What is a chemical test for DUI and DWI? Driving under the influence of drugs or alcohol (DUI) and driving while intoxicated (DWI) are both considered misdemeanors under Texas law. If you are suspected of either of these actions, a member of law enforcement will likely administer a chemical test to detect alcohol or substances in your system at that point in time. 

If you’re curious about what is a chemical test for DUI and DWI, Mark Thiessen, a top DUI defense attorney in Houston, is here to answer your questions regarding the chemical tests used by law enforcement in DUI/DWI cases.

What are the 3 chemical tests used to test for alcohol/drugs?

So, you’re pulled over by a cop for suspicion of driving under the influence. How are they going to prove it? Chemical tests in Texas are typically done in three ways –– a breath test, a blood test, or a urine test –– and are used to show that the driver’s blood alcohol concentration (BAC) is 0.08% or higher showing the presence of drugs and/or alcohol in the body. These tests allow the cop to see if you should be arrested and charged with a DUI/DWI. Here’s how they work.

Breath Analysis

A breath test using a machine called a Breathalyzer is usually given at traffic stops and is potentially the most common form of alcohol testing in DWI cases. To take a Breathalyzer test, you simply blow into the machine and it will calculate the amount of alcohol in your breath through a percentage to determine the amount of alcohol in your blood. Though not quite as accurate as a blood test, breath tests are the easiest for cops to perform at traffic stops. 

So, what happens if you refuse to take a Breathalyzer test in Texas? When you are pulled over by a policeman, they will ask you to take a breathalyzer test if they suspect you are drunk. Let’s be clear –– you do not have to consent to a breathalyzer test, but you will face consequences if you refuse to submit to chemical testing. You do have the right to refuse to blow into the Breathalyzer, however, a warrant for a blood test can be issued easily and quickly and if the warrant is granted, they are legally allowed to take your blood. At this point, further refusal will result in further consequences. 

This is why we always say, “Blow, Don’t Bleed.” 

Blood Test

As mentioned above, the legal standard for intoxication in Texas is a .08% blood alcohol concentration (BAC), which can be measured by a breath or blood test. While breath tests are more common, they are far less accurate than a blood test. To measure how much alcohol is in your blood, they will take 100 milliliters of blood from you and put that blood sample through the process of gas chromatography to determine whether your BAC is over the legal limit. 

Can you refuse a blood test? Technically yes, but we do not recommend this. Refusing a blood test can allow the state to suspend your license and use your refusal as evidence in future prosecutions against you. And, it’s very likely that they will get a warrant for a blood test to make you submit to chemical testing. Believe us, it’s better to just take the blood test if asked.

Submitting to a DWI blood test is the last thing you want to happen. Not only is the test invasive and unpleasant, but it’s also much harder to fight in court. Both blood and breath tests have their fair share of flaws, but contesting a blood test requires more footwork and expertise, making the results more believable to a jury.

Urine Test

A urine test, also called urinalysis, is only used in chemical testing if the cop suspects the driver is under the influence of drugs or other controlled substances. However, urine tests are generally viewed as being the least reliable of the three major chemical tests used in DWI cases. 

Here’s an example of why: a driver is pulled over on suspicion of driving under the influence of drugs, and after taking a urine test, the driver’s sample detects the presence of an illegal drug. However, because drugs tend to stay in a person’s system much longer than say alcohol does, a urine test cannot prove that the person was currently driving under the influence. That driver could be sober at the time of the test. 

Again, you are legally allowed to refuse to submit to chemical testing, but there are consequences to doing so.

The problems with DWI chemical tests

It’s no secret that BAC tests don’t always yield the correct results. Some medications, health conditions, and other factors can make your BAC seem higher than it really is when tested. In some situations, inaccurate results from breathalyzers or blood testing can lead to people being convicted of a crime they never committed. If the State has a breath or blood test, your case might become more difficult to fight, and could result in an unfair conviction if you don’t have the right legal representation on your side.

Having this type of conviction on your record, regardless of whether it’s your first DWI in Texas, can be life-altering. You do not want to face even the most minor DWI Texas penalties. If you are charged with a DUI/DWI, you need an aggressive, experienced DWI defense attorney who knows how to fight a DWI to get you a favorable outcome. You need Mark Thiessen.

Charged with a DWI from Chemical Testing Results? Hire Thiessen Law Firm ASAP for Aggressive Defense!

Now that we have covered what is a chemical test for DWI, it’s important to know that in terms of chemical tests, blood is more difficult to defend than breath. The truth is, few DWI defense attorneys understand the science –– and even fewer district attorneys understand blood testing results. It is absolutely crucial that you hire a DWI trial attorney such as Mark Thiessen who has the know-how to fight breath or blood tests. 

As a certified Forensic Lawyer-Scientist by the American Chemistry Society and the Chemistry and the Law Division, Mark Thiessen has mastered the science behind intoxication analysis and has used this knowledge to successfully fight both blood and breath tests in court.

If you find yourself on the wrong end of a breath test, do not say anything that could incriminate you, and contact Mark Thiessen ASAP at 713-864-9000 or fill out our online contact form to schedule a free consultation today. Your future freedoms may depend on it.

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Mark Thiessen is an aggressive trial lawyer best known for his devotion to justice for his clients and high rank as a DWI Super Lawyer in Texas.