Three Types of Expert Witnesses That Can Be Useful in a DWI Case

Posted by Doug Murphy | Jun 02, 2020 | 0 Comments

The state utilities police officers that they proffer as expert witness, when in fact they are just police officers with police training.  That training does not in and of itself make them expert witnesses.  The manner in which they testify in court and the verbiage they are trained to use makes them sound like they have more expertise than they actually have. Board certified DWI lawyers know how to easily challenge and defeat these state "expert witnesses".   Use of legitimate expert witnesses can also be helpful to the defense in certain Texas driving while intoxicated trials.  In fact, there are some circumstances where the right expert witness could be the difference between an acquittal and a conviction.

The use of these experts should not be taken lightly.  In many cases, calling these witnesses can be costly. What's more, not all expert witnesses will be useful in every DWI trial. To determine if expert testimony is right for your defense, speak with a Houston Board Certified DWI defense attorney right away. Below, we discuss three of the most common types of expert witnesses used during DWI trials.

Forensic Toxicology Experts

Forensic toxicology often plays a major part in DWI cases given the common use of blood alcohol concentration (BAC) tests. The results of these tests can be damaging to your case if not properly explained to demonstrate what weight, if any, this evidence should be given. There are instances where an unbiased expert forensic toxicologist could show how the results of your blood or breath test are inaccurate. This can occur in a number of forensically unacceptable ways. For example, the blood sample tested was compromised, or the testing methodology was not followed, or there was break in the chain of custody.  It could be the drug metabolites tested in the blood sample are actually inactive metabolites that do not demonstrate drug impairment.  In breath testing here are certain foreign substances like sugar-free gum, kombucha, and honey buns that can cause a false positive test. A forensic toxicologist could help explain how these circumstances created a bad test result or a false positive in your case.

In rare cases, there are also other medical conditions that result in your body naturally occurring alcohol in your gut even when you do not consume alcohol.  In these cases, expert testimony could be vital.

Accident Reconstruction Experts

While accident reconstruction experts are more likely to be involved in a civil lawsuit, there are circumstances where they can play an important role in a criminal case. When a DWI case involves an accident with serious bodily injury or death, whether or not the criminal defendant caused the crash could be an important factor. The state might argue that an accident occurred as the result of a driver's intoxicated state. However, testimony from an expert that another driver or even a mechanical defect was to blame could limit the prosecution's evidence of intoxication.

Field Sobriety Test Experts

It is vital for law enforcement to perform each step of standardized field sobriety tests correctly. After all, these exercises are admittedly far less accurate if the officer fails to carefully follow each step of the process.

In many DWI cases, the officer's dash camera will record a person suspected of DWI performing these field sobriety tests. An expert in training or performing these tests could highlight to a jury through the use of this video how the arresting officer failed to properly conduct the tests.  An expert could go further, helping the jury understand why failing to properly administer field sobriety tests makes their results useless for detecting intoxication.

Let a Board Certified DWI Expert in Houston Advise You

The decision to rely on an expert witness should not be made alone. Just like every aspect of your defense, it is crucial that you seek experienced legal counsel. That said, not just any attorney will do. To maximize your chances of a favorable outcome, contact a Board Certified expert in DWI defense as soon as possible.

About the Author

Doug Murphy

Doug Murphy is one of only two Texas lawyers Board Certified in Criminal Law by the Texas Board of Legal Specialization, and also in DWI Defense by the National College for DUI Defense, accredited by the American Bar Association and the Texas Board of Legal Specialization.


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