Because of the accuracy, the results of the DWI blood test can be the most difficult to fight in court.
A breath test for alcohol is easier to fight, but the arresting officer has the discretion to determine the type of sample used to support the charges of DWI. Also, if you refuse a breath test, the officer can require a blood sample for alcohol testing.
These tidbits are just a few of the things you need to know about DWI blood tests in Texas.
Legal Blood Alcohol Regulations
Texas considers an adult to be too intoxicated to operate a motor vehicle or watercraft safely in a public place if they have a blood alcohol concentration (BAC) of 0.08 or higher. A minor cannot have any alcohol in their system and drive a motor vehicle or watercraft — they will be arrested.
Texas Penal Code 49.1(1) says that the alcohol concentration is defined as the number of grams of alcohol in your system per 100 ml of blood or 210 liters of breath. A breath test is an indirect test of BAC performed in the field or in a lab that provides immediate results. A legal blood alcohol test is performed on whole blood using gas chromatography.
Officers can require DWI blood testing if the driver refuses to take a breath test, if the driver is unconscious, or if they suspect any substance, including alcohol and drugs, intoxicated the driver. Blood testing is also mandatory if you are intoxicated and driving a vehicle with a minor passenger or you’ve been convicted before of two DWI charges or one DWI-related felony such as intoxication assault or intoxication manslaughter.
Other circumstances in which officers could require a blood test if the driver caused an accident that resulted in serious injury or death.
According to the regulations, someone can only take a blood sample in a sanitary place. They must be a qualified person, meaning a physician, technician, registered professional nurse, or licensed vocational nurse.
There is a caveat if you refuse a breath test — the officer must then obtain a DWI blood search warrant from a magistrate (not an officer of the peace or a municipal judge) and provide an affidavit that establishes sufficient probable cause, such as a failed field sobriety test. The officer must also show the evidence to be seized, in this case, a blood sample from the alleged offender.
What If Your Results Are Below 0.08?
You can still be arrested for DWI even if you pass the field sobriety test and your BAC is less than 0.08 if the officer believes beyond a reasonable doubt that:
- You have lost the reasonable use of your physical or mental capabilities
- You are impaired due to alcohol consumption
However, without a blood alcohol test, the court may be persuaded otherwise more easily.
Other DWI Blood Tests
Besides alcohol, your blood can be tested for other substances, including:
You can also be arrested for DWI due to the effects of over-the-counter and prescription medication. Blood testing can detect many of these substances as well. The gas chromatograph is the industry gold standard for identifying drugs and metabolites in your blood.
Did You Give Consent?
If you operate a motor vehicle or watercraft in a public place, you give assumed consent for any alcohol or drug testing. The implied consent law says if you are driving on the roadways of Texas, you have agreed to provide one or more chemical tests to measure your BAC.
If you refuse to provide the required sample, the authorities can automatically suspend your license and use the refusal against you if your case goes to court. These penalties may be applied even if you are acquitted of DWI.
The penalties elevate if you refuse on more than one occasion. Your license may be suspended for up to 180 days the first time you refuse. After that, you face a license suspension of up to two years.
All Is Not Lost
You may feel hemmed in by these statutes and requirements, but an experienced DWI attorney has ways to help you fight a DWI conviction based on a blood test.
Suppose a blood sample isn’t taken until hours after the DWI arrest. In that case, you can challenge the result by stipulating that it doesn’t prove you were intoxicated at the time you were stopped. Your BAC continues to rise for several hours after your last drink, implying the BAC could have been lower at the time of the arrest.
The prosecution may use Retrograde Extrapolation to “go back in time” and determine your BAC when you were stopped. Still, the prosecutor must have specific information to make the calculation accurate, information only you can give during your interview with the arresting officers.
You are required to provide your weight, the time of your last drink, and how long you had been drinking; that is all. However, other factors that change your blood alcohol level is how much you have eaten and when you ate last. Your attorney can challenge the entire process.
Blood Vial Challenge
The blood vial challenge is based on how the blood sample was taken and stored. Typically, it must be stored in a vial with an anticoagulant, preservative, and tamper-proof seal, and the test must be run on whole blood, not serum or plasma.
If a physician ordered the blood alcohol test instead of the police, the test is considered to be for medical purposes only and is not a “legal blood sample.”
Skin Cleaner Challenge
If the person drawing the blood sample uses a disinfectant that contains ethanol, some of the substance could make its way into the sample, contaminating it and falsely increasing the BAC.
The equipment used to draw the blood sample may not have been sterile or unadulterated. Suppose the qualified personnel who draws the blood has already prepped the exam room by opening and removing needles, syringes, and other paraphernalia before you arrive. In that case, the test result might not be acceptable.
What if the blood sample was neglected in the lab and left for several hours before testing? The sample begins to decompose, which elevates the alcohol concentration.
Chain of Custody Challenge
A chain of custody must accompany every legal blood sample as it moves from one person to another or into and out of storage. The chain of custody must show who handled the sample and where it was at all times.
Any gap in the chain of custody can be used to question the validity and accuracy of the sample and test results.
Your attorney can also question whether the officer had probable cause to stop you in the first place. If the officer required a warrantless blood test after you refused a breath test and there were no exceptions allowing it, the test result could be suppressed in court. Did the officer give you a Miranda warning? If not, then any blood test is inappropriate.
Why You Need a DWI Attorney
DWI law in Texas is convoluted and full of exceptions. An experienced attorney knows how to uncover any discrepancies in the arrest, how the blood sample was obtained, and how the sample was treated and stored.
A DWI is a serious conviction that could keep you from certain jobs and make it difficult to find shelter. Call the office of Brett Podolsky if you have been arrested on a DWI charge. He will fight for your rights.