Monthly Archives: July 2012

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.

Avoid the Parallel Worlds of TV Forensics

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A compromised crime scene.

Where’s the medical examiner’s agent? Who contaminated the body by draping it with the blanket? Has anyone collected trace evidence yet?

 

Anyone who watches CSI and other forensics-based series might imagine that forensic scientists live glamorous lives. They work in labs illuminated by mood lighting, where they need an hour or less to generate exciting data using complex analyses. Who needs specialists? A TV forensic scientist can perform any type of test. In between quickie lab tests with equipment sure to burst any local government budget, forensic experts speed to crime scenes in their Hummers. They arrest suspects, interrogate them, and saunter back to their labs. All of this is a reflection of reality – an alternate reality, that is.

Beware of misconceptions created and perpetuated by TV shows and films. Lee Lofland, a veteran police investigator, writer and consultant, serves up “10 Forensic Myths Spread by TV,” which is posted on his website. It’s a good place to start separating fact and fiction.

Microstamping Could Yield Macro Benefits

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Example of microstamp placement

 

Traditional firearm identification is based upon the fact that every weapon has unique features introduced during manufacture and later caused by wear. These characteristics of a firearm create striated and impressed marks on fired ammunition that enable an examiner to identify a round of fired ammunition as coming from a particular gun. This analysis requires an examiner to have access to a suspect firearm that can be test fired to produce a bullet and cartridge case.

A method called microstamping could radically change firearm identification practice. Using lasers, unique alpha-numeric codes are added to certain parts of a firearm, such as the firing pin and breech face, and these identifiers are stamped onto a cartridge when fired. A code could reveal a firearm’s manufacturer, model, and serial number. The serial number alone would lead investigators to the identity of the person who first purchased the firearm.

Proponents of microstamping claim that the technique would not only aid a criminal investigation, but also would reduce the supply of illegal firearms. Microstamping, the argument goes, would deter people with clean records (straw buyers) from purchasing guns for criminals.

Since the technique was proposed, microstamping has generated controversy about the method’s reliability. A study posted on the New Yorkers Against Gun Violence website indicates that microstamping works.

Book’em Danno . . . and Get DNA

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DNA from Arrestees

 

The FBI’s national DNA database, the Combined DNA Index System (CODIS) Program, stores DNA profiles. Leads from DNA evidence can be generated from CODIS’ Convicted Offender Index and the Forensic Index. CODIS also contains an Arrestee Index of DNA profiles of people arrested in states where local law allows the collection of samples.

Despite continuing debates about collecting DNA from arrestees, the U.S. federal government and 28 states have laws that authorize arrestee DNA collection. In their June 2012 NIJ Journal article, “Collecting DNA from Arrestees: Implementation Lessons,” Julie Samuels, Elizabeth Davies, Dwight Pope, and Ashleigh Holand explore the history and scope of this controversial practice. A copy of the article is available from the National Institute of Justice website.

By the way, the FBI imposes a requirement that states must meet before arrestee DNA profiles can be uploaded into CODIS: The FBI must approve the state’s system for expunging a DNA profile if a charge is dismissed or results in acquittal. In most states, the arrestee bears the burden for starting an expungement procedure.