Ed
Yong has written a great
blog on this!
http://scienceblogs.com/notrocketscience/2010/03/bacteria_on_your_keyboard_could_suggest_your_identity_but_fo.php Some excerpts:
Just 13% of the bacteria on my palm
also live on yours, and even identical twins can harbour very different microbes. Even after we give our hands a good wash, our individual communities eventually bounce back with a similar mix of members. Skin bacteria are also easy to dislodge. As we go about our daily lives, we leave a trail of our own personal bacteria on the things we touch, which can stick around for days or weeks.
It's a promising technique, but David Foran, director of Michigan State University's Forensic Biology Laboratory, says that it's "utility in a forensic context is doubtful". It's unlikely to ever meet the high standards of certainty needed for a criminal investigation, although that probably won't stop it from appearing in a future episode of CSI.
The problem is that forensics requires a far higher threshold of certainty than skin bacteria are likely to provide. Foran notes that if a fingerprint is a 90% match to a questioned print, a forensic scientist would conclude that that person didn't leave the print. Likewise, a DNA sample that's 10% different would be a negative result, although in that case, you might look for a relative. He says, "The method presented will probably never lead to a match; given the huge amount of bacterial variability the authors find over time and even among different body parts, finding a true DNA match between questioned and knowns would be next to impossible. It would be far easier for the defense to argue that the suspect did NOT leave that bacterial profile."