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Identifying The Expert Appropriate For Your Georgia DUI Case

The following is an except from a paper I presented at the “Georgia Defense of Drinking Drivers Institute” seminar on December 1, 2011.


Sometimes we have to make a decision about what portion of the case in which to employ an expert. In the vast majority of cases, the decision as to what portion of the case that you will use an expert witness for is pretty clear: you want to use an expert witness to attack the chemical test.  If given the choice between retaining an expert that will address simply the chemical test or an expert who will address field sobriety evaluations and non-field sobriety observations of our client, we would generally rather have an expert witness that will address the reliability and accuracy of the chemical test.  Because the most difficult piece of evidence to overcome in a standard alcohol case involving a breath or blood test is the numerical value presented by the state-administered chemical test, it only stands to reason that we want an expert to address that part of the case.

Include your client in the decision as to which expert and what type of expert to retain.  We do not want to be in a position after the case is completed where the client asks why a particular expert was used, or why they were not included in the decision to retain the expert.  Remember, this is the client’s case, their money, and their life that will be affected by this case.

Generally, experts are relied upon in the following “categories” of cases:

  • The “Double-Refusal” Case – (Field Sobriety Expert)

In those cases in which our client declines to submit to both field sobriety testing and the state-administered chemical test, typically, no expert is used.  However, an expert may be beneficial in some of these cases in order to correct overstatements by the officer.  Simply having a pre-trial hearings can be extremely useful in limiting the need to expend funds for an expert.  If you can use the pre-trial hearing to limit the officer’s testimony relating to the manifestations that allegedly support his conclusion of impairment, you may render the expenditure of funds on an expert unnecessary.

  • Submission to Field Sobriety Testing and Refusal of the State-Administered Chemical Test – (Field Sobriety Expert, Medical Expert, Accident Re-constructionist)

In those cases in which our client submits to field sobriety testing and declines the state-administered chemical test, a field sobriety expert, medical expert, or even an accident re-constructionist can be very useful.  Our ability to analyze the officer’s performance of field sobriety testing on the video and testimony in pre-trial hearings is crucial to limiting the expenses that our clients incur in these types of cases.

  • Submission to Field Sobriety Testing and the State-Administered Chemical Test – (Field Sobriety Expert, Chemical Test Expert, Medical Expert, and Accident Re-constructionist)

In those cases in which our client submits to field sobriety testing and the state-administered chemical test, it is possible to have multiple experts involved in the case.  Obviously, there are certain strategic and financial limitations to that strategy, but it is possible.

There are different types of experts.  Like every profession, there are some experts that limit the scope of their work to a very defined subject matter, and there are some experts that comfortably speak to an array of different disciplines based upon their training and experience.  Consider those experts that testify with regard to multiple different disciplines as hybrid experts, and there are cases in which they are highly effective.  Alternatively, there are cases which clearly require the expertise of a specialist.

Hybrid experts usually testify with regard to field sobriety tests and the chemical test (particularly the breath test).  In many cases involving field sobriety tests, we rely upon former police officers who have extensive training in standardized field sobriety testing and have made hundreds of DUI arrests trainings.  Most former officers also underwent training in forensic breath alcohol testing.  Their breath alcohol training may have included training with regard to quarterly inspections and possibly operator and maintenance training with CMI.  This type of expert can help you with field sobriety testing and, in the right case, assist in attacking the breath test.

We must be careful about our use of hybrid experts.  Assume that we have a very good issue to attack with regard to the State’s breath test, but we have an officer who administered the standardized field sobriety tests in accordance with NHTSA protocol.

The hybrid expert, who has exceptional training in field sobriety performance, will be subject to cross-examination on the officer’s performance in the case.  We have recognize this possibility and be prepared for our own expert to be used to corroborate the officer’s field sobriety testing testimony.

In contrast to hybrid experts, specialists are very restrictive in regard to the scope of their testimony.  Typically, when we mount a defense to a chemical test that is based upon a very technical issue, such as failure of the slope detector in the Intoxilyzer or co-elution of peaks in a blood test chromatogram, we need a very technically proficient and specialized expert.  A specialist is significant for this type of defense because (1) the qualifications of a specialist are needed in order for the opinion based upon these issues to be credible and (2) most likely only a specialist can provide this type of testimony.

It is important that we recognize this limitations of the specialist expert’s testimony, protect it, and respect it during the course of our direct examination.  The specialist’s limited testimony is a tremendous value to us in the trial.  The specialist is not “over selling” his opinion, so do not seek to unnecessarily his testimony on direct examination.  With the specialist’s opinion before the jury, the State is unable to argue to the jury that this expert “has an explanation for everything” because their opinion is limited to a very specific issue.

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The Sessions Law Firm, LLC

3155 Roswell Rd., Ste. 220
Phone: 470-225-7710

About the Author

Ben Sessions, Attorney at Sessions Law Group
Ben Sessions

I work to provide exceptional service, attention, and results to each of my clients. Most of clients come to me because they are in a completely overwhelming situation. They need someone that will do more than address their legal problems.


Hiring a lawyer is about more than getting a great result in your case. We understand that for many of our clients, the event that led them to call us causes them tremendous stress and anxiety. We will help you understand the process and how we can help. When you hire The Sessions Law Firm for your case, you will have a lawyer that is willing to take the time to help you and committed to delivering the best results possible.