Testimony in New Jersey DWI Cases: Expert Witnesses

Prosecutors who handle New Jersey driving while intoxicated (DWI) cases must prove that a defendant is guilty beyond a reasonable doubt. They present evidence in order to establish that a defendant was under the influence of alcohol or drugs. In order to counter this evidence, a defendant may need to produce an expert witness. A compelling report from an expert could even convince a prosecutor to drop a DWI charge. If not, the expert can testify at trial about their findings. An experienced DWI defense lawyer can identify where expert testimony would be most helpful and can find qualified experts for your case.

What Is an Expert Witness?

Rule 702 of the New Jersey Rules of Evidence (NJRE) defines an expert witness as someone who has particular “scientific, technical, or other specialized knowledge,” which they have attained through “knowledge, skill, experience, training, or education.” This definition has three important components:
1. The subject must be beyond many or most people’s understanding.
2. The witness’ field of expertise must be established enough to provide reliability.
3. The witness must demonstrate that they have achieved expertise in the field.
Unlike other witnesses, expert witnesses may testify about their opinions, as long as those opinions are based on their expert knowledge and can help a judge understand a DWI case.

A police officer with training in the use of Alcotest devices, for example, may testify about the condition and reliability of the machine used to test samples of a defendant’s breath. A drug recognition expert (DRE) could testify about their conclusion, based on training and experience, that a defendant was under the influence of a particular drug or type of drug.

A defendant can retain the services of a toxicologist, a physician, or someone with experience in DWI cases or auto accidents. Depending on their area of expertise, a defense expert could:
– Challenge the calibration or maintenance of an Alcotest device;
– Offer alternative explanations for behavior that led a DRE to suspect impairment by drugs;
– Challenge the results of chemical tests on blood or urine samples;
– Question whether a police officer administered field sobriety tests correctly; or
– Reconstruct an accident scene to show that alcohol was not a factor.

Qualifying an Expert Witness

In order to qualify as an expert, a defendant must show that their witness and the witness’ area of knowledge meet the requirements of Rule 702. The U.S. Supreme Court adopted a standard for qualifying expert witnesses in a 1993 decision, Daubert v. Merrell Dow Pharmaceuticals. New Jersey has adopted the Daubert standard in many kinds of cases. In criminal and motor vehicle cases, however, this state still uses the Frye standard, named for a 1923 federal appellate court decision.

Under the Frye standard, a court must find that an expert witness’ method of reaching their conclusions has been generally accepted by other experts in that particular field. The New Jersey Supreme Court declined to drop the Frye standard in favor of Daubert in a 2018 decision. It noted this again in a DWI decision later that year.

If you are facing alleged DWI charges, you need an experienced and knowledgeable advocate who can fight for your rights both in and out of court. DWI attorney Evan Levow has dedicated 100% of his law practice to defending people charged in New Jersey municipal courts. Please contact us today online or at (877) 593-1717 to schedule a free and confidential consultation to see how we can help you.

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