Free Consultation713.864.9000

Aggressive Trial Attorneys

Super Lawyers
Lawyer Scientist
Avvo Rating
AV Preeminent

Notable Victories

not guilty


Galveston No. 1


Attorney: Mark Thiessen

0.161 BLOOD TEST!!! Client came down from Dallas for the weekend. Checked into his AirBnB and then headed for the Strand. Didn’t know that it was Biker Weekend in Galveston and the Strand was packed. The client left about 11pm and was pulled over by UTMB police for failing to signal a lane change on Broadway. However, the video also showed the police officer doing the exact same thing. Client admitted to drinking and was wearing a “Fuck It, Let’s Drink” shirt. Officer called in a DWI officer and had client step out for the SFSTs. The officer performed the HGN while the client was facing many cars passing in close proximity. But of course, she said he exhibited 6 out of 6 clues (they always say that). The client then performed the Walk and Turn and looked great. Only barely failing the test according to the officer’s own clues. The client then passed the One Leg Stand. Client requested a lawyer when asked for blood and they got a warrant. Blood came out of Harris County DPS with Rachel Aubel testifying. Of course Ms. Aubel testified that she didn’t make any mistakes and her work was performed accurately. She even gave herself 100% in never mixing up a sample in 5 years and 10s of thousands of vials.

Amanda Culbertson, our toxicologist, was able to show how they routinely violated their SOPs and their standards were out of tolerance. The overzealous DAs tried very hard to keep Ms. Culbertson off the stand or prohibit her testimony, but the Judge saw through their antics and let the jury hear the whole truth. Of course, Ms. Aubel rebutted that everything was still perfect even after we exposed all the problems with their lab. This I why we need independent labs! NASA makes mistakes, but police/government labs won’t ever admit anything is wrong. The jury ultimately threw out the blood test and simply said the client didn’t’ look anywhere close to twice the legal limit. Something had to be wrong, it just didn’t add up. They also noted how he could look great on all the tests we could see with our own eyes, but fail the HGN with every clue. Didn’t add up. Thank you to the jury for standing up for the People of Galveston County and demanding better forensic science. Thank you for giving my client his freedom back after 18 long months.

View all
Mark Thiessen


DWI, Criminal & Civil Trial Defense Attorney

“I'm a trial-tested Super Lawyer focused on fighting for my client's freedom. If you hire our firm, we're available 24/7, because, at the end of the day, we work for you.”

What to expect?

Thiessen Law Firm. Well-known for both award winning Houston DWI Lawyers and aggressive trial-tested criminal defense techniques, we fight like no other, for your DWI case. Our trial attorneys not only fight for positive results, we also care deeply about the overall well-being of our clients.

Why choose thiessen law?

  • Aggressive Defense Attorney
  • Dedicated Team to Fight for You
  • Free Case Evaluation
  • No Hourly Rates
  • 24/7 Accessibility
Continue Reading

Trial attorneys that fight for you in Houston and all Texas counties

Our Houston DWI Attorneys always fight our hardest. We tell the truth about your DWI or DUI case, and facts take precedence over promises. We hold honesty and virtue in highest regard and it is the foundation of ensuring your DWI or criminal case ends with a satisfying, positive outcome.

When you get a DWI, DUI or other criminal charge in Harris County, your life is changed, no matter the verdict. At Thiessen Law Firm, you will be represented by a Houston DWI lawyer who will ensure you’re able to continue on with the life you want. You’ll never feel forced into taking a deal that you don’t want, or accepting terms you don’t fully understand. Mark Thiessen is recognized as an ACS CHAL Lawyer-Scientist for his efforts to understand the science and technology behind DWI testing. This investment in his education and training provides clients with the knowledge needed to fight for their rights effectively and fairly.



Not Guilty

View More →


Client Satisfaction

View More →


Speaking Events

View More →



View More →

Free eBook

A Texas DWI can cost you $15,000

Get the DWI facts no Texan should drive without, including:

  • 3 rights you can exercise when you get pulled over
  • How to save your license from suspension
  • Why you should refuse any roadside tests
  • What to say during your booking
Not a valid email
A Citizens Guide to beating a DWI in Texas

Latest News

People Are Reading

You have 15 days to save your driver's license

Act fast if you've been charged with DWI or DUI in Texas. Here’s something you might not see from other Houston DWI Lawyer websites: If you've been arrested for a DWI or DUI in the state of Texas, you are facing two cases against you. The first one is the criminal case by the state of Texas, and the other is by the Texas Department of Public Safety to suspend your license.

License Suspension

In The Media

In The Media

Jurors find woman not guilty of intoxication manslaughter in fatal West Lubbock crash

The defense attorney for a 23-year-old woman said a flawed Lubbock police crash investigation provided enough reasonable doubt for a 12-member jury to find his client not guilty in a fatal 2014 West Lubbock wreck.

Read the full story

Speaking Engagements

As Houston’s DWI Super Lawyer, Mark Thiessen has consistently set high standards in his field since establishing his firm. His scientific investigation process & comprehensive list of victories has brought him to the forefront of national recognition as he is sought by industry leaders & legal organizations to deliver trial strategy seminars.

Austin, TX

State Bar of Texas

Handling Your First (or Next) DWI Case: Handling Breath/Blood Test Analysts

Register Now
Philadelphia, PA

DUIDLA Fall Seminar 2018

Not Guilty v. Cerberus; Beating Intoxicated Manslaughter Cases

Houston, TX

TCDLA Top Gun DWI Seminar

Top 10 DWI Trial Tactics to Shooting Down the State’s Case

Happy Clients

The BEST Attorney in Harris County and Probably One of the Best in the Nation

Mark Thiessen is by far the BEST attorney in Harris County and probably one of the best in the nation. His firm is extremely polite and professional. Mark and his staff were always there for me when I had questions or concerns. He was able to get my DWI dismissed in Harris County which is a huge relief. I would highly recommend Mark for any DWI or drug related case.


DWI client

Fantastic Lawyer

I would HIGHLY recommend hiring Mark Thiessen as your attorney for any criminal case that you have received in the Harris County area. He is extremely knowledgeable of the court system and what actions can be taken pre-trial in order to have the best outcome at your court date. I was put on probation for a DWI a year previous to hiring Mark as my attorney. I failed to complete the requirements in order to get off of probation. My probation was revoked and sent back to the courts. That’s when I hired Mark. He told me to go complete the rest of the requirements for probation and get myself a court date. When we got to court he persuaded the judge not only to dismiss my probation, but dismiss it successfully. In court he made small talk with the judge and prosecutor which told me that he knew them and had a good relationship with them. Which was not the case for other attorneys that went in front of this judge. Again you can’t go wrong hiring Mark. He is great attorney and great person.


DWI Client

If You Want a GREAT Lawyer, Mark Thiessen is Your Man

I found Mark Thiessen through several of my friends. I was having serious issues with the lawyer I had at the time. He kept telling me I was going to jail when I had done nothing. He did not believe me, and I believe he was gonna have me put in jail and not fight for my innocence. From the moment I met Mark Thiessen, I knew he was going to do everything for me to keep me from that horrid jail. I was not allowed to leave my county. He drove all the way up to The Woodlands to meet me at Starbucks to speak on my case. He got all the charges against me dropped within minutes. He’s truly the best lawyer. He has a lot of respect from his piers including the judge that actually told me I was very lucky to have such a great lawyer. And trust me, I know I was lucky to have found him, and that is the gods honest truth. If you want a GREAT lawyer, Mark Thiessen is your man.


DWI Client

The Best Lawyer in the Industry

I chose Mark Thiessen to represent me in a DUI / DWI case and it was the best selection/decision that I could have made. I found out about Mark through Internet search and reached out to him and his office. Upon meeting with Mark – I immediately knew that he was the right lawyer/attorney to represent me and give me the best opportunity to win my case. Mark is an expert attorney with a work ethic that is second to none. He is always available. He is a master of his craft and will give you the best opportunity to win your case. He will be prepared and he will do everything to ensure your case is won. He will actually be more knowledgable on the aspects of law, facts of the case, than the individuals that have accused you of your offense. He was highly successful in my case, even despite some of the alleged facts not being in my favor. We won the case and all charges were dropped. Thanks Mark!


DWI Client

Free Consultation

Missing name
Not a valid email
Not a valid phone
aggressive defense