so the new cold case unit began their investigates with the oak leaves found 20 years earlier in the trunk of larry bruce's car. >> it was our theory when he opened the trunk to take the body out, some of the oak leaves fell into the trunk of his cadillac. >> and information presented in this very television series suggested a new way to test them. >> i was watching one night and they had a story about out west in arizona had done a plant dna case. >> the crux of that investigation was a seed pod found in a suspect's truck which was later matched with plant dna to the palo verde tree next to the victim's body. ryan bolt contacted the scientist who pioneered plant dna analysis and asked them to test the oak leaf found in larry's trunk to determine if it came from the oak tree near judy's body. unfortunately, too many years had passed and scientists were unable to extract any dna to the leaf. but to their credit, police didn't give up.