A report came in that a car was standing in the middle of the road with its engine running and a man asleep in the driver's seat. It happened in Sejong City in December 2023. The police officers who were dispatched arrested him as a flagrant offender and took him to the police box, where a breath test showed a blood alcohol concentration of 0.081%. Indicted for driving about 3 km while drunk, he had already received a summary order imposing a fine of 1 million won for drunk driving in 2019. The first and second instance courts sentenced him to one year of imprisonment, suspended for two years.
Yet according to a Money Today report, the First Division of the Supreme Court reversed the judgment and remanded the case to the lower court. The reason, surprisingly, was a single glass of water. Because the police did not give him water to rinse his mouth before the test, the test result was evidence obtained illegally and, absent special circumstances, could not be used as evidence of guilt.
Some may well ask whether a person who fell asleep drunk in the middle of the road escapes punishment because of a glass of water. But this ruling does not take drunk driving lightly; it takes seriously the procedures the state must observe when it punishes a citizen. This column sets out the meaning of the ruling and what one should know at a drunk-driving checkpoint.
1. How Is a Breath Test Conducted?
A. Breath testing and blood sampling
Article 44(1) of the Road Traffic Act prohibits driving a motor vehicle or the like while under the influence of alcohol, and paragraph (4) sets the threshold at a blood alcohol concentration of 0.03% or more. Paragraph (2) provides that a police officer may test by breath whether a driver is under the influence and that the driver must comply, and paragraph (3) provides that a driver who disputes the result may be retested by blood sampling or similar methods with the driver's consent. Under paragraph (6), the methods and procedures of testing are delegated to the Enforcement Rules of the Road Traffic Act, an Ordinance of the Ministry of the Interior and Safety.
B. Why is water for rinsing the mouth necessary?
A breathalyzer measures the alcohol in air exhaled from the lungs and converts it into a blood concentration. If alcohol remaining in the mouth is measured along with it, the reading can come out higher than the actual level. That is why, according to the report, the Enforcement Rules of the Road Traffic Act require that the driver be given water to rinse out residual alcohol in the mouth before the test. The first and second instance courts regarded this as little more than an internal police guideline, and admitted the test result as evidence on the grounds that the effect of residual alcohol disappears once 20 minutes or more have passed since drinking, and that the driver suddenly bit the device and blew into it, leaving no time to offer water.
2. Why Did the Supreme Court Reject the Test Result?
A. The Enforcement Rules are not an 'internal guideline'
The Supreme Court held that the provision on offering rinsing water is not an internal standard for police work but a legally binding order concerning citizens' rights and duties. The police must provide the water and guide and encourage the driver to rinse the mouth thoroughly; while the driver is not required actually to rinse, the procedure cannot be skipped merely because the driver had been asleep. The Court also rejected the argument that the effect of residual alcohol disappears 20 minutes after drinking, reasoning that the relevant studies were conducted under limited conditions and it cannot be concluded that the risk of overestimation disappears in actual enforcement situations.
B. The exclusionary rule for illegally obtained evidence
Article 308-2 of the Criminal Procedure Act provides that evidence collected without following due process shall not be admissible. The courts have applied this principle consistently in drunk-driving cases as well. A leading example is the decision on blood drawn without a warrant.
Supreme Court Decision 2011Do15258, November 15, 2012If an investigative agency draws blood from a suspect without a warrant or an expert examination permit and without the suspect's consent, and does not obtain a warrant without delay afterward, the resulting blood alcohol analysis is evidence collected in violation of the warrant requirement and, in principle, cannot be used as evidence of guilt even if the defendant or defense counsel consents.
The same decision held that in urgent cases, such as a driver who lost consciousness after an accident and was taken to an emergency room, blood may be drawn without a warrant, but a seizure warrant must be obtained without delay afterward. The present ruling stands in the same line. However clear a reading may seem, if the process by which it was obtained departed from the procedure prescribed by law, the court cannot trust that reading.
C. The weight of the figure 0.081%
The procedure mattered all the more in this case because of the figure itself. Article 148-2(3) of the Road Traffic Act divides first offenses into brackets: a blood alcohol concentration of 0.03% or more but less than 0.08% is punishable by imprisonment of not more than one year or a fine not exceeding 5 million won, while 0.08% or more but less than 0.2% is punishable by imprisonment of not less than one year but not more than two years or a fine of not less than 5 million won but not more than 10 million won. Under paragraph (1) of the same Article, a person who violates the law again within ten years from the date a sentence of a fine or heavier became final faces a heavier penalty of imprisonment of not less than one year but not more than five years or a fine of not less than 5 million won but not more than 20 million won, even at 0.03% or more but less than 0.2%. In a structure where a difference of 0.001% changes the penalty bracket, the possibility that residual alcohol inflates the reading is by no means a small matter.
3. What to Know at a Drunk-Driving Checkpoint
A. If you are the driver being tested
You must not refuse the request for a test itself. Under Article 148-2(2)1 of the Road Traffic Act, a person who fails to comply with a test when there is considerable reason to believe that the person is under the influence of alcohol is punishable by imprisonment of not less than one year but not more than five years or a fine of not less than 5 million won but not more than 20 million won. So-called obstruction of a breath test, drinking more alcohol after driving in order to make testing difficult, is also prohibited by Article 44(5) and receives the same punishment. What you can do is comply with the test while checking the procedure. Remember whether you were given water to rinse your mouth before the test, and when you last drank and when you were tested, and if the reading seems wrong, you may request a retest by blood sampling on the spot.
B. If you have already been indicted
Start by checking the records of the testing process. Through the drunk-driver circumstance statement report, the test printout, the statements of the officers at the checkpoint, and video from the police box, you must examine whether water was offered, when the test was taken, and how it was conducted. If there is a procedural defect, the principle is to challenge admissibility from the first instance. However, the exclusion of the test result does not immediately mean acquittal. Being under the influence may be proven by other evidence such as witness statements, the circumstances of driving, and the amount and timing of drinking, and in this case, too, no acquittal has been finalized; the lower court will simply decide the case again. Separately from the criminal trial, administrative action on the driver's license proceeds on its own track, so both proceedings must be handled together.
4. Concluding Remarks
A glass of water seems trivial. But in a criminal trial, numbers become the basis for deciding a person's liberty, and confidence that those numbers are accurate arises only when the prescribed procedures have been followed. Drunk driving is a crime that must be punished strictly, and this ruling does not shake that principle. Rather, it confirms that punishment stands firm only when checkpoints follow procedure. For drivers, the surest defense is not to take the wheel after drinking, and for investigative agencies, not skipping basic procedures, especially at busy scenes, is the way to sustain a conviction.
(Shin Dong-woo, Managing Partner, DAEON Law Firm)
This column provides general legal information based on Korean statutes and court decisions as of 2026. 10. 27.. It is not legal advice on any individual case.
2026. 10. 27. · By Attorney Dongwoo Shin
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