Role of Expert Witnesses in DC DUI Cases

The role of expert witnesses in DC DUI cases can be important. When a prosecutor uses certain evidence against the person in a DUI case, their witness must be qualified as an expert. For example, there are three standardized field sobriety tests that police officers utilize during the DUI investigation. The horizontal gaze nystagmus (HGN) test requires specialized training to properly administer and interpret the test.  

The other two field sobriety tests involve the person standing on one foot and balancing while counting to 30 called the one-legged stand test and the walk-and-turn test where the person walks in a straight line heel-to-toe for nine steps. The person does not use their arms for balance, makes a specified turn, and then walks heel-to-toe in a straight line nine steps back. For more on these tests and the role of expert witnesses, contact a skilled drunk driving attorney immediately.

Field Sobriety Tests

The balancing and walking field sobriety tests do not require any specialized expert training or knowledge for the police officer to testify. However, the horizontal gaze nystagmus test requires specialized training. When the prosecutor has a police officer testify about the results of an HGN test, the police officer must be qualified as an expert. The officer must prove that they took the requisite training and have experience in administering and interpreting the HGN test. That is the most common expert testimony from the prosecutor’s side in a DUI case.

Chemical Test Results

The prosecutors may want to use chemical test results such as a breathalyzer, blood test, or urine test. When a police officer administers the breathalyzer test, the prosecutor must demonstrate through expert testimony that the police officer ran the test and is qualified to do so. When the police officer did not run a test such as a blood test or a urine test, the prosecutor must establish that the test was properly interpreted and analyzed.

Police officers do not do the analysis of a urine sample or blood sample. Those are sent to the lab. If the prosecutor wants to use the results from those tests, they must have an expert witness testify that the tests were properly administered and properly stored, analyzed, and completed before the evidence can be submitted and used against a person. The role of expert witnesses in DC DUI cases can be to analyze these tests.

Expert Witness for the Defense

In some DUI cases, it may be necessary to call an expert witness to refute the allegations that an individual was impaired by alcohol or drugs, whether that was through the physical manifestations of symptoms or signs of impairment or the alleged results of the chemical test. As an example, there are experts that can be called by the defense regarding the proper administration of field sobriety tests. When an officer did not properly administer those tests, it can be useful to have an expert called by the defense to highlight the issues. An attorney knows how to attack any deficiencies in the administration of the field sobriety test. Sometimes, it is helpful in a jury trial situation to have an expert witness speak about the issues.

Physical Characteristics

Other situations where an expert witness is useful or necessary relate to physical characteristics of a person. Some individuals suffer from disorders that affect the results of field sobriety tests and/or chemical tests, such as blood, breath or urine tests. The conditions can make it appear that an individual is under the influence of alcohol when in fact, they are not.

One example is when an individual has a history of head trauma or any other past traumatic injury. It can be useful and/or necessary to have an expert witness explain how those specific ailments or infirmities affect the person’s performance and the perception of the police officer viewing that performance on the field sobriety test. The expert witness in a DC DUI case can explain that the alleged signs and symptoms of impairment displayed on the field sobriety test do not necessarily mean the specific individual exhibited those clues because they were impaired by some substance. Rather, it can be due to ailments or disabilities they suffer from.

Chemical Tests

With chemical tests, there are ailments such as gastro-esophageal reflux disease (GERD). It is a digestive disorder that affects the lower esophageal sphincter (LES), the muscle between the esophagus and the stomach. The LES allows the contents of the stomach to come back up into the throat. It can cause heartburn or acid indigestion.

That can be extremely important information to have in a DUI case that involves a breathalyzer. Breathalyzers measure deep lung air and are set up to extrapolate a person’s blood alcohol content based on the breath that they are pushing into the machine. If there is any alcohol in the person’s throat or mouth at the time they perform the test; that can create a false high reading of the amount of alcohol in their bloodstream when they suffer from GERD or acute heartburn.

There are other conditions that can affect the accuracy of the blood alcohol score generated by the chemical test conducted by the police officer. They may require the role of expert witnesses in DC DUI cases to properly explain how the results of the police testing are not an accurate reading of the person’s impairment. The test results are affected by one of these other issues.