The way people think about the collection of DNA evidence is guided by present-day, fast-paced television shows where the DNA can make or break a case. In those shows, crime scene experts rush to crime scenes and study the art of blood splash patterns and have an amazing knowledge of how to find the most microscopic trace evidence, like from something out of the shows Dexter or CSI.
The problem with the Central Park 5 case is that it happened in 1989. It was a time when DNA evidence was only one year old in New York City. The police hardly knew about it and there was hardly the kind of experts walking around like Dexter who had vast amounts of knowledge on how to preserve and gather evidence from a crime scene. In fact, in the Central Park 5 case, the crime scene isn’t where they gathered DNA evidence from Patricia Meili. No. Instead, they waited for the medical people to stabilize a woman who was nearing death. They put her life first and carried her to the hospital.
Once they saw a window of opportunity they did a swab of her cervix and rectum and allowed the medical professionals to continue saving her life. That, her pants, and a sock that was found lying by her on the scene are the only three places where DNA was found.
This is important because none of the Central Park 5 claimed to have penetrated her. And, since the only places where they found decent samples were the sock and her cervix, this leaves room for there to have been multiple attackers. The DNA on her pants turned out to be her boyfriends.