. >> two of these potential witnesses were sent to police sketch artist, gil samora. >> i asked them if they saw him again would they recognize him. they say yes, then i know that i can draw the sketch. >> with each witness, zamora tried to induce a state of deep relaxation and then had them describe what they saw. eventually, these two drawings emerged from witnesses who had never spoken with each other. except for the sunglasses, the sketches were virtually identical. >> they were two independent witnesses, and they did not know each other. i think these witnesses both saw the same person. >> then police got a huge break. investigators using k-9 teams identified a potential lead. >> they were able to track a scent trail to a residential area in concord that was very close to the canal trail. >> a background check revealed a man living in this neighborhood had a criminal history. he also looked similar to the composite drawings. his name was mark fisher. >> he was known to be violent, violent to his relatives, violent to police officers and to other public officials. >> witnesses in