Using an expert witness in a DUI case

An expert witness can be helpful in a DUI case to help provide proof in support of defenses that require particular specialized knowledge. Using an expert witness in a DUI case can be extremely helpful in proving a number of issues, as discussed below.

The primary purpose of any expert, when hired by either side, is to educate – that is to provide evidence in the form of an expert report and/or testimony that educates the DMV hearing officer, or the judge, or even the jury, in a way that presents information that is helpful to a client, towards a certain conclusion.

Some of the information you might want to present in a DUI case could be presented by someone who is not an expert.  The problem with using non-experts is that a DMV hearing officer, or a judge hearing the case, might exclude or strike down layman testimony as lacking proper foundation or requiring an expert witness to give an opinion as to any complex issue that requires an expert. For that reason, courts and other hearings require experts who can provide their qualifications, experience, and opinions.

There are also reasons in a DUI where you will want an expert witness as a strategy in defending a DUI case. Using an expert witness in a DUI case can give particular testimony extra weight, authority, and emphasis.  

Expert witnesses are also subject to cross examination by the other side.

The law on who is an expert witness, and what they can testify to.

California Evidence Code section 720 contains the authority under the law, defining what an expert witness is, and what they can testify to:

720.  (a) A person is qualified to testify as an expert if he has special knowledge, skill, experience, training, or education sufficient to qualify him as an expert on the subject to which his testimony relates. Against the objection of a party, such special knowledge, skill, experience, training, or education must be shown before the witness may testify as an expert.
   (b) A witness' special knowledge, skill, experience, training, or education may be shown by any otherwise admissible evidence, including his own testimony.

Using a forensic alcohol expert witness in a DUI case at the DMV and in court

Forensic toxicology is the study of the presence of drugs or alcohol and their affects on the human body and human behavior. A forensic toxicologist, therefore, is able to testify about the concentration of alcohol and/or drugs in a person’s body and how impaired that person might be, given such a concentration. Using an expert witness in a DUI case that knows about intoxication and impairment, key issues in any DUI is always helpful.

A toxicology expert may also testify about flaws in breath or blood tests, such as an incorrectly calibrated breathalyzer machine or the use of improper scientific methods during the analysis of a blood sample. The prosecution will usually also provide their own experts, including forensic toxicologists who work in crime labs for the police. Testimony provided by each side’s experts can and often does determine the outcome in a DUI trial, so it is imperative to have qualified experts on your side.

Using an expert witness in a DUI case may be required for certain complex issues. As a science, blood testing and breath testing is the domain of experts who are familiar with the studies and requirements for accuracy.

An expert can be extremely helpful in that the expert can comment on, and possibly criticize, the way in which an alcohol or drug level was determined in a DUI class. They can outline the way why those results might be inaccurate. This can include incorrectly calibrated breathalyzer machines, incorrect use of the machinery, or inexact scientific methods of blood analysis. A common use of an expert witness in a DUI is to fight the retrograde extrapolation typically presented by the prosecution – which is often improperly used to speculate as to how many drinks the defendant or driver consumed, or might be used to estimate what the blood alcohol level was at the time of driving for the defendant.  That evidence is often based upon a number of assumptions, each with a wide range of possibilities, that the expert can easily point out.

Using an expert witness in a DUI case at the DMV, can lead to a showing that the DMV has insufficient evidence, or invalid evidence, as to one of the relevant issues at a DMV hearing — include the major issue of whether the person was above a .08% alcohol level at the time of driving, or whether the person was above a .01% if under the age of 21 or if on DUI probation.  Rising blood alcohol defenses, or errors in the maintenance, calibration, or measurement of breath or blood in a DUI case, is best presented through an expert witness.

In court, all elements of a DUI must be proven beyond a reasonable doubt. Showing a judge, jury, or prosecutor an expert witness report detailing facts supporting a rising blood alcohol defense, impairment of drugs (and interactions between drugs, or with alcohol) for DUI Drug (DUID) cases,  or showing any errors in the maintenance, calibration, or measurement of breath or blood in a DUI case, is best presented through an expert witness, who can also testify to the state’s standards and the scientific literature and studies that support defenses in the case.

In most cases, our Orange County DUI attorney uses Henry Greenberg, of Forensic Analytical Consultants, here in Orange County, although we have used and consulted with expert witnesses Dewayne Beckner, Daryl Clardy, and Okorie Okorocha, as to forensic alcohol testing, detection, and error issues.

Using police procedures expert witness in a DUI case

Often, police will act in a way that violates their training, or explicit procedures under the law, or the rules from their own department.

The most common one known by almost everyone is the right against self-incrimination – the Miranda rights, read by police before any custodial interrogation.  Any confessions, or admissions, or statements, that were made without these warnings while in custody or detention, can be the subject of a motion to exclude those statements as evidence.

More importantly for a DUI case in court, or at trial, our Orange County DUI Lawyer will obtain the DUI police procedures as to observation and contact with a driver, field sobriety testing, safety of the officer and the testing subject, and the methods of collection of evidence to be used in the case, can be testified to by an expert.

With DMV hearings in a DUI case, one of the issues at the DMV hearing is whether or not the officer followed all the procedures and laws to place someone under a “lawful arrest”.  The issue of whether that occurred or not can be the domain of an expert witness opinion also.

Our DUI attorney Orange County has used expert witness Dewayne Beckner, who used to train police officers in his role as leader of the Los Angeles County Sheriff’s Department alcohol detection unit, for testimony related to violations of police procedures, the law or standard of care violations, and problems with alcohol detection and procedures.

Using a field sobriety test expert witness in a DUI case

A field sobriety test expert can comment on the validity of the administration of the test or tests are given to the accused and point out any mistakes that may have been made by the arresting officer.

With DUI cases, officers are trained in alcohol detection, stopping potential drunk drivers, and conducting field sobriety tests using one standard training course – the NHTSA approved FST student course, using the NHTSA manual.  That manual and course strictly follow the procedures for each field sobriety test, which matches, and are calibrated to, the validation studies that correlated certain behaviors and test performance with being above a .08% or a .10% alcohol level.

As it states in the NHTSA FST manual used to train all officers in the USA, if the tests are not given exactly as trained or instructed, the test results may be invalid.

Although police who are on DUI saturation patrols or make DUI arrests and conduct DUI testing are trained to follow the field sobriety tests, not all police officers do the test perfectly, under all conditions.  That can be used to show a judge, or a jury, that the test should be considered invalid because it was not utilized as it was designed to be given.

Most forensic alcohol experts can also testify as to the field sobriety tests, the standardized FST testing procedures, the history of the FSTs, the validation studies, and how they should be done correctly.

Using an expert witness in a DUI case can also help you prove that the DMV cannot meet their burden of proof. At the DMV, one of the issues that must be proven is whether or not the DMV has proven that the police had sufficient probable cause to conclude that a person was impaired, and to arrest.  That is usually shown through the FSTs, so pointing out via an expert how those tests were done incorrectly can help win the DMV hearing.

An expert witness for these issues can also be another DUI defense lawyer, as another DUI lawyer Orange County that specializes in DUI are certified in field sobriety testing at the student level, and have taken the instructor FST course, and have reviewed hundreds, sometimes thousands, of field sobriety tests.

Using a field sobriety test expert witness in a DUI drugs (DUID) case

Cases involving Driving Under the Influence of Drugs (DUID) usually involve a DRE – a “Drug Recognition Expert”.  This is a police officer that has gone through more extensive training to detect a wide variety of prescription and illegal substances, towards gathering evidence to support a charge of driving under the influence of any controlled substance or illegal substance.

That could be a case for driving under the influence of marijuana, driving under the influence of Ambien or other sleeping medication, driving under the influence of any illegal drug, or driving under the influence of any of a number of prescription drugs.

Using an expert witness in a DUI case involving drugs happens in every DUID case. The prosecution qualifies and uses a DRE police officer as an expert – their training, and experience with cases usually allow the court to recognize them as one.  Countering that with a drug recognition expert of our own, as the defense might help explain the behavior that the DRE uses as evidence of impairment through drugs.  In many cases, there are other explanations of particular behavior.  Sweating, a rapid pulse, or other behavior might be explained, at least in part, by the nervousness from being pulled over by the police.

Like field sobriety test experts, anyone with equivalent training to the police DRE expert in a DUI drugs (DUID) case can counter the evidence at trial, or at the DMV. Certain medical expert witnesses (see below) can also be helpful, or can be used, to testify as to the effects of stimulants, depressants, psychedelics, and the interactions between various types of drugs or medicines, as well as how long the drug might stay in the system, and at what levels a person might be impaired.

Using a mechanical expert witness in a DUI case at trial

In some cases, a mechanical expert might be appropriate.  In civil cases, including product defect cases and personal injury cases, mechanical experts are very common.  Mechanical expert witnesses are used to being hired by lawyers and providing expert testimony at depositions, or at trial.

Driving, especially poor driving behavior that was used by the police to justify a stop for suspicion and investigation of DUI, can sometimes be caused by problems with a vehicle’s brakes, suspension, tires, wheels, or alignment.  That can help with the issue of probable cause in a motion to suppress evidence and dismiss before trial, a not guilty on your DUI at trial, and can help to show that there was not sufficient probable cause to win your DMV hearing.

Using an expert witness in a DUI case can help explain not only probable cause but also breath testing issues.  When it comes to a false positive in a breathalyzer test for DUI cases, being involved in an accident that caused the vehicle’s airbag to deploy can often scatter airbag dust, which, through the Tyndall effect, can mimic alcohol in a breath machine.  That dust contains acetones, which can be on the skin, in the mouth, and inhaled in the lungs, and which show up as a false positive for alcohol in breath tests during a DUI arrest.

The airbag dust acetone dust only exists on certain model cars, however, so a mechanic familiar with vehicles and airbags, or any mechanical expert that can give an opinion on the subject, might be enough to create reasonable doubt at trial or at a motion to dismiss in court.

With the DMV hearing in a DUI case, it may also be used to show that the breath test results are invalid. It is an essential issue and part of the requirement under the DMV burden of proof that the DMV shows that a licensee was above a .08% at the time of driving.  An expert can show that the results measured were not truly alcohol, or that other factors contaminated the test to an extent that the alcohol test is not meaningful or useful in the case.  That can win a DMV hearing.

Using an accident reconstruction expert in a DUI case

An accident reconstruction expert is also a common expert witness for civil and personal injury depositions and trials.  Using an expert witness in a DUI case to describe how an accident occurred in detail can help the defense. This type of expert may be used to generally describe and explain how any accident in question occurred, based upon the evidence from the road, the vehicles, and witnesses. In a DUI with accident case, it can show that the accident was not the fault of the driver, in some cases.

The expert may also be able to estimate the speed of the vehicles at the time of impact, find out when the brakes were applied, deduce how fast each vehicle was going before and after impact, and other relevant details that refute or cast doubt on the claims made by the prosecutor.  If an accident was found to be someone else’s fault, that may help mitigate the damage in a DUI case in court, at trial, or at sentencing.

Using a medical expert witness in a DUI case

Using an expert witness in a DUI case for explaining medical issues, symptoms, and effects can help. The are many issues where a medical expert might be helpful in a DUI case.

In breath testing involved in a DUI case, known medical issues such as the creation of alcohol by the body, gastric bypass surgery, acid reflux disease or GERD, or mouth alcohol from dental work, might be a contaminant that can cause a falsely higher reading for alcohol.  Certain conditions, like diabetes, being on a ketogenic diet, or even having aspirin in your system, can falsely inflate the alcohol reading, above the true reading. The driver’s lung capacity, which might have been reduced from smoking, exposure to pollution, or surgery, can also be relevant to a breath test.

With a DUI blood test, a medical expert can testify as to bacteria in the vial, DUI blood testing issues, and defenses, chain of custody or refrigeration of the blood sample, and the correct way to collect or draw blood.  Using an expert witness in a DUI case can cross over to what can be the domain of other expert witnesses. For example, in a DUI case involving alcohol consumption, a phlebotomist is not supposed to use an alcohol swab on the arm before drawing blood, as that can contaminate the sample and prevent measurement of the true reading from the blood.  That is known by both the forensic alcohol community, and the medical community.

With field sobriety testing, a medical expert can testify as to balance issues caused by knee, back, ear/equilibrium, knee, or ankle problems, can testify as to neurological reasons why nystagmus or other symptoms might be present, and can testify as to lung capacity or physical problems that may be relevant

Using an expert witness in a DUI case for more complex medical issues doesn’t have to be expensive either.  A medical expert witness in a DUI case can be the driver’s treating physician, or any specialist with relevant knowledge, who can testify regarding the particular medical issue involved in the DUI case.

When using an expert witness in a DUI case, can the jury be told that you paid an expert witness to give his or her opinion?

Yes.  Using an expert witness in a DUI case can result in the jury being told that the expert was paid by the defense. Under Evidence Code 722 in California, it states:

722.  (a) The fact of the appointment of an expert witness by the court may be revealed to the trier of fact.
   (b) The compensation and expenses paid or to be paid to an expert witness by the party calling him is a proper subject of inquiry by any adverse party as relevant to the credibility of the witness and the weight of his testimony.

Of course, expert witnesses do not work for free, so it’s natural for a DMV hearing officer, a judge at a hearing, or at trial, or a jury to expect that an expert would be compensated for reviewing evidence and providing testimony as an expert.

Could an expert witness in your case be stopped from testifying?

According to Federal Rule of Evidence Rule 702: Testimony by Experts, under the Daubert standard, any testimony supplied has to be based on sufficient facts or data and must be produced and applied through reliable methods and sound principles by the expert. If it meets that criteria, it will then, as Rule 703 says, be regarded as evidence.

In California courts, Evidence code section 352 allows a judge to weigh how helpful the testimony is, against how prejudicial it might be to a fair trial.  The judge makes the final call as to whether or not the testimony comes in, or whether it’s limited as to what the expert can say.  Using an expert witness in a DUI case usually is allowed, as DUI cases rely on scientific evidence and testing, as well as more complex issues.

Although an expert witness may not be free or compulsory, they can be very useful, and helpful, in court, or at the DMV, and with proper use by the best DUI lawyer,  they can help win DUI cases.

Contact us for questions

Contact our firm if you have any questions about the use of expert witnesses in a DUI case.  We have much experience in this area, and are happy to help you win your case in any way that we can.