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DWI Blood Tests


In many Texas driving while intoxicated (DWI) cases, the arresting officer will demand that the driver provide a blood sample so that the state can determine whether the driver’s blood alcohol content (BAC) is over the legal limit of 0.08. These DWI blood tests in Houston, Harris, Montgomery, and surrounding counties of Texas can also determine the presence of certain illegal, prescription or over the counter drugs.

Houston DWI Blood Test Attorney

DWI defense attorney Matt Horak is experienced in defending drunk driving cases in which an individual’s blood is tested for drugs and alcohol. There are many defenses that can be used to challenge the state’s blood test results in Texas.

If you’ve been arrested for DWI and tested positive for drugs, or over the legal limit of 0.08 for Blood Alcohol Content (BAC), or if you refused to submit to a blood test in Harris, Montgomery, or surrounding counties, contact Horak Law to evaluate your case and formulate the best DWI defense strategy for your situation.

The blood test is generally viewed as the most accurate way of measuring Blood Alcohol Content (BAC). The blood test is often the only way of determining the presence of certain drugs. Yet even in blood test cases, your Houston criminal defense attorney can often contest the results or request that the entire test be excluded or suppressed by the Court.

Law enforcement officers will often demand a blood test for any DWI case involving serious bodily injury or death. In fact, even if the driver is not conscience or refuses to cooperate the officer can often demand a forced blood draw under limited circumstances.


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Issues in the Texas DWI blood test case can include:

  1. Attacking the re-calibration of the plasma blood test result to whole blood value (because without the proper recalibration new studies show the result may be overestimated by more than 50%).

  2. Showing mistakes with taking the blood from an artery instead of a vein;

  3. Moving to exclude the results if law enforcement failed to preserve two vials of blood so that retesting by the defense attorney’s expert is possible;

  4. Showing the sample was not properly taken by a qualified person such as a doctor or nurse (sometimes called “the phlebotomist”);

  5. Demonstrating problems with the mixing of the blood sample with the proper levels of chemicals that preserve the sample (anti-coagulant);

  6. Finding mistakes used by the person taking the blood if that person used a cleaning swab that contained alcohol which can lead to an inaccurate BAC reading;

  7. Irregularities with the storage of the blood sample especially when it was not refrigerated;

  8. Attacking the prosecutor’s attempt to show the procedures and timeline used by every person who touched the blood sample (also known as “chain of custody”); and

  9. Attacking the various methods of testing the sample including enzymatic, gas chromatography, and dichromate.

Just because you submit to a blood test and are arrested for DWI, does not mean that you will be convicted for DWI. It’s important to seek proper legal advice from an experienced criminal defense attorney who will stand up for your rights and best interests.


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Horak Law | Texas DWI Lawyer

If you have been charged with a DWI-related offense including DWI with property damage, serious bodily injury, intoxication assault, or intoxication manslaughter in Houston, The Woodlands, or surrounding counties of Harris, Montgomery, Fort Bend, Brazoria, Galveston, Liberty, or Waller counties, then call an experienced Houston DWI lawyer. Our office is ready to speak with you and schedule your immediate, and confidential consultation with attorney Matt Horak to discuss the facts of your drunk driving case.

Call (713) 225-8000 today to review an honest and thorough evaluation of your case.


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  • Texas Board of Legal Specialization | Criminal Law
  • National College for DUI Defense
  • National Association of Criminal Defense Laywers
  • Harris County Criminal Lawyers Association
  • Better Business Bureau - A+ rating
  • Matt Horak has earned recognition for community leadership by Lawyer Legion