2. Sample collection

Hair sampling must be carried out by a competent person (biologist, police officer, gendarme) who carefully follows legal procedures and avoids any contamination of the sample or contact with the substances to be investigated.

It is advisable to wait at least four weeks after possible exposure to the molecule before taking hair samples if the person is alive.

Hair is generally taken from the posterior vertex of the head, as this area shows less variation in growth. The quantity of hair required for analysis is a tuft of hair the diameter of a pencil (i.e. around one hundred hairs). It is important to collect enough hair to enable routine tests to be carried out, as well as a repeat analysis or second opinion if required. In the case of forensic testing, it is advisable to take a duplicate sample. Indeed, when a preliminary screening technique...