What is a Silent Witness and how do you become one?

On Aug. 4, 1997, Fiona Yu, 21, was found sexually assaulted and strangled by an attacker at her apartment in Tempe.

Yu, who was an Arizona State University senior studying accounting, was last seen by her neighbor about 4:30 p.m., when she was riding a bicycle around her residence, police said.

About 90 minutes after, her roommate found Yu barely alive on the second floor. She later died of her injuries.

Tempe police detectives tracked down a few possible suspects but soon realized their DNA testing did not match a DNA sample collected at Yu’s apartment.

A new DNA technology being used by Tempe police is bringing renewed hope to solving the 20-year-old murder case. 

What is Snapshot DNA testing?

The department, for the first time in an investigation, used predicted image technology called Snapshot DNA Phenotyping from a Virginia-based DNA lab, Parabon NanoLabs. 

The technology has been used by police in Phoenix, Mesa and other Arizona cities to generate suspect composites based on DNA.

The technology uses a DNA sample collected from a crime scene to create a composite image that predicts what a suspect is likely to look like.

A Tempe Police Department news release included images generated by the technology of a man with brown eyes and black hair.

“We are hoping that getting this composite would draw out people’s memory,” Tempe police Det. Lilly Duran said.

Duran said Tempe police never stopped trying to identify the suspect, and though the predicted image might not exactly match the suspect’s face, she still hopes this will draw renewed attention to the 20-year-old investigation.

Nanolabs, law enforcement

Snapshot DNA Phenotyping became available for law-enforcement agencies in late 2014, said Ellen McRae Greytak, director of Bioinformatics at Parabon NanoLabs.

NanoLabs provided a phenotype DNA analysis to more than 100 law-enforcement agencies in the United States and Canada, and 13 of them led to an arrest of a suspect, Greytak said.

The technology was most recently used in an arrest made on July 25 in New Mexico, when the Albuquerque Police Department arrested a suspect in a 2008 brutal assault case

Unlike traditional DNA testing, Snapshot makes it possible to predict a person’s face with at least 1 nano gram of DNA, which can easily be acquired in most crime scenes, Greytak said. 

Nanolabs conducted many blind tests to see how closely Snapshot generated an image of an unknown person. The results were similar to the person’s appearance, Greytak said.

The current version of Snapshot doesn’t predict age, height or weight, but Greytak said she hopes the technology will progress enough to do so in the future.

Snapshot costs $3,600 per phenotype analysis, Greytak said, so crime investigators could narrow down a list of suspects up front.

“The purpose of it (Snapshot) is to prioritize possible people that you are looking at and exclude people, especially,” Greytak said. 

In Phoenix, investigators used Snapshot in the case of a mother who discarded her newborn baby at Sky Harbor International Airport in 2005.

Mesa is using the technology to track down a man who sexually assaulted a 4-year-old child in January, according to police.

The departments said no arrests have been made in those cases.


A scream from a college student, a small Arizona community unable to help, and a 30-year-old unsolved murder

Phoenix police use DNA composite to try to help solve 2005 cold case

Mesa police use DNA technology to create composite sketch of man wanted in sex assault

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