A Glass of Water Upends a Drunk Driving Verdict: Why the Supreme Court Overturned the Ruling [Soup]

In December 2023, a freight truck was found parked in the middle of a road in Sejong with its engine running. The driver, surnamed Kim, was asleep. Police conducted a breathalyzer test, and the result showed a blood alcohol concentration of 0.081 percent, a level warranting the revocation of a driver's license. The first and second instances found Kim guilty. However, this ruling was overturned by the Supreme Court—all because of a glass of water.

Kim had a prior record of receiving a fine for drunk driving back in 2019. Prosecutors applied charges of repeat drunk driving, and Kim was found guilty in both the first and second trials. Yet, the Supreme Court delivered an unexpected ruling at the final stage, breaking the lower court's sentence of one year in prison suspended for two years and sending the case back to the Daejeon District Court.

01. Overturned by a Glass of Water

What was the reason behind the sudden reversal of the verdict? The issue was that the police did not provide Kim with water to rinse his mouth before the breathalyzer test. Back in 2017, the Korean National Police Agency revised its traffic enforcement guidelines to mandate providing drivers with 200 milliliters of water to rinse their mouths prior to sobriety tests. Starting in July 2023, this procedure was also explicitly stated in the Enforcement Rule of the Road Traffic Act, giving it legal binding force.

However, this procedure was not carried out at the time of Kim's breathalyzer test. Kim argued that because the police did not provide water to rinse his mouth, his blood alcohol concentration at the time of testing may have been measured higher than the actual level. While Kim's argument was rejected in the first and second trials, leading to guilty verdicts, it became the decisive factor in overturning the judgment at the Supreme Court.

At the time, police approached the sleeping Kim to give him water but turned back, and Kim subsequently complied with the test suddenly without being given an opportunity to rinse his mouth. The Supreme Court ruled that the procedures stipulated by law cannot be omitted simply because Kim was asleep. It stated that breathalyzer test results obtained without following the water-provision procedure cannot, in principle, be used as evidence of guilt.

02. Why 'Mouth Rinsing' Became the Core Issue

The core issue in the contrasting rulings was the residual alcohol remaining in Kim's mouth. The first trial concluded that "because the test was conducted more than 20 minutes after Kim had consumed alcohol, residual alcohol in the mouth was unlikely to have affected the measurement." However, the Supreme Court judged that "since variables such as hiccups or burps can occur at actual drunk driving crackdown sites, the possibility that the breathalyzer reading came out higher than the actual level cannot be ruled out simply because 20 minutes have passed."

The Supreme Court did not acknowledge that Kim's actual blood alcohol level was lower, and it remains possible that the actual measurement result was accurate. However, it maintained that whether a result obtained without going through legally prescribed procedures can be used as evidence of guilt is a separate matter.

Then, how much does alcohol remaining in the mouth actually affect breathalyzer test results? A study conducted in the United States in 1978 showed that when individuals did not actually drink alcohol but only brought alcoholic beverages into contact with their mouths before taking a breath test, it took 10 to 19 minutes for the effect of the residual alcohol in the mouth to dissipate. Furthermore, rinsing the mouth with warm water significantly shortened that time. This indicates that residual alcohol in the mouth can affect measurement values, and rinsing the mouth with water can mitigate that impact.

03. Fifteen Minutes That Reversed the Verdict

Police in Michigan, USA, specify in their guidelines that drivers must be observed for at least 15 minutes before a breathalyzer test. This rule ensures verification that no factors capable of affecting the readings, such as smoking or regurgitation, have occurred prior to testing. Failure to properly follow this procedure can result in test results not being recognized as evidence.

In fact, in 1995 in Michigan, USA, a driver who had admitted to drunk driving raised an issue that police had not sufficiently observed him during the breath testing process, and the court overturned the guilty verdict. The reason was that the failure to observe the driver for at least 15 minutes prior to the breathalyzer test made it difficult to trust the accuracy of the measurement results. A similar ruling occurred in 2021 where test results were excluded from evidence due to flaws in the testing procedure.

Following this Supreme Court ruling, forecasts suggest that legal disputes surrounding testing procedures may continue in domestic drunk driving trials going forward. In particular, experts note that as measurement readings get closer to punishment thresholds, even small amounts of residual alcohol can affect the outcome, making footage confirming conditions at the time of enforcement—such as police body cameras or dashcams—potentially even more crucial.

Last year, a total of 121 people lost their lives to drunk driving traffic accidents. Given that drunk driving is a dangerous crime capable of taking the lives of others, there is likely no disagreement that it must be strictly punished. However, if the evidence supporting the punishment did not go through accurate procedures, can we trust that punishment? This ruling, divided by a glass of water, prompts us to rethink the importance of the process used to secure evidence, alongside strict punishment for drunk driving.


Deep Dive Q&A
Q1. What is the legal basis for providing drivers with 'water to rinse the mouth' before a breathalyzer test, and what legal doctrine did the Supreme Court apply when this was not followed?

A1. It is a due process procedure specified in the Enforcement Rule of the Road Traffic Act, which mandates providing 200 ml of water to rinse the mouth before breath testing to prevent test results from being distorted by residual alcohol or refluxed substances remaining in the mouth. Citing the 'due process principle' under the Constitution and the Criminal Procedure Act, the Supreme Court reversed and remanded the case by applying the 'exclusionary rule for illegally obtained evidence,' which dictates that breathalyzer test results collected without complying with procedures prescribed by law cannot, in principle, be used as evidence (evidentiary capability) to prove guilt.

Q2. What are the specific changes and impacts this Supreme Court ruling will bring to future drunk driving crackdowns and related trial scenes?

A2. Police officers' duty to comply with investigative manuals at sobriety checkpoint sites will be significantly strengthened. Lawsuits raised by suspects over procedural flaws are expected to surge, particularly for those whose crackdown readings are close to punishment thresholds. Consequently, investigative agencies are projected to place even greater importance on police body camera recordings and on-site evidence collection to verify whether water was provided during enforcement, adequate observation time was secured, and suspect statements were properly recorded.
※ Please note: This article was translated by AI and may contain errors.