development in the technology for them to do the kind of analysis to connect to a suspect. reporter: in 2020, the fbi launched that next level dna testing with new protocols for forensic crime labs. this was one of the first cases pursued using this technology. the shaft of the hair has mitochondrial dna. over time and decomposition, the root disappears, and all you have left is the shaft. mitochondrial dna is much smaller, and it is much more robust, so it lasts a much longer time. it endures in hair samples, even if you don t get a root. all you need is about one centimeter of hair to get a genetic profile. reporter: and those microscopic bits of hair would eventually lead to a breakthrough. hairs were identified on one of the remains that were not from the victim. the problem is, they did not
reporter: in 2020 the fbi launched that next-level dna testing with new protocols for forensic crime labs. so this was one of the first cases that were pursued using this technology. the shaft of the hair has mitochondrial dna. over time and decomposition the root disappears and all you have left is the shaft. mitochondrial dna is much smaller, and it s much more robust. so it lasts a much longer time. it s present in hair samples. even if you don t get a root. all you need is about one centimeter length of that hair to get a genetic profile. reporter: and those microscopic bits of hair would eventually lead to a breakthrough. there were hairs identified on one of the remains that were not from the victim. the problem is they didn t have anyone to compare it to. reporter: enter suffolk county police detectives working undercover to surveil heuermann. so they began collecting evidence from his home. the surveillance team picked up 11 bottles and brought that
launched that next-level dna testing with new protocols for forensic crime labs. so this was one of the first cases that were pursued using this technology. the shaft of the hair has mitochondrial dna. over time and decomposition the root disappears and all you have left is the shaft. mitochondrial dna is much smaller, and it s much more robust. so it lasts a much longer time. it s present in hair samples. even if you don t get a root. all you need is about one centimeter length of that hair to get a genetic profile. reporter: and those microscopic bits of hair would eventually lead to a breakthrough. there were hairs identified on one of the remains that were not from the victim. the problem is they didn t have anyone to compare it to. reporter: enter suffolk county police detectives working undercover to surveil heuermann. so they began collecting evidence from his home.
whenever the target phones would bounce off a cell tower, if the heuermann personal phone bounced off a tower, it was always consistent and in close proximity with the target phones. reporter: prosecutors say heuermann was keeping tabs on them, using those phones to make more than 200 searches about the investigation. detectives say another clue came from pizza crust taken from the garbage, matching dna profiles from hair samples taken from the victims. today, this youtube video from more than a year ago resurfacing, of heuermann discussing his firm. okay. rex i m an architect. i m an architectural consultant. i m the troubleshooter. born and raised on long island. reporter: tonight, neighbors filling the streets around his house, shocked to learn the
sounds admitted jealousy, kathy doting on albert, a rejected proposal. all of it seem to add up to motive. but motives don t prove murder. there was still no physical evidence tying sam to the crime. all of the blood on the car had been dusted and it was all cafés. then, welcoming the case file, detective darren why it learns something shocking. there were blood and hair samples that had never been sent to the crime lab. and when those samples were analyzed, they pointed to a whole new suspect. coming up new dna. and a new man in the hot seat. he sat there and put his best in front of his mouth to keep himself from talking. when dateline continues.