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Calling Expert Defense Witnesses In A DUI Case

Calling Expert Defense Witnesses In A DUI CaseRole Of An Expert Witness In A DUI Case

The most popular time for an expert witness to come in on a DUI case, I would say, it would be at a DMV hearing, an admin per se hearing, because most cases have these hearings. Not all cases go to trial where you might bring in an expert witness there. You’re a lot more likely to need an expert witness at a DMV admin per se hearing. In those cases, we can have experts come in and testify to the margin of error in breath testing, which is 20%, according to the defense experts, rise in blood alcohol levels. They can testify to problems with the breath machines or problems with the blood testing. They can retest the blood. They can testify about the retesting. They can testify whether there was enough preservative in the vial that held the blood.

They can testify whether there was some type of contaminant or something that caused the blood to have a higher blood alcohol level than it should have; some micro-bacteria in the vial. In some counties, like Alameda County, it’s a county where one of the labs notoriously will come up with a blood test, and when we retest it, it will be almost always 0.02 or 0.03 lower, so it’s a lab that’s been brought into question. We can have experts come in and talk about the difference in a retest and how the original test just cannot be trusted when the retest comes back so much lower.

Experts can also testify about field sobriety testing. That does depend on what they’re qualified to do. I use one who’s qualified as a standardized field sobriety test instructor. This expert can testify about all sorts of problems with the testing that someone was given, and this person can talk about how my client actually passed or did not fail field sobriety tests.

They can talk about the number of clues that were observed by the officers, based on the police report, and say, “This is not a fail of this test. It’s not a fail of that test.” The expert witnesses can talk about the circumstances that led to the arrest and detail about my client, such as: Whether it’s rising blood alcohol level or margin of error, and the lack of failing the field sobriety test and the objective symptoms of intoxication, such as if there was no unsteady gait or if the person’s demeanor was very calm and cooperative.

There are many different things that they can look at it and show that it’s more likely than not that at the time of driving, this person was under a 0.08 blood alcohol level. I’ve had a lot of success using experts, such as forensic toxicologists, at the DMV hearings.

For court, these experts would usually come in during a jury trial and testify about a lot of the same things that I already talked about. Having expert witnesses testify at trial is a lot more expensive. However, in a case where you are questioning a blood test result or a breath test result and if you have a client who can afford to pay for an expert witness to come in and testify, then you’ve got a much better chance of winning. It’s usually at least $1,500 to $2,000 to get an expert to come in and testify at a jury trial

Sometimes, I have a client who can’t afford that or doesn’t want to hire the expert, so we’ll cross-examine the prosecution’s expert who will come in and testify about the machines or the blood.

An Expert May Be Retained Prior To Trial To Examine The Evidence

Sometimes we can have an expert if we think it will really help and sometimes we have two experts testifying about different things. So, we have them write up a synopsis or a letter to us stating what they’re testimony will be and why.

We can present that to the prosecution, and that has resulted, in a past, in having cases being dismissed or charges being reduced to something that’s acceptable to a client, such as a wet reckless, a dry reckless, or some type of a moving violation. Yes, we can use them that way.

Also, experts are very useful, especially close cases, to help me evaluate a case. I’ve been doing DUI defense for over 31 years, so most of the time I’m pretty good about evaluating without needing an expert to look at it and tell me what’s going on.

There are a lot of times where I want an expert to give me an evaluation and something that I can share with my client, and just say, “These are the strengths and the weaknesses of the case, based on a scientist, based on a forensic toxicologist’s knowledge.”

Impact Of Medical Conditions On Field Sobriety Test Performance

We can use experts in those instances. Medical explanation can get very complicated when we’re talking about acid reflux. There’s a GERD defense, that’s gastro esophageal reflux disease. For that, it helps if someone’s been pre-diagnosed. If not, they can get diagnosed after getting arrested for a DUI. Experts can become very costly in one of those cases because we need to bring in the defendants doctor, or doctors, who have examined him or her and written their reports or done surgery on them. We need a forensic toxicologist who can testify as to why a breath machine would read someone’s at a 0.13 when they really were much lower, or lower than the legal limit, at the time of driving because the reflux was causing that. That’s one area for a medical defense to use an expert.

Elderly & Disabled People Performing Field Sobriety Tests

For people who may have some type of injury, disability, or just elderly, who can’t perform these tests. Yes, I can bring in an expert witness who can say that they should not have been given them.

If someone’s over a certain age, they should not be given a field sobriety test. If they have injuries, leg injuries or head injuries, they should not be given these tests. Sometimes the police officers will ask people about these, sometimes they don’t. As a defense attorney, those factors can really wipe out the results on the field sobriety tests. The juries won’t take them into consideration as much if a forensic toxicologist or an expert on field sobriety tests comes in a says, “These officers should not have given someone who’s 65-years old and overweight, or who has a bad back, a walking test. Walk a line, turn, and come back, heel to toe; standing on one leg for 30 seconds, balancing tests.” These tests are not designed for people other than people who are 20-years old and who are in very good shape and who have good balance.

For more information on Expert Defense Witness In A DUI Case, a free initial consultation is your next best step. Get the information and legal answers you are seeking by calling (415) 523-7878 today.

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Aaron Bortel
With 30 years of specialized experience in DUI defense, Attorney Aaron Bortel is a dedicated advocate for those facing DUI charges in the Bay Area. Committed to helping clients avoid jail, save their driver’s licenses and jobs, and prevent permanent criminal records, he combines deep legal expertise with genuine care for his client's welfare. Trust in a lawyer who not only defends but truly supports you through challenging times.

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