What is "touch" DNA? According to an article at the Forensic Science website,
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.The new "touch" DNA was in fact better than the old partial sample taken from the victim's blood. For one thing, it was associated with a particular type of cell, skin cells. For another it contained, apparently, a full set of 13 markers. What's more, both samples matched the old blood sample, providing three different places that the source apparently touched.
Sounds convincing, yes. And to someone such as DA Mary Lacy, mesmerized by the DNA "evidence," it was more than enough to convince her that this was indeed the DNA of JonBenet's attacker and that John and Patsy Ramsey must both be innocent.
Not so fast. Remember the words I've already quoted, of leading DNA specialist Ros Hammond:
"It's not just the finding of the evidence. It's how did it get there, and can we rule out any other way it did so? And what does it mean?"
To understand the DNA evidence, it's essential to keep in mind all the many different ways DNA can be transferred and to remind ourselves that a DNA match between a human and an object does not "necessarily prove they were actually in direct contact at all" (see quotation in previous post). What made me suspicious of this so-called "evidence" from the start was how incredibly sparse it was. If an intruder had actually attacked JonBenet with bare hands, then his DNA would be all over her body and her clothing, not to mention the "garotte" he used to strangle her. The complex, sophisticated methods used to produce miniscule traces of blood and "touch" DNA should not have been necessary. The DNA should have been evident from the start, using conventional methods. And if the attacker used gloves, then there would have been no DNA at all, certainly no touch DNA.
The fact that the DNA that was found was present in such small amounts tells us that, in all likelihood, it was either the result of an indirect transfer or came from a very old contact. Think of all the many ways in which JonBenet might have touched or been touched by someone -- a teacher, a classmate, a casual acquaintance. Think also of all the ways an indirect contact could have been made -- via a water fountain, a toy, a fall on a sidewalk or a mound of dirt, etc., etc. Once this got on her hands it could easily have been transferred to any part of her body, and certainly to her panties and longjohns.
The exotic and painstaking methods used to extract partial strands of DNA from blood, or "touch" DNA from some fabric that might contain only a handful of skin cells are meaningful only if there is already a viable suspect or set of possible suspects to test. And if in fact a match is found, then that would certainly suggest that this person might have been in contact with the victim. Though a lawyer could certainly argue for an indirect, and thus meaningless, connection. In cases where semen is found, and DNA from the semen can be matched with a suspect, that of course is a very different story. But in the Ramsey case no semen was found. In fact the body had been very thoroughly wiped down.
In sum, the DNA evidence -- all of it -- means nothing. A real intruder would have left all sorts of signs of his presence, including gobs of DNA (unless he was wearing gloves), and a real intruder, as I've already argued, would not have done all the things this intruder is supposed to have done. This DNA, like all the other "intruder evidence," is simply one more red herring to be added to all the rest in a long long story of obfuscation, delusion and denial.