A breath alcohol test conducted without giving a suspected drunk driver water to rinse their mouth cannot be used as evidence of guilt, South Korea's Supreme Court has ruled. The court said police failure to follow the procedure — designed to account for the possibility that alcohol left in the mouth skews readings — means the test result cannot be admitted as evidence.
According to legal sources on the 25th, the Supreme Court's First Division, with Justice Chun Dae-yeop as the presiding judge, overturned a lower court ruling that had sentenced a person surnamed Kim to one year in prison, suspended for two years, on charges of violating the Road Traffic Act through drunk driving. The case was sent back to the Daejeon District Court.
The incident occurred around 8 p.m. in December 2023. Police responded to a report of a person asleep in a vehicle with the engine running in the middle of a road and arrested Kim at the scene. Officers then moved Kim to a local police substation and laid Kim on a bench.
An officer approached Kim with water in a paper cup but turned away without waking Kim. Officers then repeatedly held a breath analyzer near the mouth of the sleeping Kim in an attempt to take a reading. Around 8:50 p.m., Kim suddenly sat up and blew into the device, registering a blood alcohol level of 0.081%.
Prosecutors indicted Kim on a charge of driving with a blood alcohol level of at least 0.03% but below 0.08% — a lower range than the recorded reading. Kim had also received a summary order with a fine of 1 million won in 2019 on a drunk driving charge.
At trial, Kim argued that police had not provided water to rinse out the mouth before the test. Because alcohol remaining in the mouth could have pushed the reading above the actual blood alcohol level, Kim argued, there was no basis to conclude the level had been at or above 0.03% while driving.
The trial court and the appeals court both rejected that argument, each imposing a one-year prison term suspended for two years.
The appeals court found that because Kim had been lying on a sofa and abruptly took the analyzer into the mouth and exhaled, officers had little opportunity to offer water beforehand. Taking the circumstances as a whole, it concluded that Kim's blood alcohol level could be recognized as having been at or above 0.03% and that the reading was admissible as evidence of guilt.
The Supreme Court took a different view, holding that a breath test result obtained without actually providing rinsing water cannot be used as evidence.
The court said officers conducted the breath test without giving Kim rinsing water, thereby undermining the substance of the rinsing-water procedure set out in the enforcement rules.
It found in particular that officers had ample opportunity to wake Kim, who was asleep on the substation bench, provide water and instruct or encourage Kim to rinse out the mouth thoroughly. There were no unavoidable circumstances preventing them from doing so, the court said, yet they repeatedly attempted only to take a reading.
The Supreme Court also noted that the procedure had been formally in force nationwide for more than six years under the National Police Agency's internal traffic enforcement guidelines, and that a related provision had been added to the enforcement rules and in effect for nearly six months by the time of the test.
The officers, the court said, would therefore already have known that rinsing water must be provided to a driver before a breath alcohol test and that the procedure is of considerable importance.