Generally, in Texas driving while intoxicated (DWI) cases, drivers undergo breath testing to find out whether they are illegally intoxicated per se while driving in a public area. Put otherwise; breath testing will show whether the driver’s BAC (blood alcohol content/concentration) is .08% or more. Sometimes, however, a police officer will opt for blood testing. This usually occurs when a motorist is unconscious, declines to undergo breath testing, or is suspected to be intoxicated by drugs, including over-the-counter or prescription medications.

The Blood Testing Process

Blood testing for DWI is when a qualified individual draws your blood, often at the hospital, police station, or any other stipulated location, and tests it through the gas chromatography process to determine your BAC level. Blood tests are typically more accurate when administered correctly than DWI breath tests. Therefore, most suspects, knowing the problems with breath tests, agree to blood testing— not knowing there are just as many problems with blood tests also.

If suspected of DWI, a police officer may need you to undergo blood testing. The blood testing procedures, rules, and requirements in DWI cases are governed by Texas Transportation Code 724.012.

Firstly, this Code provides that a police officer might request to draw someone's blood sample if that individual is arrested. The officer has reasonable suspicion to trust the individual was under the influence while driving a car in a public area. The law enforcement officer should request that an eligible party draw the specimen in a tidy place. Per Transportation Code 742.017, individuals eligible to draw a blood sample include technicians, chemists, physicians, licensed vocational nurses, or registered professional nurses.

Implied Consent and Refusal to Draw Blood Sample

Transportation Code 724.012 provides that a motorist agrees to blood or breath testing by being arrested for DWI. Therefore you can decline a blood or breath sample to be drawn before an arrest. After an arrest, you can decline to undergo blood testing, but if the officer has obtained a search warrant for your blood, you will be subject to administrative consequences. Texas implied consent law provides that drivers in Texas automatically agree to chemical testing once they have been arrested.

If you refuse to submit to a blood test before a DWI arrest, the officer may suspect you have something to hide and place you under arrest. If you are already under arrest and declined to give a blood sample, the police officer must acquire a blood search warrant to have you draw a blood sample. Once this warrant has been issued against you, you must comply with it. This means you cannot refuse to draw blood, and you will face administrative penalties if you do.

The law enforcement officer must properly obtain the search warrant to draw blood. If the police officer in your case does not correctly acquire a blood search warrant, the court may suppress the blood test results as evidence. A skilled and knowledgeable DWI lawyer would know how to challenge scenarios where blood samples were drawn without a blood search warrant.

A blood search warrant authorizing a law enforcement officer to draw someone's blood is an evidentiary one per the Texas Code of Criminal Procedure Art. 18.02(10). This law provides that an officer must:

  • Obtain a warrant signed by a magistrate, not a municipal judge or justice of the peace.
  • Prove that the evidence to be obtained (for example, blood sample) will be necessary to demonstrate a DWI crime.
  • Avail an affidavit to accompany the search warrant request that they established enough probable cause indicating the supposed suspect drove while intoxicated (for example, poor field sobriety test results).

It is worth repeating that the state's implied consent statute applies only to post-arrest tests. Before an arrest, you need not agree to field sobriety, breath, or blood tests. Whereas a police officer may request you to take voluntary field sobriety tests, you are entitled to decline. On the contrary, being arrested for DWI, and declining to undergo chemical testing will lead to administrative penalties.

The consequences for refusing to submit to blood testing depend partly on whether you have a prior DWI conviction or refusal on your criminal record. A first-time refusal is punishable by a driver's license suspension for 180 days. Subsequent refusals are punishable by a license suspension for two years.

You will receive a driver's license suspension notice if you refuse to take a blood test. You only have fifteen days from the date you receive the notice to appeal the suspension. Failure to appeal will lead to the suspension taking effect automatically after the fifteen days elapse. An experienced criminal defense lawyer is your ideal option to prevent the suspension of your license.

Administrative license suspension for refusing to submit to blood testing is a distinct legal action from DWI criminal charges. Put otherwise; you could still be charged with DWI even if you declined to give a blood sample. The prosecution may resolve that they have sufficient evidence to file DWI charges without a blood sample. Although, in some instances, they could decide otherwise, dropping the entire case. And if charged with DWI and proven innocent, you will still face administrative penalties for blood testing refusal. You need a skilled defense attorney to defend your rights if accused of blood test refusal.

Choosing Between a Blood and Breath Test

If you decline to provide a breath specimen and the police officer obtains a search warrant to draw a sample for testing, you are not entitled to select if the sample is for blood or breath. Usually, blood testing is more accurate than breath testing; thus, you want to keep this in mind. If you refuse to give a sample and the officer obtains a warrant, they could force you to provide a blood specimen.

When Blood Testing Is Mandatory

Whereas you can forego DWI blood testing in favor of a breath test, various situations permit police officers to conduct a compulsory blood draw. Per Texas Transportation Code 724.012, these factors can lead to an almost instant blood search warrant and consequent mandatory blood testing:

  • You had a minor passenger in the car when operating a vehicle while intoxicated.
  • There was a crash, and someone passed away or was severely hurt, and the police officer had reason to believe you were operating the vehicle while unlawfully intoxicated.
  • You have been sentenced before for any two prior DWI cases.
  • You were convicted of a felony DWI, including Intoxication Assault, DWI with a minor passenger, or the Intoxication Manslaughter offense.
  • You were unconscious and are considered to have consented if you passed out.

Therefore, for better or worse, an officer can draw your blood sample without your permission (though not without a blood search warrant). Whereas these situations might require a compulsory blood draw, an officer still has other options to obtain an on-the-spot blood sample.

Drug Driving While Intoxicated Blood Tests

Suppose you are suspected of driving while intoxicated, submit to breath testing but blow below the stipulated BAC limit of 0.08%, or there is no evidence of alcohol impairment. In this case, the police officer will likely request you to submit to chemical blood testing to determine whether there is evidence of controlled substances or drugs. The blood specimen will be tested for various drugs, including, though not limited to, marijuana, heroin, cocaine, meth, opiates, and medication without or with a valid prescription.

The issue with testing blood for controlled substances or drugs after a suspected DWI is blood tests do not accurately indicate when the supposed offender was under the influence of the substances. Even though the tests are often reliable in revealing drugs and drug metabolites in the blood, the drugs might have been in the supposed offender's bloodstream long after they were no longer intoxicated and could drive safely.

Blood Test Documents in a DWI Case

In DWI cases, prosecutors will usually use blood test documents to seek the admission of BAC testing results during trial. Your lawyer can also review the evidence to know how it was obtained, analyzed, or kept.

Before any trial or hearing, your lawyer will carefully inspect all documents associated with DWI blood testing. These documents would include the following:

  • The test results in a lab report.
  • Any tests for detecting controlled substances or a detailed screen and all the necessary documentation available if another facility conducted the tests.
  • The testing agency's name.
  • The name of the testing criminalist or technician.
  • The name of the technician or nurse who extracted the blood sample.
  • The chain of custody.
  • The blood testing checklist.
  • The DIC warning sheet.

Common Problems With Blood Testing for DWI Cases

Blood tests are usually more accurate than breath tests. Even so, these tests have inherent problems just like human-made ones. Therefore, you should not assume that since the blood test results say one thing, it must be true. Common problems with blood testing in DWI cases include:

Collection and Storage of Samples

For blood samples to be error-free, they should be collected on time, and storage should maintain integrity. However, this sometimes is not the case. Firstly, the BAC content in someone's system rises with time. If arrested, transported to the station, and particular circumstances prevent the immediate drawing of blood (for example, waiting for the approval of a warrant), your BAC can be higher by the time you take the test compared to how it was when you were operating your car.

Complicating the time element further is the metabolization element. No two people can metabolize an alcoholic beverage at the same rate— small-bodied individuals process alcohol quicker than big-bodied individuals. The time between drinking an alcoholic beverage and peak BAC level also varies. It could be you drove during or before the period your BAC rose. This matters since it is likely that you were not intoxicated when you drove or when you were arrested. Therefore, timely blood withdrawal is critical to the prosecutor's case, and anything less than that must be disclosed and argued.

Secondly, blood drawing is considered a medical process, but most times, this task is done by a person with little medical experience. Minimal comprehension of the process can lead to mistakes that affect the blood sample's integrity, making it another issue with blood tests.

Thirdly, how blood samples are stored matters— the sample should be kept properly by the various persons who handle it. Improper storage may affect the sample's integrity. Improper storage or delays can give rise to conditions that enable fermentation— a process for alcohol formation. If fermentation happens, the alcohol amount in the blood sample will increase, resulting in a falsely high BAC level.

Chain of Custody

DWI blood specimens go through many hands before they are tested. Some people may fail to do a particular necessary detail of their obligation when handling a blood sample. For example, a person may fail to seal the sample correctly; another might mislabel it, while someone else might delay transporting it from one area to another. Whatever the mistakes are, irrespective of whether they were done by just one or several people, they can translate to a contaminated specimen, meaning the results could be false.

The Test and Its Results

Usually, blood specimens are tested for BAC by a machine called a Gas Chromatograph. However, the results after this process can be less definitive and more presumptive. The gas chromatography process is complex. In simple terms, however, it involves the following steps:

  1. The testing technician transfers blood into a vial. The vial should be half-full.
  2. They heat the vial.
  3. Alcohol evaporates. Theoretically, the air occupied by the unoccupied space in the vial contains the proportionate alcohol amount that could be detected in your bloodstream.
  4. The technician uses a syringe needle to take the air sample. Theoretically, the specimen in the syringe has alcohol molecules that contain the proportionate alcohol amount detected in the bloodstream.
  5. The technician transfers the sample using transfer gas to a part of the machine called a column. A flame burns the sample contents in the column, the reaction is measured, and a computer program processes the data.
  6. The test technician generated the Chromatogram report. However, the report is intricate and usually misunderstood. Only an experienced lawyer can interpret it. That is why you want to have a skilled lawyer defending you. Many defense lawyers agree that the test results are factual, but a knowledgeable one understands this is only true in some cases and may discover problems through analysis and investigation.

Apart from inherent potential issues with the blood testing itself, the test results may be affected by delays in blood sample collection or with samples contaminated through fermentation. Concerning the former, some prosecution attorneys will try to rectify the timing issue through retrograde extrapolation, a procedure used hours after to establish blood alcohol content. An officer will need specific info from you for the process to work. The information includes the time you last drank, your weight, and the duration of drinking.

The officer does not inquire about other circumstances that might influence your blood alcohol content level, like your sex, health, or the food you had eaten before driving. Also, if fermentation occurred, this device cannot distinguish or determine if the process led to the BAC results or if the results were from the alcohol in your system before fermentation.

You Need a Skilled Attorney to Challenge Your Blood Test Results if Charged With DWI

If you do not want to be convicted of DWI, you need an experienced lawyer to fight for you. An attorney who does not regularly challenge and handle DWI blood testing cases may not understand how to challenge a DWI blood test. A skilled attorney knows local police units plus the tactics every unit applies to obtain blood samples. A skilled DWI attorney also knows local judges and prosecutors. Lastly, a skilled DWI attorney understands the DWI blood testing procedure, can interpret the chromatogram report, and identify problems.

A knowledgeable lawyer can challenge blood tests through various means where some are technical, while others do not require scientific knowledge. Based on the problems with DWI blood tests listed above, a knowledgeable lawyer can draw the most solid arguments against the tests' reliability, accuracy, or validity. These arguments include the following:

  • Skin cleaner challenges
  • Blood vial challenges
  • Equipment calibration problems
  • Distorted readings
  • Issues with the handling of the blood sample
  • Chain of custody mistakes and gaps
  • The person who administered the test was unqualified
  • The testing was not done in a hygienic place
  • The test administrator was negligent
  • The blood specimen was contaminated
  • The police did not probable cause to stop you

Contact an Experienced Fort Worth DWI Defense Lawyer Near Me

At Fort Worth DWI Defense Lawyer, we dedicate our capabilities and resources to protecting our clients’ legal rights. We boast decades of expertise and a high reputation we have earned in courtrooms for successful outcomes. If accused of driving while intoxicated in Fort Worth and your blood sample was drawn to determine your BAC, call us at 817-470-2128 for legal advice and representation. We will thoroughly review the blood testing process and your DWI case before we can answer your questions and concerns.