Because of the ongoing interest in the Ramsey case, Bode Technology’s success in using a Touch DNA collection method to obtain a DNA profile from the long johns worn by JonBenet Ramsey, created an increased interest in better understanding what Touch DNA is and how it works.
Touch DNA is Not LCN DNA
Firstly, it is important to establish that Touch DNA is not Low Copy Number (LCN) DNA. LCN DNA profiling allows a very small amount of DNA to be analyzed, from as little as 5 to 20 cells.
According to Bode, Touch DNA samples are processed/amplified exactly the same way as blood, semen, saliva etc, and can stand up to scrutiny in court much better than LCN DNA.
Bode Technologies – Leading Crime Laboratory
Bode has completed more than 40,000 forensic cases in the past eight years. Among their specialties are cold cases and forensic cases where DNA evidence may be highly compromised.
So What is Touch DNA?
Touch DNA has to do with skin cells. Humans shed tens of thousands of skin cells each day, and these cells are transferred to every surface with which human skin comes into contact.
Locard's Exchange Principle states that with contact between two items, there will always be an exchange. So, when a crime is committed, if the perpetrator deposits a sufficient number of skin cells on an item at the scene, and that item is collected as possible evidence, Touch DNA analysis may be able to link the perpetrator to the crime scene, by collecting the skin cells and analyzing them.
According to the experts, Touch DNA has been successfully sampled from a variety of items including gun grips, steering wheels, eating utensils, luggage handles, and clothing.
More Difficult to Obtain DNA Profiles
Touch DNA is usually not visible and since it is often deposited in smaller amounts than the DNA found in bloodstains or other body fluids, it is more difficult to obtain DNA profiles from these samples.
Collection Method of Touch DNA
The key to obtaining successful Touch DNA results depends on recognizing items which may be suitable for Touch DNA analysis and using the sampling technique or collection method that will recover the highest number of skin cells.
- Swabbing - the surface of the item is rubbed with a cotton swab to collect possible cells. This method is preferred for hard items such as glass or plastic.
- Cutting - may be used for soft items, such as clothing, in which fabric from areas of interest is cut to collect possible cells.
In addition to the commonly used swabbing and cutting methods, Bode Technologies has recently started using the “Scraping” and “Tape Lift” methods, in which the surface of soft items (such as clothing) are either scraped with a blade, or sampled with a small piece of tape, to collect possible cells.
JonBenet Ramsey Case
In this case, the new DNA was recovered by guessing where JonBenet's killer might have handled the long johns she was wearing.
"It's not a stain, you can't see it," said Angela Williamson, director of forensic casework at Bode Technology Group in Lorton, Virginia who led the work on JonBenet's Touch DNA.
DNA from two sites on the long johns matched genetic material from the same unknown male that had previously been recovered from blood in JonBenet's underpants. The matching DNA from three places on two articles of JonBenet's clothing convinced the district attorney that it belonged to the killer, and hadn't been left accidentally by a third party. The DA excluded the parents.
John and Patricia Ramsey found their daughter's body in the basement of the family's home in Boulder, Colorado, on Dec. 26, 1996. The child beauty queen was six and had been strangled.
Sources:
Bode Technologies
Karen Lotter - Karen Lotter is a journalist and writer based in Durban, South Africa. She has written profiles, features, advertising copy, ...
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