Dirty Fingertips May Leave Forensic Clue

As we all know, bacteria are found practically anywhere including our hands and the things that we touch. A study published in March 2010 by Noah Fierer and his team suggests that bacteria from a person’s hands could one day be used to accurately identify that individual. If this is true, we will be able to track down criminals who remove their fingerprints and/or leave no DNA evidences (such as saliva, tissue, blood, or semen) from the bacteria trail they leave on the objects they touch. Fierer says that a human hand can contain up to 100 different species of bacteria and only ~13% of the same makeup is shared between any two individuals.

Fierer and colleagues did a test to see whether bacteria on an object are more similar to the bacteria found on the owner’s skin than to bacteria on the general population. They compared bacteria sequences found on 9 computer mice to bacteria collected from the hands of 270 individuals. The results suggest that bacteria from each mouse closely matched those from the owner’s hands. Fierer says that this technique was 70% - 90% accurate overall but the percentage could increase as the technology becomes more sophisticated.

Although this intervention attracts many interests, there are limitations of this technology. For example, a professor from Stanford University, David A. Relman, says that it isn’t possible yet to separate mixed-up bacterial trails when more than one person touches the same object. Also, there could be changes to the distribution of bacteria once they left the human hand, thus making it harder to link the microbes to a person.

Personally, I think DNA evidences are more reliable than this technique especially since we already have a large database which we can use to crosscheck the DNA we find on a crime scene. The bacterial trails technique, in the other hand, requires us to have a sample from the suspect whom may not be identified yet.




Fierer, N., Lauber, C. L., Zhou, N., McDonald, D., Costello, E. K., & Knight, R. (2010). Forensic identification using skin bacterial communities. PNAS , 6477-6481.
Khan, A. (2010, March 16). Bacterial trail may be next forensic clue. Retrieved May 26, 2010, from LA Times: http://www.latimes.com/news/science/la-sci-bacteria16-2010mar16,0,5990278.story