Mark Thiessen

Mark Thiessen is a highly recognized DWI and criminal defense attorney who focuses on aggressive trial advocacy. He represents clients facing serious criminal charges and refuses to settle cases when justice requires a full trial. His practice centers on defending complex DWI, drug, assault, and intoxication manslaughter cases while protecting constitutional rights and demanding accountability from prosecutors through skilled courtroom litigation in high-stakes criminal proceedings across Texas courts statewide.

Mark earned a B.B.A. in Marketing from Texas Christian University and a J.D. from South Texas College of Law. His legal education included advanced training in criminal law and trial advocacy. He also completed international legal studies focused on criminal justice, forensic science, and evidence analysis, strengthening his ability to analyze scientific issues that often determine outcomes in complex DWI and criminal cases handled by modern courts today nationwide.

Throughout his career, Mark has tried numerous high-level criminal cases and secured dismissals, acquittals, and reduced charges for clients. He is board-certified in Criminal Law and multiple DUI defense disciplines, reflecting exceptional trial skill. His forensic knowledge allows him to challenge police methods, testing procedures, and unreliable evidence, helping clients avoid severe penalties and long term consequences arising from complex criminal investigations and courtroom litigation, as well as daily practice demands.

Mark Thiessen also serves as a legal educator and leader within the criminal defense community. He regularly teaches attorneys, judges, and law enforcement about forensic science and trial strategy. Through litigation, education, and advocacy, he helps protect due process, promotes fair enforcement of the law, and ensures individuals accused of crimes receive knowledgeable representation at every stage of the legal process from investigation through trial and appeal when justice requires action.

Law Office Affiliations

• Attorney, Thiessen Law Firm
• Member, State Bar of Texas
• Member, Colorado Bar Association
• Member, National College for DUI
• Member, American Bar Association
• Co-chair, Texas Criminal Defense Lawyers Association (TCDLA)
• President, Harris County Criminal Lawyers Association
• Former President, DUI Defense Lawyers Association (DUIDLA)

Licensed State

• Texas
• Colorado

Education

• South Texas College of Law (STCL)
  Juris Doctor (JD)
• Texas Christian University
  BBA in Marketing

Awards & Badges