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Estimating Age From Crime Scene Blood

26 Nov

The police are called to a suspected crime scene, one where a murder has likely taken place. There is no body. There is no suspect. There are no witnesses. But a large blood stain is found at the scene. Whose blood is it?


Any police investigator will tell you that identifying victim is one of the first and most important steps in identifying the perpetrator. The simple reason is that most murders are committed by someone with some relationship to victim. A spouse, a friend, a coworker. But without a corpse, how can the victim be identified?

Since in this circumstance there would be no description of victim, the police would not know where to look. They would have no age, sex, size and weight, height, or any of the other physical details that might narrow their search for who the victim might be. Each one of these factors can help narrow the possibilities.

But what if they could determine that the victim was a teenager or a middle-aged male or an elderly female? DNA obtained from the blood could easily determine the sex but not the age of the victim. Until now. There appears to be a new test that just might reveal age from a crime scene blood sample. And least in broad terms.

A recent report in the journal Current Biology submitted by researchers from the Erasmus MC University Medical Center in Rotterdam, Netherlands suggests that byproducts from human T cells might supply this information. It’s complex biology but it seems that our T cells, which are an important component of our immune system, have great diversity in their receptors. It is these receptors that allow them to recognize a multitude of foreign invaders and tag them for destruction by the white blood cells and other components in the complex system that protects us from infections.

It seems that this diversity is accomplished through a constant rearrangement of the DNA within the T cells. A byproduct of this process is the creation of small circular DNA molecules known as Signal Joint TCR Excision Circles, or sjTRECs for short. It appears that the amount of these DNA packets declines at a constant rate with age. Using them, these researchers believe that they can narrow the age range of the person who shed the blood to within 20 years. Not very accurate but it would distinguish a teenager from a middle-aged person or an elderly individual and this in turn might help identify the victim.

Stay tuned. This could prove to be an interesting and useful technique. Or not.

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2 responses to “Estimating Age From Crime Scene Blood

  1. Patti Shinners

    November 26, 2010 at 6:55 pm

    Interesting info about determining age using T-cells. Would a person’s physical condition interfere with that — say someone with an autoimmune disease such as HIV where the T-cells are compromised or someone with a chronic condition that stressed the immune system?

     
    • D.P. Lyle, MD

      November 27, 2010 at 9:03 am

      Interesting point and I don’t know the answer. I would suspect that the declining T Cell counts in HIV would alter this determination greatly and probably enough to make it not very useful. But I don’t know for sure. This technique is so new it’s possible that no one knows yet.

       

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