New Jersey law allows prosecutors to offer evidence of driving while intoxicated (DWI) in two ways. One way relies on evidence like testimony by police officers about outward signs of intoxication, including appearance and behavior. The second method involves evidence that a defendant’s blood alcohol content (BAC) was above a certain level. This is often known as “per se” DWI because the BAC evidence creates a presumption that the defendant was impaired by alcohol. A DWI defense strategy should take both methods of proving DWI into consideration. Defending against a per se DWI charge in New Jersey often involves challenging police equipment more than police witnesses. The Appellate Division recently considered an appeal of a per se DWI conviction in State v. Page.
The DWI statute defines the offense as driving either “while under the the influence” of alcohol or drugs or with a BAC of at least 0.08 percent. The latter definition constitutes per se DWI. It does not necessarily require any evidence other than the defendant’s actual or imminent operation of a motor vehicle and the defendant’s BAC at or near that time. It is possible to obtain an acquittal or dismissal in a DWI case even with evidence of a BAC over 0.08 percent. It is also possible, however, for the state to obtain a conviction without BAC evidence or with a BAC of less than 0.08 percent.
New Jersey courts have established a variety of procedures and protocols that police must follow in an effort to ensure the accuracy of BAC test results. Police in this state commonly use a device known as the Alcotest to measure BAC. The defendant must provide a breath sample by blowing into a tube. The device then measures the alcohol content of the sample. The Alcotest requires regular maintenance and careful calibration, and it can produce inaccurate results without either of these. A 2008 decision by the New Jersey Supreme Court, State v. Chun, establishes maintenance and record-keeping protocols that police must follow for Alcotest results to be admissible in court. It also requires police to observe a DWI suspect for 20 minutes before administering the test.