Man arrested in deadly 2011 stabbing of teenager in Phoenix

Police have made an arrest in a deadly stabbing in Phoenix that left a 19-year-old teenager dead nearly 10 years ago.

Thirty-two-year-old Freddy Martinez is facing several charges, including first-degree murder, second-degree murder and kidnapping.

According to court documents, the stabbing happened on May 28, 2011 when three teens were walking in an area near 83rd Avenue and Lower Buckeye Road.

A group of men reportedly pulled up in a white car, running out and chasing down the teenager. 19-year-old John Williams-Ryan, who was visiting from another state, was not able to escape and was beaten and stabbed to death.

A DNA search last year led police to Martinez.

"The victim may have scratched the suspect and managed to get the scrapings, and they can get plenty of skin samples from the suspect," said Sree Kanthaswamy, a professor in genetics and forensic science at Arizona State University.

The teen victim's nail clippings had been kept for years. On January 2020, investigators had found a match in Arizona's DNA index system, leading them to Freddy Martinez.

He was detained on May 3 and initially denied knowledge of the stabbing. Once police revealed his DNA had been found under the victim's fingernails, police say he admitted involvement in the attack.

Martinez's bond has been set to $500,000, and his next hearing is May 11.

How DNA plays a role in solving cold cases

"The victim may have scratched the suspect and managed to get the scrapings, and they can get plenty of skin samples from the suspect," said Sree Kanthaswamy, a professor in genetics and forensic science at Arizona State University.

It had taken years for police to find a DNA match for the stabbing in Phoenix.

"It brings a lot of closure to the victim and the victim's family and also people involved in these cases," professor Kanthaswamy said.

The ASU professor says that DNA research continues to improve quickly. The university's forensic science program is one of its fastest-growing programs and serves as a pipeline for students who want to work in crime labs.

"We train our students precisely in these types of cases," the professor said. "How do you help solve a cold case? How do you get DNA? How do you analyze the DNA? How do you quantify the DNA?"

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