Segmental Hair Analysis
Definition
The practice of cutting a hair strand into consecutive segments (typically 1 cm each) and analysing each segment separately. Because hair grows at roughly 1 cm per month, each segment represents approximately one month of systemic exposure, allowing a timeline of drug or toxin use to be reconstructed.
- Segment length
- Typically 1 cm consecutive lengths
- Growth rate assumption
- Roughly 1 cm per month
- Purpose
- Reconstruct a timeline of drug or toxin exposure
Common questions
Why is segmental hair analysis useful in chronic poisoning cases specifically?+
It can show whether a toxin was present continuously across many months, consistent with chronic dosing, versus appearing in only one or two segments, consistent with a single acute exposure, which shapes how a case is interpreted.
Does hair length limit how far back the technique can look?+
Yes, the analysis can only cover the exposure window represented by the collected hair length, so a short haircut close to the scalp limits how far into the past the profile can extend.
Related terms
- Anagen Phase
- The actively growing phase of the hair follicle, during which the keratinocyte is in contact with the dermal papilla capillary and incorporates...
- External Contamination
- The presence of a drug or substance on the outer surface of the hair shaft from environmental exposure rather than systemic ingestion....
- Hair Shaft Cortex
- The main structural layer of the hair shaft, composed of tightly packed keratin filaments. It contains the melanin granules responsible for hair...
- Mitochondrial DNA (mtDNA)
- DNA located in mitochondria rather than the cell nucleus. Present in hundreds to thousands of copies per cell, making it recoverable from...
- Short Tandem Repeat (STR)
- Short repetitive DNA sequences scattered throughout the genome, with the number of repeats varying between individuals at each locus. DNA profiling compares...