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Are DWI Blood Tests Accurate?

Texas DWI, Blood Draw, Blood Test Mimi Coffey DWI Lawyer

Some initial questions:

  • I thought DWI blood tests were automatically admitted?
  • Isn’t blood testing the gold standard?

The answer to both is NO. A judge or jury may disregard DWI blood tests. When it comes to scientific evidence, there are many factors that a court needs to consider when determining the reliability of a scientific theory or technique. While these factors apply to both civil and criminal cases, these factors might mean the difference between suppression of evidence and a conviction in criminal cases. In Texas, these factors mainly come from three cases: Frye, Daubert, and Kelly. I will go through each one briefly and then give an example based on one of our current cases.

The Frye General Acceptance Standard for Scientific Evidence

The Frye case is the oldest and most simple of the three cases. All the Frye case requires is “general acceptance” of the theory or technique among the scientific community. Though no case has expressly overruled Frye,”general acceptance” standard is not the standard anymore. However, Frye is an important building block for the other two cases.

The Four Daubert Factors

There are four Daubert factors:

  1. Whether the theory/technique can be or has been tested
  2. Whether the theory is subject to peer review
  3. The potential error rate of the theory/technique
  4. General acceptance of the theory technique

Going out of order, one of the factors is the Frye general acceptance standard. As said above, Frye is no longer the standard, but is still and important factor for courts to consider. While the other factors may seem self-explanatory, remember that science is an evolving field. Scientists make new discoveries and perform new experiments every day. Because of this, these factors are designed to prevent a brand new theory or technique from being used as authoritative science. These factors require that a theory or technique undergo enough testing to have a potential error rate and for other scientists to criticize or support the theory or technique.

The Texas Kelly Factors

Here is the big one for Texas. The Texas Court of Criminal Appeals decided the Kelly case a year before Daubert, but both have similarities. There are actually two sets of factors present in the Kelly case.

The first three factors when determining reliability are:

  • the validity of the underlying theory
  • the validity of the technique applying the theory
  • that the technique was properly applied on the occasion in question

To make these determinations, the court discussed other factors for courts to consider. These include:

  1. Acceptance by the scientific community (the Frye standard again)
  2. The expert’s qualifications
  3. The existence of literature supporting or rejecting the underlying theory and/or technique
  4. Potential rate of error of the technique
  5. Availability of other experts to test and evaluate the technique
  6. The clarity with which the underlying theory and/or technique can be explained to the court
  7. The experience and skill of the person applying the technique on the occasion in question.

As you can see, Daubert and Kelly have many similarities. Also, the Frye standard makes another unsurprising appearance. As with Daubert these factors help courts determine whether to suppress scientific evidence.

A current example of the Factors

On some of our current DWI cases, we have issues with the DWI blood tests. As a starting note, Mimi requests blood records when she feels like there might be an issue with the blood test. In this case, we sent a subpoena to the Tarrant County Medical Examiner’s office. In return, TCME gave our office a six-page summary of the validation study. Here is the issue, a summary tells us and our expert nothing about the tests or how they were performed. Our office then had the judge sign a motion to compel TCME to provide us with more records. TCME sent us more paperwork about the results, but the same six-page summary when it came to the theory and technique used.

Without the raw date to show that the machine is validated for blood testing, the results are worthless. Our expert has almost nothing to go on to come to an opinion on whether TCME used a valid theory/technique based on a six-page summary. This should trigger on of the Kelly factors (#5 above) as well as call the validity of the theory/technique in question. This six-page summary also tells us nothing about the potential rate of error or whether the theory/technique is or has been tested. In short, a six-page summary violates Daubert and Kelly. It might also violate Frye since a six-page summary doesn’t describe the general acceptance of the theory/technique.

More about Mimi Coffey & The Coffey Firm

When people look for a Top DWI Attorney or Best DWI Attorney, they look for experience, certification, and respect in the legal community. Mimi Coffey is a nationally-renowned trial attorney, board-certified in DWI by the NCDD. She has been practicing for over 24 years and is an author of multiple DWI Defense textbooks. She is also a national and state-wide lecturer on the law.

The Coffey Firm handles a wide variety of cases, including Unlawful Carrying Weapon (UCW), Assault (including family violence), and Possession charges. We can also help you try to get a DWI off your record or avoid probation revocation. The Coffey Firm offers fair DWI payment plans.

Mimi is also listed on several “top criminal lawyer near me” directory listings such as DWI Lawyers for Wise County, DWI Lawyer Tarrant CountyDWI attorney Dallas County, DWI attorneys Collin County and DWI attorneys Parker County. Mimi is a caring DWI Lawyer in DFW, She is also involved in the Texas Tech School of Law foundation and enjoys using the skills she has developed to give back to the community.