures, a separate immune response would have been produced. for each one of those exposures and the latter exposures would have produced a response in antibodies that would be present in the blood for, again, many months to perhaps a few years. >> debora green was charged with two counts of murder and two