Monthly Archives: October 2012

Tricks for Obtaining DNA

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DNA

 

In the Law & Order: LA episode, “Ballona Creek,” Detective Tomas Jaruszalski picks up a suspect’s discarded cigarette butt for DNA analysis. This type of surreptitious DNA collection is so common in fiction, that the practice doesn’t even merit a raised eyebrow. In real life, surreptitious DNA collection sparks protests from members of the public. At the same time, law enforcement agencies argue that the practice is justified, because an individual has no privacy interest in an abandoned DNA sample.

Instead of retrieving an abandoned item for DNA, law enforcement officials sometimes trick a suspect into giving up a DNA sample. In a case reported in 2009, police sent a letter about a class action lawsuit to a suspect. Eager to join the case, the suspect signed a form and mailed it in a self-addressed envelope. Investigators extracted DNA from the saliva on the envelope flap and found a match to a semen sample gathered from a 1982 rape-killing.

More recently, ABC News reported a recent success for a case concerning the 1976 killing a 70-year-old woman. During a recent review of the cold case, investigators obtained DNA from the old evidence.

The police had a suspect, now they needed the suspect’s DNA to check against the evidence DNA. So, they used a phony “gum chewing survey” and got their saliva sample from the suspect. The results led to an arrest.

An Expert’s View on DNA Evidence

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Finding DNA

 

NPR recently posted an interesting story entitled “Analysing The Evidence On DNA.” Ira Flatow interviewed Greg Hampikian, Director of the Idaho Innocence Project, about the uses and abuses of DNA evidence. The topics that they discussed include:

  • problems with DNA evidence collection,
  • advantages and disadvantages of the high sensitivity of modern DNA analysis,
  • use of DNA evidence in investigations, and
  • myths about evidence analysis perpetuated by TV shows.

The interview is definitely worth a look (or a listen).

Forensic Science for Writers (A little BSP)

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Forensic Science for Writers book cover

I have two news items about my book, Forensic Science for Writers.

First, the good folks at The Writers Store decided to offer my book. As most writers know, The Writers Store is not only a brick and mortar store, but also a huge online shop devoted to helping writers.

Second, Moira Allen, editor of Writing-World.com and author of books, such as Starting Your Career as a Freelance Writer, kindly offered her view of Forensic Science for Writers:

 If you’ve been getting your forensic details from television, try this instead! It’s packed with an amazing amount of detail, and helps the reader sort out not only what can be done, but exactly who does it. Over and over, I found myself exclaiming, “I didn’t know THAT!” Now I do!

Maggots Identify Victim

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Fly and DNA

 

Experts in the field of forensic entomology can estimate time of death by examining insects that inhabit a corpse. If a corpse is older than 72 hours, then the time of death can be estimated by identifying the species of maggots infesting the body. Maggots can provide more information than this, according to a September 28 report by Sara Reardon in New Scientist.

The case began when Mexican police discovered a body that had been burned beyond recognition. The body was so damaged that investigators could not recover DNA for identification. They did, however, recover human DNA from the digestive tracts of maggots that had been consuming the body.

A team of pathologists at the Autonomous University of Nuevo León in San Nicolás, Mexico analyzed the DNA and determined that the victim had been female. The police suspected that the body belonged to a woman who had been abducted 10 weeks earlier. The pathologists performed a paternity test using the recovered DNA and DNA from the abducted woman’s father. The results revealed a 99.7% chance that they had found the man’s abducted daughter. This case marks the first time that investigators successfully used human DNA extracted from the guts of maggots to identify a victim.