Expert Testimony in DUI Cases

Drunk Driving Defense Lawyer for Phoenix Area Residents

Expert testimony may be necessary to a strong defense of your DUI case. A credible and knowledgeable expert who presents well on the stand can make a difference in whether charges for drunk driving lead to a conviction. If you have questions about expert testimony in your case, James E. Novak may be able to help. Mr. Novak is an experienced Phoenix DUI attorney who can use the insights and knowledge he developed during his time as a prosecutor when building your defense.

Expert Testimony

Arizona Rule of Evidence 702 governs expert testimony. An expert is allowed to testify when her technical, scientific, or other specialized knowledge would help the fact finder to understand the evidence or decide an issue. Additionally, the expert’s testimony must be based on sufficient data or facts, and must be the result of applying reliable methods and principles to the case in a reliable manner.

Expert testimony may be needed in DUI cases to prove whether field sobriety tests, blood tests, or breath tests were legitimate. If the results of a field sobriety test work against you, if applicable it might be appropriate to retain a medical expert witness who can explain that your poor balance (or another characteristic that suggested drunkenness to an officer) was because of a preexisting condition. For example, if you have vertigo, it may be possible to show through expert testimony that your lack of balance was the result of vertigo, not intoxication.

Alternatively, it may be possible to put forward an expert who can show that there is a lack of scientific reliability in field sobriety tests. For instance, your expert may testify to the fact that your field sobriety test was either not reliable in general, or that was not reliable in light of the way it was performed.

It may also be possible to challenge a breath alcohol test. Breathalyzers can malfunction or be defective. A scientist or former law enforcement officer with the appropriate education may be able to testify that a breath test malfunctioned in your DUI case.

Similarly, it might be possible to challenge blood or urine test evidence with expert testimony. For example, if the laboratory maintained poor quality assurance protocols, it may be possible to show that their protocols make it impossible to show that your blood alcohol concentration was as high as it was claimed to be by presenting the testimony of forensic lab expert witnesses. Sometimes it’s possible to present a medical expert to explain that a preexisting condition affected your blood alcohol test results as well.

If you’re facing a drugged driving charge, your DUI attorney may be able to help you present an expert to counter the prosecution’s claim that you were impaired either by illegal drugs or pharmaceuticals. Sometimes, when the prescription medication is one like Ambien or Klonopin, a pharmacologist may be able to testify that you were taking the medication within a prescribed therapeutic dose.

Limitations on Expert Testimony

Lower court judges possess the discretion to restrict expert testimony in DUI cases and other matters if the testimony is irrelevant or unreliable. When determining whether an expert witness is reliable, the factors the court should consider are: (1) whether the evidence at issue was subject to scientific testimony and what methodology was used, (2) whether the evidence was reviewed by a scientific publication or peers, (3) what the known potential error rate is, and (4) whether the evidence is generally accepted in the scientific community. Though judges have this latitude, the jury will decide how credible a particular expert is or how much weight to give his or her opinion.

Phoenix Attorney for DUI Charges

The penalties for a DUI can sometimes be significant. Knowledgeable, seasoned counsel can defend you and help you determine a strong defense strategy, which may include retaining a credible expert to testify. If you’re concerned about expert testimony in a DUI case in Phoenix, you can discuss your circumstances with criminal defense lawyer James Novak. Mr. Novak defends those who are being prosecuted for drunk or drugged driving in the Phoenix area, including in Mesa, Gilbert, Chandler, and throughout Maricopa County. Call him at (480) 413-1499 or contact us via our online form.

Client Reviews
I was facing criminal charges with three priors in my history. Mr Novak was very helpful and got me a lighter sentence than I probably deserved. He is a great attorney and I would highly recommend him. A. T.
James worked tirelessly behind the scenes with the prosecution, to decrease my son’s charges to a more reasonable penalty. I could not have asked for a better, more professional attorney. He treated my son with the utmost respect and walked him through every step of a very difficult situation. S. G.
Attorney Novak did an outstanding job defending my son. Due to his extensive professional background within the court system, he was successfully able to defend my son during a very difficult time for my family. I highly recommend Attorney James Novak for your legal needs. T. G.