Microscopic Hair Comparison
Definition
A forensic technique in which an examiner visually compares morphological features of hair samples under a microscope. DNA testing has shown that claimed matches are unreliable as proof of common origin; the FBI formally acknowledged this in 2012.
- Method
- Visual morphological comparison under microscope
- Basis
- Subjective, non-statistical assessment
- Reliability for individualisation
- Not supported by DNA-based validation
- Current role
- Screening only, confirmed by mtDNA or nuclear DNA
Common questions
Why did courts once treat hair matches as strong evidence?+
Examiners historically testified to a match in terms implying near-certain individual identification, but no validated statistical basis for that certainty existed; the technique could only support similarity, not a source-attribution probability.
What role, if any, does the technique still play?+
It remains useful as an inexpensive screening step to exclude obviously dissimilar hairs or to select candidate samples, but any inclusion finding now requires confirmation by DNA testing before it carries evidentiary weight.
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