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Mark R. Thiessen

Fighting for the People and Winning.

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

Phone: 713-864-9000

Website: thetexastrialattorney.com

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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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NCDD Journal

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FROM OUR BLOG

Interview With an Amicus

06/27/2025

Written by Michelle L. Behan Amicus Curiae (Latin for "Friend of the Court") refers to a brief that is filed by an interested, non-party to the matter under consideration. This is often done in cases where organizations and entities wish to provide the reviewing court with their point of view, be it social or public policy implications, or special interest agendas....

Keeping FSTs Out of a Trial

04/23/2025

Written by Neil Halttunen I want to address a common issue that DWI practitioners are facing, trying to keep FSTs out of a trial. One way is to take the position that FSTs are scientific evidence and make the prosecutor lay scientific foundation which they rarely can do. The HGN test was the result of several studies. See Generally Session 8 of...

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