Understanding the Role of an Expert Witness in a DUI Case in Kansas City, MO
If you’re facing a DUI case in Kansas City, MO, you need to know the role of an expert witness. Contact the Missouri DWI & Criminal Law Center today for assistance.
Kimberly J. Benjamin, Founder & Managing Attorney
May 15. 2023.
DUI Expert Witness
Expert witness testimonies carry a lot of weight and are essential in DUI cases. This is because an expert witness has the technical knowledge, education, and training to collect, test and evaluate evidence.
Their specialized skills allow them to better explain certain facts about a Driving Under the Influence (DUI) or Driving While Intoxicated (DWI) case that may not be seen from simple observation.
Expert witnesses may do the following in your DUI case:
Issue a medical, scientific, or environmental opinion that supports the defense in your case.
Provide expert reports and evidence to educate and inform the DMV officer on specific facts of your case.
Issue an opinion that strengthens the prosecutor’s case against you.
Testify at the trial or administrative hearing to convince the jury why the evidence is faulty.
Issue an argument that convinces the prosecution to drop the charges or reduce them to a lesser offense.
Identify if the documents or results presented to the court are false.
Why Expert Witness Testimony is Beneficial in a Kansas City DUI Case
Expert witnesses assist the jury in understanding chemical test results, breath test results, blood tests, and Standardized Field Sobriety Tests (SFSTs). They question the validity of test results and explain how external factors may impact these results.
Some of the tests the arresting officer uses after making a stop require specialized training to administer and interpret them correctly.
For instance, FSTs and breath tests may be affected by several factors that may render the results inaccurate, including an incorrect testing procedure or a faulty machine.
Experts That Can Be Helpful in a DUI Case
Expert witnesses are not required in every DUI case. However, some common types of experts used in DUI cases include:
Field sobriety expert
Accident reconstruction expert
Police Practices and Procedures Expert Witness
A law enforcement officer must follow detailed procedures when administering SFSTs during a DUI investigation. Failing to do so may result in inaccurate test results and will question whether the police officer had probable cause before arresting you.
Police procedures expert witnesses testify on the tactics and procedures a law enforcement officer uses during a stop, arrest, or when conducting testing. If there was an error in administering the breathalyzer test, their expert testimony on the error could render the test results inadmissible.
Police officers may use three SFSTs during a DUI investigation, including the Walk and Turn, the One-Leg Stand, and the Horizontal Gaze Nystagmus test (HGN).
The officer uses them to observe the driver’s balance, dexterity, coordination, ability to focus, and physical abilities.
The balancing and walking SFTs do not require expert training or knowledge for the officer to testify. However, the HGN test requires specialized training.
A police officer must be admitted as an expert witness before he can testify about the results of the HGN test. The police officer must be qualified as an expert.
The officer must show that they completed the requisite training and have experience administering and interpreting the HGN test.
The Role of an Expert Witness at Trial
Under Missouri Law, an individual charged with DUI may be required to appear before a judge and jury in a criminal court.
Expert witnesses are called to take the stand after a presentation of direct evidence testimony and specific foundational evidence.
They must have the required qualification and experience in the eyes of the court before they will be allowed to give an opinion on the evidence presented by the defense or prosecution.
Generally, like in a DWI case, expert witnesses provide expert opinions on the tests and procedures a law enforcement officer performs during a DUI investigation.
For instance, a forensic toxicologist who is an expert witness in a DUI case will provide information on the tests they carried out on the blood sample as well as their professional opinion on the findings, including:
Whether the blood test was administered correctly
Whether the blood test was properly stored
Whether the test was properly analyzed and interpreted
Expert Witnesses for the Defense
The defense may call an expert witness to refute the allegations that an individual committed DUI. In addition, the expert witness can challenge the justification of the police officer for the arrest.
For example, police officers often administer chemical tests to measure the blood alcohol concentration (BAC) in your breath, blood, urine, or saliva.
With chemical tests, there are ailments such as gastroesophageal reflux disease (GERD), which may allow alcohol consumed by a person earlier to come back up into the throat, causing heartburn.
If a breathalyzer test is done on a driver with such a condition, based on their breath at the time, the test may generate a false high reading of alcohol in their bloodstream.
The defense can call a medical expert to testify of the driver’s condition and how it could adversely affect the breath test results.
Further, the prosecution may only use urine samples sent to a lab if an expert testifies that they were adequately administered, stored, and analyzed.
The defense can show that the expert lacked the required qualifications or that a critical foundation for admissibility is missing.
A DUI attorney knows how to attack deficiencies in the administration of SFSTs and can defend against drugged driving by having an expert witness speak about specific issues, such as a field sobriety test at trial.
Importance of Having a Defense Attorney Who Knows Good Experts
An experienced DUI lawyer at the Missouri DWI & Criminal Law Center knows which experts can be relied upon and are given proper respect and consideration by the fact-finder, the courts, and the juries.
We can also examine each government’s proposed expert witness’s training, experience, and alleged expertise to determine whether they qualify.
Suppose you have an attorney who is inexperienced in expert witness testimony. In that case, they may be unable to lay a proper evidentiary foundation to allow your expert to testify to the full extent of their knowledge.
In addition, if you have an attorney who needs to gain knowledge of relevant experts in the field applicable to your case, you may be unable to locate a strong expert witness to come in on your behalf.
What makes us different than all other law firms is that our founder is on the faculty and we are each trained at the Gerry Spence Trial Lawyers College, the premier trial lawyer training program in the USA. Every Kansas City criminal defense attorney at our law firm trained with the best, so our clients can relax knowing their criminal defense lawyer is ready for anything.
If you or your loved one requires an expert witness to testify on your behalf to prevent a driver’s license suspension or criminal conviction, call today: 816-281-5306
If you have been drinking, use our "Blood Alcohol Content (BAC) Calculator"to estimate your Blood Alcohol Content (BAC) before you drive, but please keep in mind that the information it provides is just an estimate and may not be inaccurate.
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