Blood Testing

When you are stopped by law enforcement and suspected of DWI, things can happen quickly. Before you know it, you are performing Standardized Field Sobriety Tests and find yourself confronted with the ultimate question – do I consent to a blood test? What’s more, most Texas police departments have implemented no-refusal policies regarding blood tests, which means they will apply for a warrant to get your blood upon a refusal.

When you hire The Wilder Law Firm, you will be putting more than 25 years of experience working with DWIs to work for you. We have defended thousands of DWI cases and have received extensive training in the field of blood testing at Axion Analytical Labs in Chicago, and know what to look for when evaluating a blood test. As a criminal defense team, we know what to look for in fighting a blood test case and will take the time to make sure all aspects of your case and blood test are thoroughly investigated. We have the experience, knowledge, and skill that you need during this difficult time. Call us at 469-551-8609 and get the help you need today.

What is a Blood Test?

The most common type of blood testing is done by injecting a blood sample into a Gas Chromatograph Instrument. The sample is heated, and much like steam that rises above boiling water, a gas will rise above the blood and will actually be tested for an alcohol concentration. The gas travels through the column in the instrument and during this time, each individual substance in the gas will be separated out into their individual compounds. At the end of the instrument, there is a flame ionization detector that will then measure the amount of each substance found. Thus, it determines the amount of ethanol contained in the sample.

More and more police departments are no longer requesting breath tests and will only give you the option of consenting to a blood test. Additionally, what used to be the holiday No Refusal Weekend has turned into just no refusals when arrested for DWI. This means if you do refuse, the police will apply for a warrant to get your blood.

How We Challenge Blood Tests

There are many issues surrounding blood testing that we will investigate in order to discredit or suppress the results. A number that is put on a lab report does not tell the whole story. There is an entire blood testing process that needs to be investigated, and that starts with the legality of the blood draw, either by consent or warrant. When I defend you, these are some of the issues that will be investigated:

  • Consent.
  • Warrants.
  • Arterial blood vs. venous blood.
  • Whole blood vs. serum or plasma.
  • Fermentation in the blood tube.
  • Sterilization of the arm.
  • Coagulation.
  • Contamination.
  • Switched/mislabeled vials.


If you consented to a blood test, that consent must be freely and voluntarily given. The police can apply for a warrant if you refuse (Judges do not always grant blood warrants), but telling you they will get a warrant if you do not consent can render your consent invalid and the entire blood testing process could be suppressed.


If you refused a blood test and a warrant was obtained, we have to fight the warrant. Did the officer accurately describe your conduct in the warrant? The officer has to swear in an affidavit to all the facts and circumstances contained in the warrant. Any misrepresentation of a fact in the warrant could invalidate the warrant, resulting in the blood test being inadmissible. I had a Judge stop a trial and appointed a Trooper a lawyer in the middle of trial for all the inaccurate sworn statements he made in the blood warrant affidavit.

Arterial Blood vs. Venous Blood

Most blood samples will be drawn from a vein. However, the alcohol concentration in venous blood can differ from the concentration in arterial blood, depending on whether the person is still absorbing or just eliminating alcohol. Thus, venous blood results can be misleading. Arterial blood is more likely to have a higher alcohol concentration than venous blood when a person is still absorbing alcohol. Arterial blood is more likely to have a lower concentration than venous blood when the person is eliminating alcohol.

Whole Blood vs. Serum/Plasma

Blood samples tested in a hospital setting are serum tests, and serum tests for an alcohol concentration are roughly 18% higher than whole blood samples.

Fermentation in the Blood Tube

Candida Albicans is a microorganism and can cause blood to ferment, thus producing more alcohol in the sample over time. The vial the blood is stored in is supposed to contain Sodium Fluoride, which is designed to preserve the integrity of the blood sample and prevent fermentation. So we need to know if the correct classification of vial was used.

Sterilization of the Arm

Close attention to how the arm was sterilized is extremely important. Alcohol swabs should never be used for an alcohol blood draw, for it could provide an inaccurate concentration that would be higher than what was actually in the blood.


Coagulation occurs when the blood starts to clot, which means it starts to solidify. Clotting can produce a higher alcohol concentration in the liquid blood left over, thus giving an inaccurate higher result. Potassium Oxalate is a common anticoagulant used in blood vials for alcohol testing to try and prevent clotting.


Contamination can occur if blood is drawn in a non-sterile environment. The puncture site, equipment used, and vial all have to be evaluated to ensure the blood draw was done in a sterile environment. A non-sterile environment can not only affect the results of the blood test, it can also affect the admissibility of the blood results.

Switched/Mislabeled Vials

Over the years, there have been many reported cases of chemists switching vials. That means the results of someone else’s blood test are reported as your result. Additionally, vials have to be properly marked and labeled to ensure any results obtained are reported to the correct person. 

Protecting Your Freedom is Our #1 Priority

When facing a DWI with blood test results, you need The Wilder Law Firm fighting for you. Your alcohol concentration only tells part of the story and it does not mean you will be convicted of the DWI. We will challenge the admissibility and validity of your blood test results and will use our knowledge and skill to most effectively defend you. Contact us at 469-551-8609 and let us fight for you.

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We are passionate and determined about what we do, and we fight for our clients. If you’ve found yourself or a loved one in trouble, don’t give up hope. We have a criminal defense attorney who can help.


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