RSS

DNA and Hair Color

03 Apr

DNA is one of the most important criminal investigative tools ever discovered. It identifies an individual with virtually 100% certainty. If someone leaves blood, semen, saliva, or some other bodily fluid at a crime scene and if it is found good condition, DNA extracted from the sample can accurately tie that person to the scene. Doesn’t mean he’s guilty just that he left DNA there. Something he’ll need to explain.

But what if there is no suspect? What if the person who left the sample is completely unknown as often happens, particularly with serial predators. These “stranger murders” are often the most difficult ones to solve because there is no apparent “connection” between the murderer and the victim.

This means that any descriptive evidence that can be obtained regarding potential suspects is of paramount importance. If someone witnessed a particular person running in the distance or a particular type of car cruising the neighborhood or a particular type of clothing is left behind, then these can be added to the offender profile and help narrow the search. This is one of the important elements of the Violent Criminal Apprehension Program (VICAP). Through this program violent crimes committed by unknown perpetrators are uploaded into databases. If multiple crimes perpetrated in various parts of the country have similar characteristics then the linkage of these crimes can often build a more firm description of any possible perpetrators.

For example, what if a murder in Florida had certain characteristics (method of murder, weapon used, method of body disposal, etc.) and similar characteristics were found in a murder in New Jersey? What if in Florida someone had seen the perpetrator from a distance and judged him to be a tall thin male while in New Jersey someone saw a black van leaving the scene? If these two crimes were never linked then police in both areas would not know that they were looking for a tall thin male who drove a black van. And so on. The more evidence that can be accumulated regarding serial crimes the better a description of possible perpetrators can be constructed.

Now it seems that hair color can be obtained from DNA. So a perpetrator who leaves behind a drop of blood might also leave behind evidence of his hair color. It seems that red hair and black hair can be determined with an accuracy of approximately 90% while brown and blond hair can be determined approximately 80% of the time. This is critical information in formulating a profile of the killer.

Of course if the killer has changed is or her hair color, this evidence could prove misleading.

 

 
5 Comments

Posted by on April 3, 2011 in DNA, High Tech Forensics

 

5 responses to “DNA and Hair Color

  1. Laura Mitchell

    April 3, 2011 at 8:18 am

    Are crime labs set up to do this testing or is this still in the research and development phase?

    Like

     
    • D.P. Lyle, MD

      April 3, 2011 at 8:46 am

      Since it is so new and as yet unconfirmed–meaning that it hasn’t yet been widely confirmed by other scientists and hasn’t been admitted in court as far as I know—it would not be used in most labs–yet. But it will before too long and we’ll see if these results are confirmed and if the courts will accept it. Those are the two essentials for any new forensic science technology to gain acceptance and be widely used. But for fiction, it works right now.

      Like

       
  2. Pat Marinelli

    April 4, 2011 at 9:45 am

    What about cost, Doug? I see on TV shows all these tests for DNA, etc., but with all the budget cuts in today’s economy, who decides what will be done on each crime? Police or budget administrators?

    I wonder if fiction writers down the road will add economy and budgets to thier work to up the conflict. The show Body of Evidence touched on this in the first episode but then by the second it was forgotten.

    Like

     
    • D.P. Lyle, MD

      April 4, 2011 at 10:26 am

      That’s a huge problem and one of the reasons there are serious backlogs for DNA and other work. No money means no equipment and no technicians and things stack up. Investigators want results yesterday, but real life pushes it to next week, or month, or year. Jan Burke’s Crime Lab Project is active in letting the public just how things like budget cuts impact the justice system. Yes fiction writers can use this. Part of creating tension is making it difficult for the hero to get what he needs and delaying the revelation of that knowledge as long as possible.

      Like

       
  3. dr g v rao

    April 5, 2011 at 7:32 pm

    Dear Dr Lyle

    A very good article. Can I have your permission to post the same on my blogsite which is read by many advocates of law in India. My blogsite is http://dna4india.blogspot.com

    with regards

    Dr Rao

    Like

     

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

 
%d bloggers like this: