Drug Driving in Spain: Influence vs. Presence (Art. 379.2 CP)

Testing positive for drugs 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 mere presence of the substance in your body; it punishes driving under the influence of toxic drugs, narcotics or psychotropic substances, that is, with your ability to drive actually impaired. This distinction — between having a drug in your system and being impaired at the wheel — is the legal heart of these cases and the backbone of any defence. Below we explain what the offence actually requires, why a positive test is not the same as influence, how impairment is proven, how it differs from a simple traffic file and which lines of defence we examine. You can read more on our page about driving under the influence of drugs.

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

Why 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 a drug 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: the active substance remains detectable long after the psychoactive effect has worn off. In habitual users, the drug 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 soberly. 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? The court weighs 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:

Route	What is punished	Consequence
Administrative penalty	The mere presence of the drug in the body (testing positive)	Fine and loss of licence points, no criminal record
Criminal offence (Art. 379.2 CP)	Driving under the influence: actual impairment of the driving	Prison, fine or community service + disqualification and a criminal record

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 offence requires. The line between the two routes decides whether the person ends up with a criminal record.

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:

• Prison of 3 to 6 months, or
• Fine of 6 to 12 months, or
• Community service of 31 to 90 days, and
• In every case, disqualification from driving motor vehicles and mopeds for more than 1 year and up to 4 years.

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. Where the disqualification exceeds two years, it also entails the loss of validity of the licence, so the driver has to sit the test again.

Refusing the test: the offence under Article 383 CP

At a checkpoint, some drivers believe that refusing the drug test is the "smart" move: with no substance measured, they reason, there is no evidence. It is exactly the opposite. Refusing to take the tests legally required by an officer is a separate offence, that of Article 383 CP, punished with prison of six months to one year and disqualification from driving for more than one year and up to four years.

Its penalty is usually heavier than that of Article 379.2 CP itself, and it does not allow a fine as an alternative to prison. It is also complete on the refusal alone, regardless of whether any influence is later measured. For the offence to exist, however, the request must be lawful and the driver must have been informed of the duty to take the test and of the criminal consequences of refusing. Refusing, in short, does not reduce liability: it increases it.

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 the substance remains detectable after the effect has worn off, especially in habitual users, so that a positive result does not equate to impaired driving.
• Chain of custody and confirmatory analysis: check whether the testing procedure was correct, whether the confirmatory blood analysis was offered, and the integrity of the chain of custody of the samples relating to the active substance.
• False positives from prescribed medication: certain medicines can alter the result of the rapid test; the laboratory analysis and the medical prescription allow them to be ruled out.
• Redirecting to 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.

Specialist criminal defence in road-safety cases

If you are facing a charge of driving under the influence of drugs, it pays to act early and to start from the correct facts, not from the mistaken idea that a positive test is "a sure conviction". Studying the police report, the information given at the stop and the confirmatory analysis usually marks the difference between the offence and a mere fine.

Alonso Sala is a firm dedicated exclusively to criminal law, based at calle Velázquez 27 in Madrid and covering the whole of Spain. We analyse each traffic stop and the proof of influence before taking any defence or guilty-plea decision.