Why is the use of DNA fingerprinting considered more accurate than reliance on analysis of hair samples?

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DNA fingerprinting, or sequencing, is considered more reliable than analysis of hair samples for the simple reason that it constitutes a more holistic approach to evidence analysis and, in fact, analysis of hair samples is but one component of fingerprinting.

Hair samples can provide important physical evidence of an individual’s connection to a crime.  However, as the recent revelation that the Federal Bureau of Investigation’s process for analyzing hair samples may have been seriously flawed – with the resulting status of thousands of criminal convictions suddenly cast into doubt -- the danger of overreliance on hair in the conduct of criminal investigations and prosecutions can be damaging to the nation’s criminal justice system.

Strands of hair are not necessarily reliable sources of DNA.  Whether the hair samples include pristine traces of the protein keratin, for example, which is present at the scalp but not further along the length of a strand, can determine whether the samples in question provide clues to the identity of a suspect.  DNA sequencing, on the other hand, involves a more detailed and protracted process of testing and analyzing physical evidence, whether from hair, blood, semen, saliva, or skin.  DNA sequencing requires viable cells in order to be conducted, and hair samples may not prove sufficiently reliable.  Sequencing, or fingerprinting, that involves properly collected and preserved DNA from bodily fluids is considered much more reliable than DNA evidence attained from strands of hair.  


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