Forensic Toxicology and Chemistry Unit


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

Drug testing is best done through urine analysis if drug use has been occurring for a few hours to a few days.

If drug use is regular, lasting from a few days to a few months, drug testing is done through hair analysis.

A blood sample can be used to identify recent drug use and to assess the patient's clinical status at the time the sample is taken.

In addition, we recommend that a minimum of 10 ml of urine and 10 ml of blood be collected from living individuals promptly after the event, regardless of the circumstances.

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

The time during which the presence of a substance can be detected in blood and urine depends strongly on the nature of the substance consumed, the toxicological experience of the patient, the genetic parameters of the individual, as well as the sensitivity of the analytical techniques used to detect the consumed substances.

In general, the presence of an exogenous substance can be detected in the blood for about 1 day after consumption and up to 3-4 days in the urine. As far as hair is concerned, the detection time depends primarily 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 must necessarily be confirmed by an independent method, very sensitive and characterized by a very high degree of specificity.

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

4. Who can request a toxicological analysis ?

The requests for toxicological analysis received by the CTU come from magistrates, doctors, pharmacists, veterinarians, drug dealers, police, as well as from other institutions.

Private requests for analysis are sometimes made through the attending physician or pharmacist. All requests must be made in writing.

On request, the cost and time of the analyses can be indicated for a specific case.