NYPD: 2 types of DNA tie suspect to Vetrano murder

Chanel Lewis, 20, of East New York, Brooklyn, is charged with the murder of Karina Vetrano, who was raped and strangled while running in a park in Queens. Police sources said he was on their suspect short list, but the DNA match put him in handcuffs.

NYPD Chief of Detectives Robert Boyce said Lewis voluntarily gave the police a DNA sample. Chief Boyce also says they have two types of DNA evidence linking Lewis to the brutal murder. I went to the Office of the New York City Chief Medical Examiner to find out what that means.

Timothy Kupferschmid is the chief of laboratories for the OCME. He said that there is autosomal DNA and mitochondrial DNA. The state-of-the art laboratory can analyze DNA from as small a sample as a few cells, even if someone brushed up against a person. They follow extremely strict guidelines, which are expected to come under scrutiny in the Vetrano case.

The Legal Aid Society, which is defending Lewis, said: "We have a full defense team working on this case, including our DNA unit dedicated to scrutinizing the evidence collected by local authorities."

Kupferschmid said it is important to keep in mind that the science itself is impartial and that it is up to police and prosecutors what they do with it.