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Tips for Using an Expert Witness in Your DUI Case

by ptbarone on January 7, 2010

Witness Stand


After deciding which DUI lawyer to retain the next most important decision you will make is whether or not to use one or more expert witnesses.  Just like a DUI defense lawyer, if you pick the wrong expert you might just lose an otherwise winnable case. 

So, why are experts so important?  Expert witnesses can do one thing no other kind of witness can do – offer their opinion.  Here is what the Michigan rules of evidence say about experts in drunk driving cases: 

Rule 702 Testimony by Experts  

If the court determines that scientific, technical, or other specialized knowledge will assist the trier of fact to understand the evidence or to determine a fact in issue, a witness qualified as an expert by knowledge, skill, experience, training, or education may testify thereto in the form of an opinion or otherwise if (1) the testimony is based on sufficient facts or data, (2) the testimony is the product of reliable principles and methods, and (3) the witness has applied the principles and methods reliably to the facts of the case . 

Rule 703 Bases of Opinion Testimony by Experts  

The facts or data in the particular case upon which an expert bases an opinion or inference shall be in evidence. This rule does not restrict the discretion of the court to receive expert opinion testimony subject to the condition that the factual bases of the opinion be admitted in evidence hereafter. 

In a Michigan drunk driving case there are many different types of “specialized knowledge” that might help the judge or jury decide your case.  This includes information regarding the workings of the breath or blood test.  These kinds of experts are often called forensic scientists and have specialized knowledge about how these tests are done in a drunk driving case. 

Many of the DUI chemical test experts used by the Barone Defense Firm are former state employees that have switched to “the other side.”  These experts know exactly how the people that took your breath or blood sample are supposed to do their job, and often, how they fail to do it properly. 

Another are of specialized knowledge to explore with an expert in a drunk driving case would be the science of toxicology.  A toxicologist can help answer the question of how much alcohol is needed to create a breath or blood alcohol level, to help assist in or debunk “retrograde extrapolation,” and may also testify about how something like toluene or acetone can cause a false result in a breath test.  A toxicologist can also explain to the jury some of the problems that might occur with a blood test. 

Your lawyer may also want to hire an expert regarding the standardized field sobriety tests.  This type of expert is usually a current or former police officer who is trained as an NHTSA SFST instructor. 

There are many other experts that may be utilized depending on the specific facts of your case and any potential defenses.  Once you’ve made the decision with your DUI lawyer to hire an expert, make sure you are clear about the expert will do and how you will be billed. 

Also, make sure your DUI lawyer has explained to you how much the expert will charge, and when payment is expected or due.  It is a good idea to have the expert’s fee agreement in writing. 

Here is what one of the nation’s top DUI lawyers Bubba Head has to say about the issue: 


To learn more about experts, visit the James Publishing Blog and read: Selecting and Using Defense Experts in the DUI Trial


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