Forensic analysts are currently using lasers to analyze hair samples at crime scenes or for drug testing. Lasers are being used in these tests to burn the hair samples, which create hair fumes. The fumes are sent into a mass spectrometer to determine which elements and isotopes are present in the hair. This measurement can actually be used to extract information about the person from whom the hair originated (the hair donor). Analysts can learn what the hair donor ate recently, and also what drugs the donor may have been using, since traces of drugs like the htc in marijuana can be detected in hair follicles for several months or even years after smoking.
Lasers are being used to burn the hair samples, but a new method of laser hair analysis has been developed that can give even more information than the previous method. An article at Physorg.com states that "traditional laser analysis techniques tended to obliterate entire samples as they burned all of its parts together as a whole." This essentially eliminates the ability for analysts to determine exactly when the hair donor ate something or used a particular drug. However, the article reports that a team of researchers have made some improvements to the technology:
"Moran and his team chose to use a less destructive type of laser that uses only ultraviolet light (similar to the kind used for LASIK eye corrective surgery). They discovered that by doing so they could essentially break apart the individual pieces and parts of the hair as a hole was bored, which could then be burned separately and tested with the spectrometer; sort of like burning the filings left over when drilling into a piece of wood with an iron bit. Because hair grows slowly over time, it creates a timeline of sorts, with different stages representing differing days, weeks or even months."Holes can be bored down the length of the hair and the fumes from each hole analyzed separately. Thus, timings of events can be determined accurately, whereas before the hair donor's history involved a lot of guesswork and estimations.