Police roadside drug test

Step by step

• Stop: paperwork/vehicle check, visual assessment (eyes, speech, smell).
• Pre-test: voluntary breathalyser or saliva strip – result in 5–8 min.
• If suspected: nearest hospital for blood draw by a physician.
• Report to the traffic office and, on criminal suspicion, to the prosecutor.

Swiss practice: procedure, deadlines and costs

A roadside check follows a fixed sequence: first the patrol forms suspicion (driving style, smell, red eyes, speech), then a rapid saliva drug test, usually with Dräger DrugTest or Securetec DrugWipe devices. This pre-test is qualitative, not quantitative — it says "THC detectable", not "how much". If positive, or if the driver refuses, police order a blood draw; it is taken by a physician, as a rule within an hour, and analysed by a forensic medicine institute. The saliva test may be refused, the blood draw ordered by the prosecutor or police may not — refusal is itself punishable (Art. 91a SVG) and treated like a positive finding. It is worth writing down times and the sequence of events right after the check; procedural flaws in the order and the sample chain are the most common line of defence.

The legal limit and the zero-tolerance practice

In Switzerland, a strict zero-tolerance practice regarding tetrahydrocannabinol applies to road traffic. The legally established limit value for the detection of free THC in the blood is 1.5 micrograms per litre. This value represents an analytical detection limit and not a scientifically justified limit for actual unfitness to drive. Anyone who exceeds this value is irrefutably deemed unfit to drive under the law. This means that even hours after consumption, when subjectively no effect is felt anymore, the driving licence can be revoked, as the degradation behavior of THC in the human body varies greatly from person to person.

The determination of the relevant value is carried out exclusively via a blood sample in the laboratory, as saliva tests only provide qualitative indications. During the laboratory analysis, active THC is specifically searched for, while inactive degradation products such as THC carboxylic acid primarily provide information about the frequency of consumption. A high level of degradation products can lead the authorities to doubt the general fitness to drive. In such cases, there is a risk of a medical-psychological assessment, which is ordered independently of the acute incident of driving under the influence of alcohol or drugs and is associated with significant administrative hurdles.

Medical consumption and fitness to drive

Since August 2022, the prescription of medical cannabis in Switzerland has been possible without an exceptional licence from the Federal Office of Public Health (BAG). Doctors can prescribe corresponding preparations directly if there is a medical indication. However, this facilitation in daily medical practice does not exempt patients from the strict rules of the Road Traffic Act. Even for individuals with a valid prescription, the limit of 1.5 micrograms of THC per litre of blood generally applies in road traffic, unless there is an explicit, case-by-case approved exceptional licence or an officially recognised adjustment phase.

Anyone who consumes medical cannabis must be aware of the legal risks during a police check. At the roadside, the police do not primarily distinguish between medical and non-medical use, as road safety is the priority. Patients should therefore always carry a medical certificate or a corresponding prescription to be able to prove the origin of the active substance in an emergency. Nevertheless, this document does not automatically protect against a blood test or the provisional suspension of the driving licence if signs of unfitness to drive are detected or the limit is exceeded.

Cantonal differences in enforcement and official responsibilities

In Switzerland, the enforcement of the Road Traffic Act is the responsibility of the individual cantons, which can lead to inconsistent practices during checks. While some cantonal police forces use saliva tests comprehensively and systematically as preliminary tests, other forces rely more heavily on classic driving behaviour checks and physical symptoms. The handling of small quantities of cannabis carried in a vehicle also varies. Although the possession of up to ten grams of THC cannabis is exempt from punishment nationwide for adults, the levying of fixed penalty fines of one hundred francs for consumption is enforced with varying degrees of severity depending on the canton.

In addition to the police forces, various authorities are involved in the process. The Federal Office of Public Health (BAG) monitors the legal framework and the ongoing pilot trials for regulated distribution. Swissmedic is responsible for the licensing of cannabis-based medicinal products, while the Federal Food Safety and Veterinary Office (BLV) monitors the regulations for CBD products with less than one percent THC. In the event of suspected poisoning or overdose in the context of mixed consumption, Tox Info Suisse serves as the central contact point for initial medical information and risk assessments under the emergency number 145.

Typical mistakes during police checks and correct behaviour

During a traffic check, many people make the mistake of making ill-considered statements out of nervousness or the urge to justify themselves. Statements regarding past consumption behaviour, even if it was days ago, are recorded in the report and can be used directly as reasonable suspicion for a blood draw. The right to remain silent is a central pillar of the Swiss rule of law. Drivers are only obliged to provide their personal details and to present their driving licence and vehicle documents. Active duties to cooperate only exist for legally prescribed measures, but not for voluntary lifestyle questioning.

Another common mistake is the assumption that a negative feeling regarding fitness to drive overrides the limit. Even those who feel completely fit to drive can exceed the limit of 1.5 micrograms of THC per litre of blood. Cooperative but firm behaviour is advisable. Polite restraint when questioned about consumption protects against self-incrimination. If the police order a blood sample, this must be complied with to prevent prosecution for refusal. It is recommended to immediately write down a memory protocol of the exact timeline and the statements of the officers after the check.

Does the THC limit of 1.5 µg/L of blood also apply to participants in Swiss cannabis pilot trials?

Yes, the legal limit of 1.5 micrograms of THC per litre of blood also applies without exception to all participants in the government-approved pilot trials. Although temporary projects such as Züri Can or Weed Care Basel legalise purchase and consumption in a private setting, they do not override the strict rules of the Road Traffic Act. Anyone participating in road traffic must be fit to drive and must not exceed the limit; otherwise, they face the standard criminal and administrative consequences, up to and including the revocation of their driving licence.

How do the police distinguish between legal CBD and illegal THC cannabis during a check?

At the roadside, the police cannot reliably distinguish between legal CBD and illegal THC cannabis by mere visual or olfactory inspection. Since CBD products in Switzerland must have a total THC content of under one percent to not be classified as narcotics, only a laboratory analysis or a specific rapid test can provide clarity. CBD consumers should carry proof of purchase or laboratory certificates to refute suspicion of illegal consumption, as CBD products can also contain small amounts of THC that are detectable in the blood.

What penalty do adults face for consuming THC cannabis outside of road traffic?

In Switzerland, the consumption of THC cannabis by adults is generally punished with a fixed penalty fine of one hundred francs, provided no other offences have been committed. Possession of up to ten grams of THC cannabis for personal consumption is exempt from punishment and does not lead to a fine, provided the cannabis is not actively consumed. However, the cantons enforce these regulations with varying degrees of severity, which is why the practice when encountering consumers in public spaces can vary depending on the region.

Can a positive saliva test lead directly to a permanent revocation of the driving licence?

No, a positive saliva test does not lead directly and without further procedural steps to a permanent revocation of the driving licence. The saliva test merely serves the police as a qualitative preliminary test to establish an initial suspicion at the roadside. For legal consequences such as a criminal complaint or the revocation of the licence, the result of the quantitative blood sample in the laboratory is strictly required. However, following a positive preliminary test, the driving licence is usually confiscated as a precautionary measure until the final laboratory result is available.

Frequently asked questions

Do I have to answer consumption questions?

No. You have the right to remain silent. Providing ID is required, statements about consumption are not.

May I refuse the saliva test?

Yes, the pre-test can be refused. The ordered blood draw cannot — refusing it is punishable under Art. 91a SVG and treated like a positive finding.