Criminal Lawyers for Cannabis and Driving

Driving under the influence of cannabis is one of the most commonly prosecuted drug driving offences in Spain. However, it is also one of the most defensible, because THC (the active component of cannabis) remains detectable in the body long after any psychoactive effects have ended. A positive test does not necessarily mean the driver was impaired at the time of driving.

You have tested positive for cannabis at the roadside: what it means and what happens next

A positive roadside saliva test is a screening result, not proof of an offence. Art. 379.2 CP punishes driving under the influence of drugs, and the presence of THC in oral fluid does not by itself establish that influence: cannabis metabolites persist for far longer than any impairing effect. What decides the case is the confirmatory laboratory analysis together with the signs of impairment recorded by the officers — and both are contestable.

What to do (and what not to do) before making a statement

• Do not make a statement without a lawyer of your own choosing. Articles 118 and 520 of the Criminal Procedure Act (LECrim) give you the right to remain silent, not to incriminate yourself and to speak with your lawyer in private before the statement. What is said in the first appearance conditions the whole case.
• Ask for the confirmatory analysis and keep the record of it. The screening device is not the evidence; the laboratory result on the counter-sample is, and requesting it is a right, not an admission.
• Write down what the officers observed and what you were asked to do while it is fresh: the roadside signs of impairment noted in the report are the second half of the prosecution case and they are assessed against your account.
• Weigh up the plea agreement (conformidad) with your lawyer, not in the corridor. In the fast-track route (Arts. 795 ff. LECrim) it is offered at the duty court itself and Art. 801 LECrim reduces the sentence by one third — but once given it cannot be undone, and it is a final conviction with all its consequences.

Legal Framework: Detection vs. Impairment

Driving under the influence of drugs falls under Art. 379.2 CP, the same provision as drink-driving. But THC can be detected in saliva up to 48 hours after consumption, and in blood for even longer, so a recreational user who consumed cannabis the previous evening may test positive the next day while completely sober. The prosecution must prove not just substance presence, but that the driver's faculties were affected at the moment of driving —and, crucially, there is no legally established THC impairment threshold equivalent to the blood-alcohol limits.

Defence Strategies

Our defence centers on: presenting expert toxicology evidence showing that THC levels do not correlate linearly with impairment (unlike alcohol, there is no established THC impairment threshold), demonstrating the absence of clinical signs of impairment (stable driving, normal reaction to police instructions, passing coordination tests), and challenging the time of consumption to show the effects had dissipated before driving.

THC Persistence & Expert Evidence

THC is stored in fatty tissue and released slowly: occasional users can test positive for 2-7 days, and habitual users for two to four weeks or more, long after any psychoactive effect has ended. A private toxicology expert can assess the concentration detected and its correlation with impairment, the consumption window, the reliability of the screening device and the consistency with the external signs in the report —evidence that frequently creates reasonable doubt.

Criminal Consequences

The penalties mirror those of drink-driving: prison of 3 to 6 months (usually suspended for a first offence), a fine of 6 to 12 months, and the deprivation of the right to drive of 1 to 4 years. The defensive position is, however, generally stronger than in alcohol cases: the gap between detection and actual impairment, and the absence of a legal THC threshold, create reasonable doubt that frequently prevents conviction or reduces the matter to an administrative sanction.

Presence versus influence: the line between crime and administrative penalty

The most common mistake in these proceedings is to confuse testing positive with committing a crime. Article 379.2 of the Criminal Code does not punish the mere presence of cannabis in the body; it punishes driving under its influence, meaning with the actual driving capacity genuinely impaired. Cannabis counts as a drug for these purposes, but the substance can remain detectable in saliva long after its effects have worn off. For that reason, a test that picks up traces of THC, on its own and without proven impairment, falls within the administrative infringement of the traffic regulations (RDL 6/2015), not within the criminal offence.

Separating these two planes is the defence's first task. Unlike alcohol, where the legislature fixed objective thresholds (0.60 mg/l in exhaled air or 1.2 g/l in blood) that trigger the offence on the objective limb of article 379.2, with drugs there is no figure that automatically turns a positive into a crime. The prosecution must prove influence through external factors: the manner of driving, the signs detected by officers, slowed reflexes, or the symptoms recorded in the police report. Without that proven influence, the reproach belongs to the administrative sphere and must stay outside the criminal proceedings.

The police report, the fast-track trial and the guilty plea

Road-safety offences are the typical channel for the fast-track trials set out in articles 795 and following of the Criminal Procedure Act. The case begins with the police report, which records the external signs observed, the result of the indicative test and the circumstances of the driving. Investigation falls to the Investigating Court or the Duty Court, while trial and judgment fall to the Criminal Court. The speed of the procedure is an advantage, but also a risk: the pressure to settle quickly can lead to accepting a conviction that a calm review of the evidence would not support.

The guilty plea is a legitimate option and, in some cases, an advantageous one, because it can reduce the sentence under the rules of the Criminal Procedure Act. But it should only be explored after analysing the strength of the evidence: if the saliva test was not confirmed analytically, if the report does not describe real impairment, or if the chain of custody has gaps, pleading guilty may mean giving up an achievable acquittal. The decision to plead or go to trial must be taken with the report and the lab findings in hand, weighing each element, never by the mere inertia of the fast-track process.

Challenging the evidence: the indicative saliva test and lab confirmation

The roadside saliva test carried out by officers is indicative: it detects the possible presence of the substance, but it neither measures a concentration that is meaningful for criminal purposes nor proves, on its own, influence on driving. That is why the regulations require a second sample for analytical confirmation in a laboratory. The defence must verify that this confirmation took place, that the chain of custody of the sample was respected, and that the analysing laboratory met the required conditions. A field positive that is not confirmed in a laboratory is a fragile evidential basis on which a conviction can hardly rest.

Alongside this, the driver has the right to request a blood test as a counter-check, a right that must be notified and respected. Where the case rests on alcohol, the breathalyser must be subject to current metrological control and periodic verification, and the device's error margins should be examined; in the case of speeding under article 379.1, the radar must hold a valid verification and the regulatory error margin must be applied. Reviewing verification expiry dates, certificates and margins is no formality: it is the core of a serious technical defence in road-safety cases.

Penalties, driving disqualification, mitigating factors and the five-year limitation

A conviction under article 379.2 does not end with the principal penalty —imprisonment, a fine or community service, according to the rules of the provision— but specifically carries with it disqualification from driving motor vehicles and mopeds under article 47 of the Criminal Code. That disqualification often has practical consequences more burdensome than the fine itself, especially for those who depend on a vehicle, and its length must be calibrated to the circumstances of the case. It should also not be confused with the administrative loss of licence points, which operates on a separate plane.

Sentencing weighs mitigating and aggravating circumstances: the degree of proven impairment, the driver's cooperation, the absence of concrete risk to third parties or, conversely, reckless driving. As a time anchor, because these offences carry a maximum penalty of no more than five years, they become time-barred after five years under article 131 of the Criminal Code; there is no three-year bracket applicable to these figures. Verifying the limitation calculation, the correct analytical confirmation and the separation from a mere administrative infringement are the three pillars on which the defence strategy is built.