Driving Under the Influence of Cannabis: Art. 379.2 CP

Testing positive for cannabis at a roadside checkpoint does not, on its own, mean you have committed a crime. Article 379.2 of the Criminal Code (CP) does not punish the presence of the substance in your body; it punishes driving under the influence of drugs, that is, with your ability to drive actually impaired. This distinction — between having THC in your system and being impaired at the wheel — is the legal heart of these cases and the backbone of any defence. As criminal lawyers focused on cannabis and driving, we explain it below. If what you need is the general framework on cannabis use (at home, in the street, cultivation, clubs), we cover that in our guide Is smoking cannabis legal in Spain?; here we focus exclusively on driving.

What Article 379.2 CP actually says

The provision punishes "anyone who drives a motor vehicle or moped under the influence of toxic drugs, narcotics, psychotropic substances or alcoholic beverages". It then sets an automatic objective threshold, but only for alcohol: driving with a level above 0.60 mg/l of breath or 1.2 g/l of blood is an offence "in every case".

The decisive point is that no such objective threshold exists for drugs. The Criminal Code sets no THC "level" above which driving becomes automatically criminal. For cannabis and other narcotics, the only route to the offence is actual influence: it must be proven that the drug impaired your driving. The mere detection of the substance is therefore not enough.

A positive test is not the same as being under the influence

The roadside test is almost always a saliva test. That test answers one specific question: "is there THC in the saliva?". It does not measure the degree of impairment, nor does it prove the driver was actually affected at the moment of driving. In legal terms it is an indicator of use, not proof of influence.

The reason is pharmacological, and its legal consequences are very clear: THC remains detectable long after the psychoactive effect has worn off. In habitual users, the substance can show up in saliva (and even more so in blood or urine) hours — or longer — after the person stopped feeling any effect at all. In short, you can test positive while driving perfectly sober. That is why the settled case law of the Supreme Court requires, in Article 379.2 CP drug cases, something more than the positive test: proof of actual influence on the driving.

How influence is proven in practice

If the positive test is not enough, what turns the conduct into a crime? Courts weigh the evidence as a whole to decide whether there was real impairment. The usual elements are:

• Outward signs of impairment recorded in the police report: dilated pupils, red eyes, slurred speech, lack of coordination, drowsiness, smell, incoherent behaviour.
• Manner of driving before the stop: weaving, drifting across lanes, inappropriate speed, sudden braking, running signals or, in the worst case, an accident.
• The driver's own statements and, where applicable, any admission of recent use.
• Confirmatory testing: a positive saliva result is usually followed by a confirmatory analysis (often in blood) at an accredited laboratory, with its corresponding chain of custody.

Where there are clear signs of impairment together with erratic driving, the Article 379.2 CP offence is well supported. Where all there is is a positive saliva test, with no signs and no irregular driving, the evidential basis for influence is far weaker.

Criminal offence versus administrative traffic penalty

This is where the most common confusion arises. There are two separate routes that should not be mixed up:

The administrative penalty for testing positive for drugs is set out in the road-traffic legislation (the Spanish Traffic, Vehicle Circulation and Road Safety Act) and operates independently of the criminal process: it punishes the positive result even if no influence is proven. That is why the same stop can end in nothing more than a traffic fine if the prosecution cannot prove the impairment the criminal offence requires.

Penalties under Art. 379.2 CP

Article 379.2 CP refers back to the same penalties as the first paragraph (criminal speeding). They are alternative penalties — the court imposes one of the three — and, in every case, disqualification from driving:

Disqualification is mandatory and is added to whichever of the other three penalties applies. It is worth bearing in mind because, in practice, it is the consequence that most affects the convicted person's daily life. You can read the full text in Article 379 CP.

Lines of defence

The strategy varies from case to case, but in these matters the most effective defences turn on the separation between positive test and influence and on the regularity of the evidence:

• No proven influence: review whether the police report describes real signs of impairment or simply records the positive result. With no signs and no erratic driving, the proof of influence is fragile.
• Detectability versus effect: argue that THC remains detectable after the effect has worn off, especially in habitual users, so that a positive result does not equate to impaired driving.
• Testing procedure: check whether the procedure was correct, whether the confirmatory blood analysis was offered, and the chain of custody of the samples.
• Overall assessment of the evidence: where the only basis is a saliva test, analyse whether it allows a court to conclude, beyond reasonable doubt, that the ability to drive was impaired.
• Fitting it into the administrative route: where the offence is not proven, the conduct can be redirected to the traffic penalty, avoiding a criminal record.

For the other road-safety offences (drink-driving, refusal to take the tests, reckless driving or driving without a licence) you can consult our road safety offences area.