Home » Blog » DWI / DUI » Experts for DUI trials – Fairfax criminal lawyer comments

Experts for DUI trials – Fairfax criminal lawyer comments

Virginia DUI lawyer for Fairfax County, Arlington, Prince William & Beyond

Fairfax DUI lawyer top-rated by key attorney reviewers AVVO & Martindale-Hubbell

Call Us: 703-383-1100

Experts in Virginia DUI cases- Image of cocktail

Experts need to be considered for Virginia DUI trial testimony, says Fairfax criminal lawyer

Experts, also known as expert witnesses, often are ideal to bring to Virginia DUI trial dates. As a Fairfax criminal lawyer, I have used the services of expert witnesses in scores of cases, which enhances my ability to advise clients whether to obtain an expert and whom to select, to deal with the expert (particularly if I have dealt with that expert before), and to present the expert’s testimony in court.

Do I need experts for my Virginia DUI trial?

Experts are most often needed against Virginia DUI prosecutions when their testimony will help create reasonable doubt whether the defendant meets the 0.08 per se DWI definition, or else meets the 0.15 or over 0.20 threshold to qualify for enhanced mandatory minimum sentencing based on one’s blood alcohol content (BAC) reading through breath or blood testing. Expert testimony is also important for presenting a defense that the breath alcohol test is unreliable due to the defendant’s being a sufferer of acid reflux / Gastroesophageal reflux disease (GERD).

How do I know how strong are the arguments that I do not meet per se and mandatory minimum BAC thresholds for a possible conviction or enhanced sentencing?

To know how useful an expert or experts will be for one’s DUI trial, we start by looking at how strong are the defendant’s arguments to knock the claimed BAC reading below the 0.08 per se DWI threshold and the 0.15 and 0.20 mandatory minimum sentencing thresholds, respectively set at five days and ten days for a first time offense; and ten days and twenty days for a conviction for a second offense. For BAC readings under 0.15, Virginia DUI caselaw provides for the BAC at the time of driving to apply, whereby it is important to consider that one’s blood alcohol level at the time of driving may or may not have been lower than that level at the time of testing, in that first alcohol absorbs into one’s bloodstream (causing a rising BAC), then the alcohol level plateaus, and then the BAC starts to dissipate. When alcohol has been consumed close in time to the arrest time, that can increase the likelihood that the DUI suspect’s BAC is continuing to rise. At the same time, if the second of two post-arrest breath tests is lower than the first, that does not automatically mean that the BAC is automatically dissipating, when considering that the two breath samples are taken too close together to know that, and the air volume blown into the breathalyzer machine can affect the BAC content reading.

For BAC readings of 015 and over, Virginia DWI caselaw generally provides for applying the BAC at the time of breath testing or having one’s blood drawn. This is an artificial distinction from the caselaw that says to look at the BAC at the time of driving when the measured alcohol level is below 0.15, but is the governing caselaw.

For DUI cases involving breath testing, the defendant should very soon get three mouth temperature readings performed on sequential dates, because the Intox EC/IR II breath testing machine (which is the only breathalyzer authorized by the DFS) mis-assumes a mouth temperature of 34 degrees Celsius, when most people have mouth temperatures higher than that, does not check for actual mouth temperature, and does not adjust for mouth temperature. The right experts are equipped to testify about this mouth temperature phenomenon.

To know how strong will be the use of an expert or experts, it is necessary in breath testing cases to obtain testing and equipment performance data from the Virginia Department of Forensic Science (DFS) (both online and by mailed or faxed request to the DFS), and in blood cases to carefully review the certificate of analysis (which shows the DFS’s margin of uncertainty for testing) and to obtain a subpoena duces tecum / records subpoena for the DFS scientists’ notes, records and reports for testing the blood of the DUI defendant.

How do I know what type of experts to seek in my Virginia DUI case, and which ones should I choose?

Expert witnesses supplement, but never replace, having a quality Virginia DUI lawyer. When your DWI lawyer has worked with experts before, s/he will have a better idea of when an expert witness is advisable, which expert to choose, and how to deal with that expert. A forensic toxicologist often is the ideal expert to challenge Intox EC/IR II breathalyzer testing and blood testing (where the prosecutor is going to need his or her own expert to testify about his or her analysis of the blood). Ideally that expert will have been trained on such testing by or through the manufacturer of the applicable breathalyzer testing machine, which can be a challenge if the manufacturer resists defense expert witnesses being trained on such equipment. I repeatedly have used the services of a forensic toxicologist who has been trained on this breathalyzer machine through the manufacturer. For dealing with expert testimony for an acid reflux / GERD defense, see my article here.

This is the first of a two-part article. The second part is here. 

Fairfax DUI lawyer Jonathan Katz has successfully defended hundreds of people charged with DWI. Call 703-383-1100 for a free in-person confidential consultation with Jon Katz about your court-pending DUI or criminal case.