Mark R. Thiessen

Mark R. Thiessen

Fighting for the People and Winning.

733 E. 12th 1/2 Street
Houston, TX 77008

Phone: 713-864-9000


Board Certified General Member

About Mark R. Thiessen

Mark Thiessen is a criminal trial lawyer and the Chairman/CEO of the Thiessen Law Firm in Houston, Texas. Mark is Board Certified in (1) Criminal Law by the Texas Board of Legal Specialization 2018; (2) DUI Law by the DUI Defense Lawyers Association 2018; and (3) DUI Defense Law by the National College for DUI Defense through the American Bar Association 2020. Mark earned the American Chemical Society-Chemistry and the Law (ACS-CHAL) Forensic Lawyer-Scientist designation, which is the highest form of scientific recognition available for lawyers. Mark is a frequent legal seminar lecturer, author of numerous published legal articles, and a faculty member for various organizations. Mark is the current DWI Committee co-chair and on the Board of Directors for Texas Criminal Defense Lawyers Association (TCDLA), 2020-21 President of Harris County Criminal Lawyers Association (HCCLA) and a Charter Member and Parlimentarian for DUI Defense Lawyers Association (DUIDLA). Mark is a 9 time Texas Super Lawyer and in the Top 100 Super Lawyers in Houston (2017-21). From 2019-21, Mark was the only DWI lawyer to be named to the Top 100 Super Lawyers in all of Texas. Mark has won DWI trials from total refusals up to quadruple intoxication manslaughter.

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Horizontal Gaze Nystagmus Test


By Andy Sotiropoulos ( The Horizontal Gaze Nystagmus test, commonly referred to as HGN, is in this authors opinion the most discussed and debated field sobriety test of NHTSA's Standardized battery of exercises designed to measure alcohol related driving impairment and/or blood alcohol concentration (BAC). It is the exercise which has been scientifically validated as most accurate by NHTSA and requires...

Discovery Requests in Drug Recognition Expert Cases


By Neil Halttunen In order to be successful in a case involving a Drug Recognition Expert (DRE), you must gather the same materials that were used when the state to constructed their case. Use those same materials to deconstruct and get good results for your client. A lot of materials go into a DRE case; your mastery of those materials will...

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