Police in New Jersey often ask individuals suspected of driving while intoxicated (DWI) to perform field sobriety tests (FSTs), which allow officers to look for supposed signs of intoxication. Of the three standard FSTs used by New Jersey law enforcement, two are based entirely on the ability to maintain balance. Various injuries and medical conditions can also affect performance on these tests. It is possible for a defendant charged with DWI to produce evidence about an injury or illness to challenge an officer’s testimony about FST performance, although this is usually not the only evidence of intoxication the state will offer. In early 2019, the New Jersey Superior Court, Appellate Division ruled on a New Jersey DWI case with this kind of challenge.
The DWI statute requires proof that a defendant was either “under the influence” of alcohol or drugs or had a blood alcohol concentration (BAC) of 0.8 percent or higher. Prosecutors often introduce evidence of both, for good measure. If a person refuses or is unable to submit a breath sample for BAC testing, prosecutors must rely on evidence that a person was “under the influence.” A 1975 decision by the New Jersey Supreme Court established that this term means “a substantial deterioration or diminution of the mental faculties or physical capabilities of a person” caused by alcohol or another drug.
In 2006, the state supreme court ruled that expert testimony, such as by a physician or other medical professional, is not necessary to demonstrate the “influence” of alcohol or drugs. Testimony from police officers who witnessed a defendant’s behavior and appearance can, by itself, sustain a conviction for DWI. This might include testimony about slurred speech or bloodshot eyes, the odor of alcohol, or swaying or stumbling during the FSTs. A defendant with a health condition that could impact their FST performance, on the other hand, usually must present expert testimony.