In the State of Texas, the legal standard for alcohol intoxication is having a BAC (blood alcohol concentration) of .08 or higher. Either your blood or breath sample concentration is measured against 100 milliliters of your blood.

A blood test is harder to fight in court, so it is the last thing you want to happen when arrested for DWI. This test is unpleasant and invasive, but to contest having it performed does take a bit of legal footwork. If you have any questions regarding a DWI blood test, contact the Fort Worth DWI Defense Lawyer today.

How DWI Blood Testing is Measured in Texas

BAC (blood alcohol concentration) can be measured through either a breath or blood test. Texas Penal Code 49.01(1) alcohol concentration is the number of grams of alcohol in your system per:

  • Sixty-seven milliliters of your urine
  • One-hundred milliliter of your blood
  • Two-hundred ten liters of your breath

A blood test will measure your blood alcohol concentration directly. A breath or urine test will provide indirect measurements. Any one of these three tests can be administered at the discretion of the arresting officer in lieu of or in addition to field sobriety tests. The officer will decide which tests to offer. Any one of these tests showing results of a BAC at .08 or higher means you are legally intoxicated, and you will be arrested for DWI.

Even should you pass these tests, or your BAC is less than .08, you can still be arrested. If the officer believes beyond a reasonable doubt you have lost reasonable use of your physical or mental capabilities, or you are impaired due to alcohol consumption, they can arrest you.

The method in which blood is tested in Texas is by use of gas chromatography. This device provides a direct measurement of blood alcohol concentration. Of the three tests, urine, breath, or blood, the blood test tends to be the more accurate measurement.

Do You Have to Consent to Blood Sample When Arrested for DWI?

You have a constitutional right to refuse to have a blood test taken when arrested for DWI. Refusing this test; however, gives the authorities the right to suspend your license automatically, and use the refusal against you should your case lead to prosecution. Refusing may only buy a little time on your part, as police can now obtain a warrant that will force you to provide the sample. These warrants can be requested at any time, and any day so even if arrested over a weekend or holiday, it is not going to delay the authorization being delivered.

Procedures for Testing Blood Alcohol when Charged with DWI

If a Texas police officer has reasonable concerns that you are driving a vehicle intoxicated, Implied Consent Law allows them to request a breath or blood test to check your BAC. If the officer suspects drinking has been involved and you are operating a motorized vehicle, it is their sole discretion to determine whether or not either of these tests will be administered.

  • Implied Consent Law

The Implied Consent Law states that if you are driving on the roadways of Texas, you have agreed to provide one or more chemical tests to measure your BAC (blood alcohol content).

If you should refuse to give a sample of either blood or breath voluntarily, you can face additional administrative consequences or penalties along with the standard DWI sentencing. The penalties are still allowed to be applied to you even should you be acquitted of DWI charges.

Refusing blood testing does not mean you will not have to provide a sample. The officer can obtain a warrant which will force you to complete the blood test even if you refuse to do it voluntarily.

If you refuse the test, there will be consequences:

  • The first time you refuse to provide a blood or breath test voluntarily, your license is suspended for up to 180 days.
  • The second time you make the refusal, your license is suspended for up to two years.
  • The third time you refuse to take these tests, your license is suspended for up to two years.

When refusing these tests, the officer should advise you that your refusal can be used against you in a court of law. The officer should also notify you of the suspension of your driving privileges.

There are situations where a law enforcement officer can rely on the Implied Consent Law to draw your blood. These situations include you not being conscious at the scene or other reasons where they cannot withdraw your consent.

Can I Choose a Breath or DWI Blood Test?

In Texas, it is the arresting officer’s choice on whether to ask for a blood or breath test. Under the Texas Transportation Code, if the officer has reasonable grounds to believe you are DWI, they can request one or more samples of your blood or breath.

Once the officer decides which tests to perform, you can either submit or refuse. The officer will then have to advise you of your rights if you refuse and the possible consequences. If you do not resist, the testing should be completed as soon as possible.

Is DWI Blood Testing Mandatory?

You have a constitutional right to refuse to provide DWI blood testing. However; there is a situation where a police officer has the right to take the sample against your will. Texas law allows for arresting officers to obtain a warrant in cases where drivers refuse to complete a chemical test when:

  • The officer presents an affidavit detailing their suspicions and what they are based on to a judge. The judge will then issue a warrant where you will have no choice other than to provide a sample.

If the officer proceeds with taking your blood sample without obtaining a warrant after you’ve refused to provide one,  your Fort Worth DWI Defense Lawyer will be able to have the results excluded from your DWI trial.

A search warrant that will authorize law enforcement to force you to provide a blood sample for DWI blood testing is an evidentiary search warrant under Texas Code of Criminal Procedures Article 18.02(10). This rule states that an officer must carefully follow specific requirements:

  • The blood search warrant has to be signed by a magistrate. It cannot just be a Justice of the Peace, or municipal court judge.
  • The warrant must be accompanied by an affidavit sufficiently establishing probable cause showing you committed DWI
  • The evidence sought to be taken would constitute evidence needed for the DWI

Under the laws in Texas, an officer can compel or force you to give a sample of blood if they have reasonable grounds to think:

  • You were intoxicated while operating a watercraft or a motor vehicle in a public place
  • You violated Alcoholic Beverage Code Section 106.041
    • Section 106.041 is in reference to a minor who has any amount of alcohol in their system while operating a watercraft or motor vehicle in a public place.

Another situation that allows for the drawing of your blood without consent is if you are arrested for DWI, which involves an accident. If the accident causes a passenger or driver of the car you’ve hit to be taken away in an ambulance due to injuries, Texas law permits police officers to take a blood sample from you forcibly.

Police can also forcibly take a blood sample without your consent if:

  • A person dies or has died from the injuries sustained in the accident
  • Another person, other than you, has serious bodily injury
  • You were driving a vehicle with a passenger younger than fifteen years of age at the time they arrest you for DWI
  • You have a record or previous felony DWI conviction
  • You have a record of previously being convicted of intoxication manslaughter
  • You have a record of previously being convicted of intoxication assault

Can I Choose Where My DWI Blood Testing is Performed?

Most law enforcement officials will not tell you, but you are able to have a breath or blood test performed by your healthcare professional. You can choose your regular doctor or one of your choosing under Texas Transportation Code Section 724.09.

  • Texas Penal Code 724.09

Any person submitting to a sample of blood, breath, urine, or other bodily substance when requested by an officer of the law, can within a reasonable time ask a physician, qualified technician, registered professional nurse, or chemist of their choice to analyze the second sample of said substance.

If this is your choice, the police are required to give you a reasonable opportunity to contact a healthcare professional of your choosing to take an additional sample. This Penal Code only applies to blood testing; it does not cover breath tests. The officers are also not responsible for transporting you to a facility for second testing. You may have to request the healthcare professionals come to the station to perform the sample draw.

Should I Provide Breath or Blood DWI Testing?

The breath or blood DWI testing methods both have their accuracy issues. Blood tests are generally more accurate; however, there are many factors that can render them entirely inaccurate. Your Fort Worth DWI Defense Lawyer may conduct an investigation into the collection and testing of your sample, which could uncover evidence that your test results were tainted. If this is discovered, your test results would be excluded from your trial. These are a few examples of how DWI blood testing could be affected:

  • Storage and Collection

There are several ways faulty collection, or improper storage practices can cause a BAC result to be unreliable:

In some cases, samples are not taken for hours after an arrest. As time goes on after your arrest, your BAC can rise or fall depending on when you had your last drink. If law officials wait to take your sample, it is possible your BAC at the time of the test was higher than when you were driving.

Not properly storing or taking the sample can ruin its integrity. Mistakes in drawing the blood can also taint your entire specimen. The risk of contaminating your sample is much higher if it is not stored correctly. Chemicals added to the blood sample to prevent it from fermentation creates alcohol. So, if your sample was not stored correctly, it may leave a false positive on your test results.

  • Custody Chain

When your blood sample is taken, it must be analyzed in a laboratory setting. This means there are several hands it will travel through on its way to the lab for the testing process. The State has to be able to account for each person that handled your sample, and there cannot be a link in this custody chain that is unaccountable. Your Fort Worth DWI Defense Lawyer will require the results of this blood test, along with the accountable custody chain. If the State cannot provide adequate proof, your sample was handled according to the law; the test results can be excluded from your trial.

  • Issues with the Breath Test

The DWI blood testing has problems that can make it unacceptable to use as evidence against you at trial, but the breath test has even more. The machine used for taking your sample can contaminate your specimen. If the machine is not correctly calibrated, or an individual without proper training conducted the test, the readings are inadmissible. Your test could also have false positive reading because of the food you’ve recently eaten.

If a breathalyzer machine is not properly calibrated, the results it puts out are not worth the paper they are printed on. These machines are extremely sensitive. They can only provide accurate readings if they are maintained carefully. If not, they cannot offer correct readings or results.

Even if the police have correctly maintained and calibrated their equipment, there are still other factors that can skew the results. Before even applying the breathalyzer test, the officer has to be properly trained on how to operate it. Your Fort Worth DWI Defense Lawyer may be able to exclude the results if it is proven the officer did not complete the proper training before giving you the breath test.

Other factors can render the readings inadmissible such as foods you may have eaten. Many different foods will lead to false BAC results, including:

  • Sugarfree gum
  • Over-ripe fruit
  • Energy drinks
  • Yeast bread
  • Lip balm
  • Honeybuns
  • Vinegar
  • Hot sauce
  • Kombucha
  • Vanilla extract

Other issues can also affect inaccurate breath test results, such as medical conditions. Asthma, diabetes, and acid reflux can affect a breath test and cause the results to report a false positive reading. Other factors such as insufficient breath samples, unusual breathing patterns as well as shallow breathing can cause a breath sample to show alcohol when you haven’t even been drinking.

Urine Test for DWI in Texas

Another test which some officers may request if you are suspected of being intoxicated is a urine test. This test is the least accurate form of testing BAC, and it is rarely requested. The urine test is better used for testing for illegal drug use.

The reason a urine test is unreliable is the percent of alcohol in a person’s urine can fluctuate a lot depending on their bladder function. This bladder function does not directly correlate with blood alcohol content in your urine. Studies have proven that the alcohol level in urine is more than 1.33 times the amount of alcohol levels found in a person’s blood. Along with these discrepancies, urine samples can also be contaminated by errors in the lab.

How will the DWI Blood Testing Affect DWI Case in Texas?

Texas courts have stated that a DWI blood test is relevant in the issue of intoxication. What is important to remember; however, is a blood test does not prove you were intoxicated at the time you were driving. The prosecution has to prove beyond a doubt you were intoxicated at the time you were operating the vehicle.

If a blood test sample was taken several hours after your DWI arrest, it does not provide specific conclusions as to your intoxication level when the officer stopped you for suspicion of DWI. The prosecution is going to attempt Retrograde Extrapolation as a way of going-back-in-time to determine your BAC at the time you were stopped.

  • Retrograde Extrapolation

Retrograde extrapolation is a mathematical and scientific method used by toxicologists and chemists to estimate what a person’s blood alcohol concentration was at a certain time. It is based on test results obtained at a later period of time.

For the prosecution to complete the necessary computations for retrograde extrapolation, they have to have certain information only you could have given during your interview with the arresting officers. The minimum amount of information you would have had to provide under Texas law includes:

  • Your weight
  • At what time you had your last drink
  • How long of a time period had you been drinking

Other factors affect retrograde extrapolation in addition to this information, which includes how much you have eaten, and when you last ate food.

Defense Against DWI Blood Testing Results

There are solid defense strategies against Texas DWI charges. These strategies are used even if the police have a DWI blood test showing your BAC was over the legal limit. Proving a bad blood test is one way to discredit the State’s evidence against you, so a drunk driving charge is not on your record. There are several ways to defend this charge and your Fort Worth DWI Defense Lawyer will work with to protect your record and your future.

BAC tests are like any other forensic evidence, which means they are not immune to challenge on a variety of levels. These are a few of the defense strategies your Fort Worth DWI Defense Lawyer can use as scientific challenges to your DWI blood testing results:

  • Blood Sample Defense

A sample of blood is typically drawn for alcohol testing in one of two DWI situations- it was requested by the arresting officer who suspects DWI, or by a hospital medical professional in connection with treatment and diagnosis of one brought into the hospital after an accident.

Blood drawn at the request of the officer is considered ‘legal blood’ which indicates whole blood has been collected. At the hospital, when a blood sample is taken, it is considered ‘medical blood’ and is typically serum. The differences in how the specimen was collected, prepared, and tracked between the ‘legal blood’ and the ‘medical blood’ provide a strong argument for lack of trustworthiness as forensic evidence.

When challenging the admissibility of ‘legal’ blood samples into evidence, your attorney can question several factors, including whether or not the medical professional drew and tested the sample under compliance with state regulations.

  • Blood Sample Storage

State regulations specify vials used to collect blood samples have to contain a preservative and anticoagulant and must be sealed or capped to prevent evaporation. These seals should be tamper-proof, and in some jurisdictions, they must be marked with essential tracking information.

The vials used for legal samples are required to contain the preservative and anticoagulant and should have a gray-colored septum to indicate the chemicals are inside the tube. Other vials used for medical or lab purposes will have different colored seals such as purple, yellow, or red to signify whether or not they contain chemicals.

Medical blood samples may not have preservatives or anticoagulants in them and are typically sealed with a red septum to show the blood sample is pure blood without chemicals. Blood in a red-topped vial will become clotted and deteriorate much faster than those with gray tops as they lack preservatives.

Your Fort Worth DWI Defense Lawyer can ascertain the condition of the tube used for your DWI blood sample. If the tube, or vial, is improperly capped or filled, it will affect the BAC value. If a red-sealed vial was used for your sample, and it was sent to an outside lab for testing, it had to have been continuously refrigerated. The alcohol content in this sample could have increased if the vial was left at room temp. If this blood sample was not handled properly, your lawyer could have this evidence deemed inadmissible.

Find a Lawyer Near Me to Fight DWI Blood Testing Results

There are many ways to argue the results of DWI blood testing. Call the Fort Worth DWI Defense Lawyer to help build a defense that will protect your future and your rights. Understand that blood tests are not infallible, and with an experienced defense, you could have these charges dismissed or reduced. Call today at 817-470-2128, and we will begin building your defense against the DWI charges.