Tag Archives: forensic

Who Are You? (Who, who, who, who)

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Finding DNA

 

Technicians painstakingly extract DNA from a few cells recovered from a crime scene. They duplicate segments of the DNA using the polymerase chain reaction. After analyzing the selected DNA fragments, they upload the results into the FBI’s national DNA database, the Combined DNA Index System (CODIS) Program. The result: No hits. The DNA profile is not in the database. Now what?

Researchers at Israel’s Tel-Hai Academic College may provide an answer with a DNA composite portrait based on connections between genes and external human traits.

“The new development will provide tons of leads,” research team leader Dani Bercovich told news website NoCamels.com. “We’ll know the sex of the offender and be able to estimate his height, age range, color and type of hair, eye color and ethnic background — even whether he is right or left-handed.”

Regardless of whether this technology is realized, it certainly can find a place in a mystery or crime story.

A Real Forensic Scientist

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How to contaminate evidence

How to contaminate evidence: No coveralls, no gloves, no booties, and no sense.

 

The website of the Toronto Star has interesting profile of Christine McCarthy, a forensic scientist at Toronto’s Centre for Forensic Sciences. In the July 13, 2012, posting entitled “Hair: Forensic scientists can tell a lot about a person from one strand of hair,” reporter Tony Wong describes McCarthy at work.

In the field, she dons a disposable lab coat, mask, gloves, and a hairnet before she starts her search for trace evidence. This is a very different approach than that used by crime scene technicians on television. Wong compared McCarthy to CSI’s Catherine Willows. “Except I wouldn’t have a Hummer or wear high heels on the job,” McCarthy told him.

She mentioned another of the many differences between CSI characters and her colleagues at the Centre for Forensic Sciences. “They seem to solve everything in an hour,” McCarthy said, “and I can tell you it takes a lot longer than that.”

McCarthy specializes in the analysis of trace evidence, especially hair. Wong’s article offers an overview about this aspect of forensic science.

GSR Speaks Again

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Traditionally, gunshot residue contained gunpowder residues (such as partially-burned or unburned gunpowder) and lead residues. However, an increasing number of ammunition manufacturers produce ammunition that contains little or no lead. This change is good for the environment, but creates a challenge for criminal investigators, because crime labs test for gunshot residue by detecting the presence of lead, barium, and antimony.

During June 2012, forensic researchers at Florida International University announced a new technique that can potentially link a suspect to fired ammunition by identifying the chemical signature of the powder inside a bullet. In this approach, a chemist analyzes the chemical composition of a bullet’s smokeless powder. The method reveals the particular formula of the smokeless powder, which further identifies the manufacturer of the powder.

“Crime labs all over the country are faced with the reality that their only way to analyze whether a gun was fired by a suspect may become obsolete,” said chemistry Professor Bruce McCord in a press release. “Our discovery is not only more accurate, but it can determine the type of gunpowder used in a crime even if the gun is never recovered.”