Drug screening while driving: saliva, analysis, and counter-expertise
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First step: saliva screening
Law enforcement generally uses a rapid saliva device to detect several families of drugs. This test provides immediate guidance but does not alone constitute the definitive analysis of the case.
The decree of December 13, 2016, sets minimum detection thresholds for road devices. For cannabis, the threshold for saliva screening is 15 ng/mL of THC.
Second step: sample collection for analysis
When a screening is positive, a sample is taken according to the official procedure to detect and confirm substances by a laboratory analytical method.
This analysis has a different purpose than a self-test: it is part of a regulated procedure, with requirements for sampling, traceability, and identification.
What about blood sampling?
Blood sampling has not simply “disappeared” from the procedure. The driver can request that a sample be reserved for them to allow an expertise or counter-expertise under the conditions provided by the regulations.
The exact process depends on the situation and the actions taken during the check. Documents given by law enforcement must be read carefully.
Does the offense depend on a visible state of impairment?
French law punishes driving after drug use. It is therefore not necessary for the driver to show obvious signs of intoxication or for an impairment level comparable to alcohol to be established.
What are the sanctions in 2026?
Driving after drug use can be punished by three years of imprisonment, a €9,000 fine, and a six-point deduction. In case of combination with alcohol, maximum penalties can reach five years of imprisonment, a €15,000 fine, and nine points deducted.
Other measures may be added: suspension or cancellation of the license, immobilization or confiscation of the vehicle, courses, and additional penalties depending on the case.
Does a self-test reproduce the police check?
No. Even when a test sold to the public detects the same families of substances or shows a comparable threshold, it does not become the official device nor legal proof.
A self-test can support a prevention approach, but a negative result does not guarantee fitness to drive nor the absence of a future positive result during a check.
The safest decisions
- do not drive after consumption;
- plan a sober driver or another transport solution;
- consider medications that may impair alertness;
- do not combine alcohol and drugs;
- never use a self-test to calculate a time to resume driving.
