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The Benefits of Using an Expert Witness in a DUI/DWI Case

An expert witness may play a vital role in a driving under the influence (DUI) or driving while intoxicated (DWI) case. You and your defense attorney are working to mitigate the severe potential damage of charges against you. An expert witness provides expert reports, testimony and evidence to assist in educating and informing the DMV officer, judge, or jury. The information is presented in a way that’s helpful to the case, towards a certain conclusion.

The Texas Rules of Evidence §§ 702-06 codify the standards required for the admission of expert testimony. The law says that testimony of an expert witness is admissible if “scientific, technical, (or other) specialized knowledge will assist the trier of fact” regarding understanding evidence or in the determination of facts of an issue.

An expert witness has specialized or technical knowledge of the specific components of evidence that the state of Texas has gathered against you. He or she can assist your criminal defense attorney in achieving the best possible outcome of your case.

Why Expert Witness Testimony is Beneficial in a Texas DUI/DWI Case

An expert witness may help members of the jury to better understand that chemical testing, breathalyzers, or field sobriety tests aren’t “iron-clad” evidence. Each test method is subject to human interpretation and errors. An expert will explain the ways in which any test is impacted by external factors and call into question the actual validity of any test results.

For example:

  1. Field sobriety testing isn’t an objective evaluation. These tests are always subject to the arresting officer’s interpretation.
  2. A chemical test, such as a urine or blood test, must be performed under strict conditions. The expert witness assists the jury in understanding how necessary standards weren’t met in your testing.
  3. Breathalyzer tests are known to be affected by many factors, such as 1) your body temperature when the test was taken, 2) how deep a breath you drew when blowing into the machine, or 3) the ambient surrounding temperature of the air when you took the test.

You may logically ask, “If that’s so, why do I need an expert to tell the jury these facts?”

The answer is simple. Some information and facts could be presented by a non-expert in a DUI case. Your attorney knows the facts, but the defense attorney can’t testify. There’s an inherent problem in using a non-expert: The judge might strike or exclude testimony offered by a layman as lacking the proper foundation. An expert witness is required to provide opinions involving any complex issue.

For this reason, your hearing requires an expert to provide qualified opinions based on experience and qualifications. You need an individual with specialized knowledge to inform the jury.

Do you need representation for a DWI charge in Texas?
Contact defense attorney Matthew Sharp for a consultation 
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When to Use an Expert Witness Regarding Property Damage in a Texas DUI/DWI Arrest

When property damaged resulted before a DUI or DWI arrest in Texas, you may benefit from an expert reconstruction of the accident scene. The jury needs to know exactly what happened, including 1) when you and the other driver(s) applied brakes and 2) how fast the vehicles were traveling to question the prosecution’s claims against you.

An expert witness may mean the difference between a not guilty or guilty verdict, or a reduced charge in a DUI/DWI case. If you’re facing a serious charge in Texas, it’s important that you engage expert witness testimony.

When to Use a Forensic Alcohol Expert Witness in a Texas DUI Case

The study of forensic toxicology involves the presence of alcohol and drugs and their effects on the human body and behavior. An expert witness specializing in forensic toxicology:

  • Testifies about the concentration of drugs and/or alcohol in an individual’s body and, given such concentration, how impaired he or she might be. Questions of impairment and intoxication are always relevant in a DUI/DWI case.
  • Provides insight regarding known flaws in blood or breath tests, such as 1) improper methods used in the analysis of a blood sample or 2) incorrect calibration of a breathalyzer device.
  • Fights retrograde extrapolation, typically offered by the prosecutor to guesstimate how many alcoholic drinks a driver or defendant consumed, or what his or her blood alcohol level (BAC) was at the time of the accident. This sort of evidence is typically based on an array of assumptions, each presenting a large range of possibilities. An expert will easily point these out.
  • Shows the prosecution has insufficient or invalid evidence, such as whether the driver had a 0.08 percent BAC at the time he or she was arrested, or whether the driver had a BAC of at least 0.01 percent if less than 21 years of age (or if he or she was on a DUI probation).
  • Argues rising blood alcohol defenses, device calibration, or maintenance errors involved with the measurements of blood and/or breath in a DUI case.
  • Testifies regarding the scientific literature, studies and state’s standards to support the defense’s case.

The prosecutor is likely to provide experts, such as forensic toxicology professions working for police crime labs. Use of expert witnesses in a DUI case is often required for complex issues like testing because these experts are deeply familiar with the current requirements for accuracy and relevant studies. He or she may be helpful in commenting on or criticizing the way drug or alcohol levels were determined.

The prosecutor must prove any elements of the DUI case beyond a reasonable doubt. An expert witness can successfully present information related to forensic alcohol tests, detections, and errors present in a DUI case.

When to Use a Police Procedures Expert Witness

Law enforcement professionals sometimes act in ways that violate the explicit procedures put forth under the law, their department rules, or their field training.
The most common violation involves the individual’s right against self-incrimination, the Miranda rights. The Miranda rights are supposed to be read by the law enforcement officer before he or she engages in a custodial interrogation:

  • If the driver or defendant make any statements, confessions, or admissions without these warnings while in detention or custody, a knowledgeable criminal defense attorney can motion to exclude the statements as evidence.
  • An experienced Houston DUI lawyer will obtain DUI police procedures regarding contact with the driver, observation, field sobriety tests, and methods used to collect evidence. An expert witness can provide additional insight regarding any violations of police procedures, issues with alcohol detection/procedures, and standard of care violations as well as whether the defendant was placed under lawful arrest.

When to Use a Field Sobriety Test Expert Witness in a TX DUI Case

Field sobriety test experts can authoritatively comment on the proper administration of test(s) given to an accused. He or she points out mistakes made by an arresting officer.

Police officers receive training in stopping suspected drunk or impaired drivers, alcohol detection, and conducting field sobriety testing in just one training course: the National Highway Traffic Safety Administration (NHTSA) FST course (NHTSA manual).

  • The course strictly follows procedures to be used in the collection of each type of field sobriety test.
  • These procedures match and calibrate to specific validation studies correlating specific behaviors and test performance at 0.08+ percent or 0.10+ percent BAC.
  • The NHTSA FST materials used to train officers across the United States say if the test isn’t given “exactly as trained or instruction,” the results may be invalid.

Not all police officers perform these tests precisely or perfectly in all conditions. This fact may be used to demonstrate to the judge or jury that a test may be considered invalid because it wasn’t used according to design. An expert witness in a TX DUI case can also help the defense to prove that the prosecutor can’t meet its burden of proof.

When to Use a Field Sobriety Test Expert Witness in DUI/DWI DRUGS Cases

A case involving driving while impaired may benefit from the involvement of a Drug Recognition Expert (DRE). A DRE is a police officer extensively trained to detect a variety of illegal and prescription drugs. He or she typically gathers evidence to support DUI/DWI charges.

Using an expert witness in a DWI case involving drugs lends the professional DRE’s authority as an expert. His or her training and experience can be invaluable in explaining particular behaviors, such as a rapid pulse or sweating, exhibited by a driver suspected of DUI/DWI.

When to Use a Mechanical Expert Witness in a TX DUI Case

A mechanical expert may be beneficial in a TX DUI case as well as a personal injury or product defect case.

In a DUI case, the defendant’s alleged poor driving behavior may be used to justify the police’s decision to stop him or her on a suspected DUI:

  • Vehicular issues, including alignment, brakes, wheels, suspension, or tires may have caused “poor driving behavior.”
  • The mechanical expert witness can assist with probable cause when a motion to suppress evidence and dismiss is presented before trial.
  • He or she can show there was an insufficient probable cause, supporting the defense’s case.
  • He or she can elucidate breath testing issues. Breathalyzer tests may yield false positives in a DUI case. If the driver was involved in an accident that deployed the vehicle airbag(s), these frequently scatter “airbag dust” which can mimic the presence of alcohol in a breathalyzer device.
  • Airbag dust from certain model cars contains acetone, which could be present in the driver’s mouth or skin, inhaled into the lungs, and appear as a false positive breath test.
  • Breath test results may be invalid. The prosecutor must prove beyond a reasonable doubt that the driver was operating a motor vehicle with a 0.08 percent BAC at the time. An expert witness can present the measured results weren’t actually alcohol, or show other factors that contaminated the defendant’s test to the extent that the results aren’t useful or meaningful in deciding the case.

Although an expert witness might not be compulsory, he or she can be extremely helpful in court when used in combination with the skills of an experienced Houston DUI attorney. If a defendant is accused of a DUI/DWI, the right expert witness can educate and refute the prosecution’s case.

DUI in Texas

According to the Texas Department of Public Safety, a DUI conviction is expensive and has potential long-lasting consequences. A first offense can involve a maximum $2,000 fine, three to 180 days behind bars, a loss of driver’s license for up to 12 months, and annual fees between $1,000-2,000 for three years to keep the driver’s license after it’s reinstated.

A second DUI conviction involves a maximum $4,000 fine, one month to one year behind bars, a loss of driver’s license for up to 24 months, and annual fees of $1,000-$2,000 for three years to keep the license after it’s reinstated.

A third DUI conviction involves a maximum $10,000 fine, two – 10 years behind bars, a loss of driver’s license for up to 24 months, and annual fees of $1,000-$2,000 for three years to keep the driver’s license after reinstatement.

  • If you have two or more DUI convictions in a five-year period, the installation of a special mini breath test device on your vehicle is required. The device costs about $100.00 per month.
  • You must pay for DUI/DWI Education in Texas if convicted. Depending on the education program mandated by the court, you may pay surcharges of $1,000-$2,000 per year for three years.
  • You must pay reinstatement fees of your driver’s license after a DUI conviction in Texas. The charges to reinstate your license are at least $125.
  • After a DUI/DWI conviction in Texas, your car insurance premiums will rise. Changing carriers probably won’t help.
  • Don’t forget about the impact of a DUI/DWI conviction on your job. You could lose a good job. A DWI conviction in Texas leaves a permanent record. You’ll also need time off to serve your jail sentence and meet with a community supervision officer if the court orders probation.
  • Other possible costs include 1) post bond or bail (several hundred to several thousands of dollars); 2) towing and impound fees ($100-$200); possible house arrest and electronic monitoring; and more.

The Real Cost of a TX DUI

The real cost of a DUI in Texas depends on the facts of your case, how many prior offenses you have, and the experience of your DUI attorney.

Reach out to a knowledgeable Texas DUI lawyer now. It might be possible to minimize the costs and penalties of a DUI—or even have your case dismissed. Contact The Law Office of Matthew D. Sharp to discuss your matter now at 713-868-6100.

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