How It Works

Texas law enforcement uses Intoxilyzer 9000 machines to administer breath tests. These devices analyze a deep lung air sample and estimate the amount of alcohol in the bloodstream.

When It’s Used

Breath tests are typically administered at the police station after arrest. While some portable breath tests (PBTs) may be offered at the roadside, only the results from station-based breathalyzers are admissible in court.

Legal Implications

If your BAC is 0.08% or higher, the state may use that as evidence of per se intoxication. However, if your BAC is below that threshold, you can still be charged with DWI if the officer believes you lacked normal use of your faculties.

How It Works

A blood test measures your exact BAC (or presence of drugs) through a laboratory analysis. Blood is drawn by a licensed medical professional, often at a hospital or jail facility, and sent to a DPS-certified lab for testing.

When Blood Tests Are Used

Blood tests are typically used when:

• A breath test is refused
• The DWI involves serious injury or death
• Drug impairment is suspected
• A search warrant is obtained for a blood draw

Legal Requirements

Blood draws must follow strict procedural guidelines. Failure to follow proper protocols can lead to suppression of the test results in court.

Refusing a Breath or Blood Test

Texas is an implied consent state. That means when you drive on Texas roads, you are deemed to have consented to chemical testing if lawfully arrested for DWI.

However, you can refuse to take a breath or blood test. But doing so comes with consequences:

• Automatic license suspension through the ALR (Administrative License Revocation) process
• Use of your refusal as evidence of guilt in court
• Possible search warrant for a mandatory blood draw

Refusal does not mean you’re safe from prosecution. It simply shifts the strategy of the case.

Challenging Breath and Blood Test Results

At Griffin, Cain & Herbig, we know that no chemical test is flawless. There are multiple ways to challenge the validity of breath and blood evidence.

1. Improper Administration

Breathalyzer tests must be administered by certified officers using properly calibrated machines. If the device was out of date, not maintained, or misused, the results may be unreliable.

2. Medical or Biological Factors

Certain medical conditions, such as GERD, diabetes, or low-carb diets, can affect BAC readings. For example, acetone in the breath of a diabetic person can be misread as ethanol by a breathalyzer.

3. Contamination or Mishandling of Blood Samples

Blood samples must be drawn, stored, and tested under precise conditions. If there is any contamination, fermentation, or chain-of-custody issue, the results may be challenged or excluded.

4. Unjustified or Defective Warrants

If a warrant was used to obtain a blood sample, we examine whether it was issued lawfully and based on sufficient probable cause. Any defect in the warrant process can lead to suppression of the evidence.

5. Margin of Error and Rising BAC Defense

Chemical tests are not exact. Most breath and blood testing devices have a margin of error of ±0.01% or more. If your test result was just over 0.08%, we may argue that you were under the limit while driving, and your BAC rose while waiting for the test.

Texas Law on Drug Testing in DWI Cases

Breath tests detect alcohol, but not drugs. If drug impairment is suspected, a blood test will be used to detect the presence of:

• Marijuana
• Prescription medications (like Ambien, Xanax, or painkillers)
• Illegal drugs (such as cocaine or methamphetamine)

However, simply having a drug in your system does not prove impairment. We work to show that the presence of a substance did not affect your ability to drive safely.

Consequences of Failing a Chemical Test

If your breath or blood test shows a BAC over the legal limit, or any measurable amount of drugs, the prosecution will likely rely heavily on that evidence. But remember, a test failure does not automatically mean conviction.

Penalties for a DWI conviction in Texas may include:

• Fines ranging from $2,000 to $10,000
• Jail or prison time
• Driver’s license suspension
• Annual surcharges to retain your license
• Probation
• Ignition interlock device
• A permanent criminal record

Challenging the test results can be a vital step in avoiding these outcomes.