kelsall made a discovery that would change the course of the investigation. he found that crawford had a heart pacemaker implanted in his chest. >> a pacemaker is a way of stimulating the heart. it delivers anything from about two to five volts into the heart to make it pace, that is, contract. >> i was vaguely aware that pacemakers have a recording unit inside them. >> if so, crawford's pacemaker might reveal the exact time of his murder. unfortunately, pacemakers hold information for only a short time before it's recorded over. the autopsy took place almost 30 hours after the murder, which meant the pacemaker memory might have already been erased. >> we knew that we didn't have a great deal of time, that we were running out of time. >> the hospital's pacemaker specialist quickly scanned it to gather the pacemaker data and load it onto a computer. in an unbelievable turn of events, this particular pacemaker had something very few pacemakers had at the time. a computer chip that had what's called an event memory. >> this is unique to this product and, is in f