As a New Jersey drunk driving defense attorney, I and my fellow lawyers must know all the details of DWI law and the processes that law enforcement agencies use to determine legal intoxication due to alcohol consumption. Part of this knowledge is how a breath testing machine, such as the Alcotest device, is used and procedures required by law that make any reading valid and useful in a court of law.
In New Jersey, the law states that for a breathalyzer machine to yield readings that can be used with confidence, the operator must ensure that at least 20 minutes have elapsed since the drunk driving suspect’s last ingestion of alcohol before administering the test. The reason for this is to avoid any possible presence of what is termed “mouth alcohol.” If this observation period is not followed, there is a chance that the machine can give a falsely high reading, as per State v. Downie, 117 N.J. 450, 455 (1990).
Although the term “ingestion,” is used here, the main purpose of the 20-minute time interval is so the breathalyzer operator can be assured that there is no alcohol present in the suspect’s mouth at the time of testing. As stated previously, any residual alcohol in the person’s mouth could cause an inaccurate measure of breath alcohol, which would invalidate the reading and call into question the procedures used by police.
The Alcotest machine (model 7110 MKIII-C) is equipped with a “slope detector” that supposedly is capable of detecting the presence of mouth alcohol, which could affect a breath test result. Regardless, the New Jersey Supreme Court in State v. Chun, 194 N.J. 54, cert. denied 129 S.Ct. 158, 172 L.Ed.2d 41 (2008) held that an operator must wait 20 minutes before collecting a sample to avoid overestimated readings due to residual effects of mouth alcohol.
The court’s decision included an additional requirement, such that the operator must observe the test subject for the required 20 minutes to ensure that no alcohol has entered the person’s mouth while awaiting the start of the test sequence. Additionally, if the suspect swallows anything, or regurgitates, or if the operator notices chewing gum or tobacco in the person’s mouth, the operator is required to begin counting the 20-minute period anew.