According to the decision of the Constitutional Court, ref. no. Up-290/20-21, U-I-138/24-6, dated October 2, 2025 (hereinafter: the Constitutional Court’s decision), it follows that an indicator is not a (technically appropriate and technically reliable) measuring device, but rather a means for the rapid detection of alcohol in exhaled air, therefore, the result of the indicator test is considered a correct and valid basis for establishing the commission of the offense of driving under the influence of alcohol or for imposing sanctions under Article 105 of the Road Traffic Rules Act (hereinafter: ZPrCP) only if the person being tested agrees with this result and confirms it by signing the report. Otherwise, the police officer must order the person being tested to undergo a breathalyzer test or a medical examination—that is, a reliable method of detecting the presence of alcohol—which may lead to a different result, including one that is more favorable to the person being tested. The alcohol indicator test, therefore, has no evidentiary value in and of itself, and consequently, the assessment of intoxication is based solely on the offender’s agreement with the test result. After conducting a breathalyzer test that indicates a blood alcohol concentration exceeding the legal limit, and before the offender signs the breathalyzer test report, the police must provide procedural guarantees. Such action by the police is required by both Article 29 of the Constitution of the Republic of Slovenia (hereinafter: URS) and the Minor Offenses Act (hereinafter: ZP-1) in the fourth indent of the first paragraph of Article 67 in conjunction with the fourth paragraph of Article 148 of the Criminal Procedure Act (hereinafter: ZKP). To determine the moment when the offender must be informed in accordance with Article 55 of the ZP-1 or Article 29 of the URS, the key question is when a traffic control matter escalates into a misdemeanor case, since from that moment onward, due to the punitive nature of the proceedings, the offender has different rights. This moment can be defined by focusing the suspicion of an offense on a specific offender with a standard of proof corresponding to the grounds for suspecting that the person committed the offense. This standard can undoubtedly be met during an alcohol indicator test when the indicator shows the presence of alcohol. By doing so, the person being checked has entered the status of a suspected offender in the proceedings and has also acquired new rights. The right to make a statement also includes the right to remain silent and the privilege against self-incrimination, thereby ensuring a level of constitutional legal protection in criminal proceedings.

It further follows from the cited decision of the Constitutional Court that experts point out that the devices used in practice for testing under the second paragraph of Article 107 of the ZPrCP operate on a different, less reliable principle than breathalyzers and do not meet the essential technical requirements which are established for breathalyzers to ensure the reliability of results (such as requirements regarding the number of sensors, the number of required breaths, self-checks, detection of oral alcohol, detection of influencing substances, and software protection). A test using such a device may therefore yield a false-negative or false-positive result. For the reasons stated, the result of a test with an indicator—unlike the result of a breathalyzer test and the result of a professional examination — cannot, on its own, be sufficient to establish that the subject had more alcohol in their system than permitted by law and that they thereby met the legal criteria for an offense (or that the blood alcohol level reached the threshold at which a stricter penalty is imposed on the offender).

It also follows from the cited decision of the Constitutional Court that the Constitutional Court found the second paragraph of Article 107 of the ZPrCP to be inconsistent with the URS, since a positive result of an alcohol indicator test and the subject’s agreement with that result do not satisfy the constitutional standard of proof required for a conviction for a misdemeanor. The second paragraph of Article 107 of the ZPrCP—which, in the event that the subject agrees with the positive test result, does not provide for the conduct of additional reliable tests, thereby indicating that the level of intoxication has been sufficiently established —therefore infringes upon the presumption of innocence under Article 27 of the Constitution. The court noted that the subject’s statement agreeing with the positive result of the breathalyzer test could have been relevant as evidence if the subject had known the alcohol concentration in his body before being shown the result of the breathalyzer test. However, it must be taken into account that this concentration depends on numerous factors—gender, age, body weight, tolerance to alcohol, the quantity and type of alcoholic beverage, the manner of consumption, the time elapsed since consumption, food consumed beforehand, etc. It is impossible for an individual to be fully aware of all these circumstances, to properly balance them, and, taking all these factors into account, to know what the exact result of their alcohol test should be. Thus, no one is able to confirm that a positive result is correct. It is therefore impossible to provide such a precise estimate of alcohol concentration as is required for imposing a sanction under Article 105 of the ZPrCP—i.e., accurate to the second decimal place of milligrams of alcohol per liter of exhaled air. An individual, therefore, cannot, solely through their own behavior and knowledge (without the use of reliable technical devices), lend the necessary credibility to a positive result from a breathalyzer test.

The Constitutional Court’s decision clearly sets limits on the use of alcohol indicators in misdemeanor proceedings. As unreliable and merely indicative tools, such indicators cannot in and of themselves constitute sufficient evidence to establish the offense of driving under the influence of alcohol, and certainly not to impose sanctions. Therefore, for constitutionally compliant decision-making, it is essential to use more reliable methods, such as breathalyzers or expert examinations, which alone can ensure adequate evidentiary value and respect for the presumption of innocence. The National Assembly must remedy the identified inconsistency (second paragraph of Article 107 of the ZPrCP) within one year of the publication of the Constitutional Court’s decision in the Official Gazette of the Republic of Slovenia. Until the identified inconsistency is remedied, the second paragraph of Article 107 of the ZPrCP shall continue to apply.