Forensic Toxicology and Chemistry Unit


1. What type of biological sample is required to detect possible drug use ?

Detection of the consumption of a drug or a medicine is preferably carried out by analysis of urine if the consumption dates from several hours to several days previously.

If consumption is regular over a period of several days to several months, consumption of the drug can be detected by hair analysis.

Analysis of a blood sample reveals evidence of recent consumption of a drug and allows the patient’s clinical condition to be evaluated at the time the sample was taken.

In addition, regardless of circumstances, we recommend that a sample of at least 10ml of urine and 10ml of blood should be taken from living persons as soon as possible after the event.

2. For how long can the presence of a substance be detected in biological samples ?

The time for which the presence of a substance can be detected in the blood and urine depends greatly on the nature of the substance consumed, the toxicological history of the patient and the individual’s genetic parameters, as well as the sensitivity of test methods used to detect consumed substances.

Generally, the presence of an exogenous substance can be revealed in the blood for around one day after consumption, and for up to three or four days in urine. With regard to hair, the detection time depends above all on the length of the hair.

3. Must a result obtained by an immunological method (screening, rapid test) be confirmed by an additional analytical technique ?

A positive result obtained by an immunological test will necessarily have to be confirmed by an independent method that is very sensitive and characterized by a high degree of specificity.

(For technicians)

The generally recommended method in forensic toxicology is gas chromatography coupled with mass spectrometry, or liquid chromatography coupled with mass spectrometry.

4. Who can request a toxicological analysis ?

Requests for toxicological analyses received by the UTCF come from magistrates, doctors, pharmacists, veterinarians, chemists, the police and other institutions.

Requests for private tests are sometimes formulated through the intermediary of the consulting physician or pharmacist. All requests must be made by post.

The cost and delivery time of tests may be indicated in specific cases on request.