This is a common mistake in police procedural series, but DNA results are literally never "same day". In fact, the entire process takes about five working days - say 40 to 50 hours of actual lab time - and because DNA laboratories around the world have a huge backlog of cases, most results won't come back in less than three months. In the case of a child abduction, the police could request a rush, but they'd need to wait three to five days before any usable results came back. For the results to be admissible in court, the lab techs would need to submit a written report.