then investigators asked their third suspect, william deparvine, for a dna sample. said no. >> we don't have any probable cause at this point in time in the investigation to indicate that mr. deparvine is involved in the murder. therefore, we don't have enough information to draw a search warrant. >> without a warrant, police couldn't get a genetic sample directly from deparvine. but there were other ways. >> we were looking for him to either eat something, drink something and discard it, chew gum and discard it, or even spit so that we could swab that up. >> a team of detectives was assigned to follow deparvine everywhere he went, hoping to somehow get his dna sample. deparvine had earned a law degree while he was in prison, and he was very careful, either because he was disciplined or he knew he was being followed. >> he led a very monotonous, very bland type of life. would get up in the morning. he would go to work. he would come back home and stay inside his little apartment and go to sleep. >> deparvine was a construction worker, and he had no social life to spe