20160621 - crime solving

How Science Is Putting a New Face on Crime Solving

Advances in forensics are giving us an unprecedented ability to solve cases—and exposing mistakes in some investigations.

On the morning of November 23, 2009, a cyclist riding near Lake Charles, Louisiana, discovered the body of a young woman lying near a country road. Her face had been beaten beyond recognition, but an unusual tattoo led the police to identify her as 19-year-old Sierra Bouzigard. Investigators from the Calcasieu Parish Sheriff’s Office, headed by Sheriff Tony Mancuso, immediately set about reconstructing her final hours. The people who last saw Bouzigard alive had let her use their phone. The number she dialed gave police a lead. 

Bouzigard’s assailant had also left behind a promising clue. From tissue caught under her fingernails as she struggled for her life, the detectives were able to pick up a clear DNA sample. To find the killer, all they needed was a match. The number she had dialed led police to a crew of undocumented Mexican workers. “So we started getting warrants for DNA swabs, getting translators, working with immigration,” Mancuso recalls

But none of the Mexicans’ DNA matched the sample from the crime scene. Nor was there a hit in the FBI’s database of prior felons, missing persons, and arrestees, a system known as CODIS—the Combined DNA Index System. The investigators continued to issue calls for people with any information to come forward, and Bouzigard’s family offered a $10,000 reward. But the case grew cold.

Then, in June 2015, Monica Quaal, a lead DNA analyst at the lab that works with the sheriff’s office, learned about an intriguing new way of exploiting the information contained in a DNA sample—one that would not require a suspect’s DNA or a match in a database. Called DNA phenotyping, the technique conjures up a physical likeness of the person who left the sample behind, including traits such as geographic ancestry, eye and natural hair color, and even a possible shape for facial features. Quaal immediately thought of the Bouzigard case, in which the DNA left at the scene was virtually the only lead. She contacted Mancuso and Lt. Les Blanchard, a detective on the case, and they sent their sample to Ellen Greytak, director of bioinformatics at Parabon NanoLabs, a company specializing in DNA phenotyping.


http://www.nationalgeographic.com/magazine/2016/07/forensic-science-justice-crime-evidence/