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Last month various news outlets reported that police had used a technique called “touch DNA” to clear the family of JonBenet Ramsey of any wrongdoing in her gruesome 1996 death.
So what’s touch DNA?
The touch DNA method—named for the fact that it analyzes skin cells left behind when assailants touch victims, weapons or something else at a crime scene—has been around for the last five years. In fact, the prosecutor in the Ramsey case, Boulder County District Attorney Mary Lacy, learned about touch DNA when she attended a course here at the West Virginia University Forensic Science Initiative in the summer of 2007.
The technique has dramatically increased the number of items of evidence that can be used for DNA detection. In the 1980s, in order to perform DNA analysis on a crime scene or victim, forensic investigators needed a blood or semen stain about the size of a quarter. The sample size fell in the 1990s to the size of a dime and then became: “If you can see it, you can analyze it.”
Touch DNA doesn’t require you to see anything, or any blood or semen at all. It only requires seven or eight cells from the outermost layer of our skin.
Here’s how it works: Investigators recover cells from the scene, then use a process called polymerase chain reaction (PCR) to make lots of copies of the genes. Next, scientists mix in fluorescent compounds that attach themselves to 13 specific locations on the DNA and give a highly specific genetic portrait of that person. The whole process takes a few days, and forensic labs are often backed up analyzing data from other cases.
These 13 locations were carefully chosen because they are highly variable between people and do not give away any specific information, such as race, gender, personal health or genetic disease. The reason: authorities don’t want personal health information being used for law-enforcement purposes, such as interrogations. The chance of DNA profiles from two different people having the same genetic signature is vanishingly small.
The trick to finding these cells: context. If clothing is removed from the victim, as it was in the Ramsey case, a forensic specialist could try to guess where it might have been handled—perhaps the waistband of a pair of pants—and swab those areas with a Q-tip or a blade. But in cases like the JonBenet Ramsey murder, which has tripped up authorities for over a decade, it can provide information that leads to a killer—or at least exonerates the innocent.
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16 Comments
Add CommentThe DNA evidence did not clear the Ramsey family, but did indicate that there was a person other than a family member who was apparently involved.
Reply | Report Abuse | Link to thisHow stupid! They guessed where the murderer might have touched, when they know the murderer touched the garrote.
Reply | Report Abuse | Link to thisStevepom,
Reply | Report Abuse | Link to thisNot necessarily on possibly idicating an outsider.
Touch DNA could have come from a factory worker who made the garment or a shopper who picked it up.
You are correct, that the DNA evidence should not clear the Ramsey family.
I think it is the reverse: touch DNA would clear someone if no evidence of their DNA could be found, but it would not necessarily convict someone - that factory worker, for example.
Reply | Report Abuse | Link to thisI^mz .... I = infinite ^ angle of mz = largest and smalles measurement programmed ga programming
Reply | Report Abuse | Link to thisRe: "The chance of DNA profiles from two different people having the same genetic signature is vanishingly small." Google "arizona dna", for example: http://www.latimes.com/news/local/la-me-dna20-2008jul20,0,1506170,full.story
Reply | Report Abuse | Link to thisI just thought about an interesting thing on the confession and arrest of John Mark Karr.
Reply | Report Abuse | Link to thisSuppose, Mary Lacy decided to charge John Mark Karr with the murder of Jonbenet Ramsey, and it goes to a trial, and upon entering his plea, Karr pleads GUILTY!
Karr is then convicted of a murder he did not commit, and the case is closed! No plea bargain, no real trial, and the conviction is based on a phony confession that is full of holes!
Can it happen????? I am not sure, but it sure isn't funny!
****************
Now, how about THIS scenario?
John Mark Karr confesses, he is extradited to Boulder Colorado, and the results of the DNA tests MATCH! (Of course, this is hypothetical.)
Now the kicker. Karr retracts his confession, and says he did not commit the crime in spite of the "touch DNA evidence".... Do we get a conviction? MAYBE NOT!!!!! WHY???? Because, the "touch DNA" only proves that he touched one of the pieces of clothing. It does NOT place him at the scene of the crime, and there is no other credible evidence that he was at the scene of the crime! No fingerprints, nothing but the touch DNA which prives that he touched the item ONLY. It does NOT prove that he touched the victim, struck her, and strangled her. It also does NOT prove that he was ever in the Ramsey home!
SO, IF a DNA match is found, how do we attain a conviction without a confession? The answer is "NO WAY!"
Personally, I think the touch DNA came from a factory worker who made the garment.
Depending on the age of the clothing, (how many times it was taken on and off) the chances of the trace dna belonging to a factory worker are slim at best. However, there are many other possibilities of close or even random people who's trace dna could show up, so the particular example they used is fairly defunct, but there could have been other areas they checked - this article could merely have been giving an example, where the *actual* site may have been much more accurate.
Reply | Report Abuse | Link to thisAlso, I believe Johnnyboy was trying to argue against the piece he quoted, but he did quite the opposite for me - I googled exactly what he said and came to this page:
http://dna-view.com/ArizonaMatch.htm
The main thing to look at is the chart in section IIA, which explains the basic theoretical (or expected) matches and how the actual results were only 1.8 times greater - nothing much, especially for a 9-loci match, which is never even considerd. When the test is run, they don't run it on 13 loci and then go "Oh, this one *almost* matched, let's count it!" They look at ALL THIRTEEN loci, which is very rare.
The 1.8 increase in the actual matches could also be explained (and has, by the matematician mentioned in that link) in any number of ways, especially evolutionary favoritism towards particular genes, which is still present even if "they are highly variable between people."
So that's my two cents' worth, penny for your thoughts?
Does anyone know if it is possible for cells from a touched item can contaminate another item by simply coming in contact with it. For example, if an item like a bag is touched by a person so that cells are left on it and that bag comes in contact with a piece of clothing. Can there be transference of cells from the bag to the piece of clothing.
Reply | Report Abuse | Link to thisStaglin,
Reply | Report Abuse | Link to thisThe answer to your question, is yes, it can. However, by simply having an item with touch DNA transferring to another item is minute, and probably not detectable. In the Ramsey case, it is more possible because both items were worn by the victim.
Still, Mary Lacy was quite foolish to exonerate the Ramsey family because of the touch DNA. What she did would have been OK IF they found that touch DNA elsewhere in the house, on the ransom note, or on the garrote.
Touch DNA technology should not be considered as full proof , because it only reveals presence of third person but doesn,t tells exact time of presence.
Reply | Report Abuse | Link to thisThis sounds similar to the "cocaine on banknotes" to me.
Reply | Report Abuse | Link to thisEverybody sheds skin cells, hair cells, etc, spreading their DNA far and wide.
Perhaps somebody should do a Degrees of Separation study to see how vagrant DNA might migrate.
Jandrew is correct on the chances of the touch DNA coming from China being extremely slim. The chances of the touch DNA coming from the murder scene is also extremely slim, because of the time lapse between the crime and the extraction of the touch DNA. Most likely, the TDNA came from someone who touched the long johns when folding it or storing it.
Reply | Report Abuse | Link to thisDizzy. I'm so dizzy, my head is spinning. Like a whirlpool, it never ends. And it's you, girl, making it spin. You're making me dizzy! The first time that I saw you girl I knew that I just had to make you mine. But it's so hard to talk to you with fellas hangin' 'round you all the time. I want you for my sweet pet but you keep playing hard-to-get. Going around in circles all the time. Dizzy. I'm so dizzy, my head is spinnin'. Like a whirlpool, it never ends. And it's you, girl, making it spin. You're making me dizzy! I finally got to talk to you (12/26/'96) and I told you just exactly how I felt. Then I held you close to me and kissed you and my heart began to melt. Girl, you've got control of me, 'cause I'm so dizzy I can't see. I need to call a doctor for some help! Dizzy! I'm so dizzy, my head is spinnin'. Like a whirlpool, it never ends. And it's you, girl, making it spin. You're making me dizzy. My head is spinnin'. Like a whirlpool, it never ends. And it's YOU, girl, making it spin........
Reply | Report Abuse | Link to thisNeither DNA nor computer-enhanced sound analysis of the 911 call made during the party, nor conventional pavement-pounding detective work will ever result in the culprit being convicted. However, not to worry; no one gets away with anything. No one. Not ever. Rest in peace, sweet princess. and hence...
There were SIX different male DNA markers recovered from the cord used for the ligature and her clothing! Are we to believe that six different men were involved in this crime?! Of course not! Mary Lacy was WAY out of line in clearing the guilty parties in this crime! What is it with the DA's office in Boulder? The DNA on the clothing could've come from a factory worker (and most likely did) and the DNA on the cord, if not in a sealed package could've come from anyone at McGuckin's Hardware where Patsy bought it!
Reply | Report Abuse | Link to thisYou say the chances are slim that the DNA could come from a factory worker, however, detectives bought brand new articles and sent them to the lab in the packaging and had them tested and sure enough, male DNA was found on the new items right from the package!
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