About Guy
Guy Thiessen earned a B.S. in Finance and Insurance from Oklahoma State University in 1983 and a J.D. from Oklahoma City University School of Law in 1989. He moved from classroom to courtroom at a time when the legal landscape in Oklahoma was shifting. His education provided a practical grounding in both business and law.
He joined the American Association for Justice in 1989 and has been active in its Nursing Home Litigation Group. That membership signals a long-term engagement with cases involving care facilities. He also became involved with the Oklahoma Association for Justice, joining its board in 1996 and serving as president for the 2008009 term. Those roles placed him in the middle of statewide discussions on civil justice and trial practice standards.
Thiessen is admitted to practice in Oklahoma and Arkansas, and he holds admission to the 10th and 8th U.S. Circuit Courts of Appeal and the U.S. Supreme Court. Those credentials reflect both trial and appellate capability. Over the years he has maintained those admissions while handling matters that cross state lines and that sometimes proceed to higher courts.
His work has included cases arising out of care at long-term facilities. Membership in the American Association for Justice Nursing Home Litigation Group suggests experience in the medical-legal issues those cases present. He also handles other civil litigation matters that draw on his background in finance and insurance. That combination allows him to address disputes where business and personal injury overlap.
Colleagues and clients have known him through his leadership in professional organizations. Serving on the Oklahoma Association for Justice board since the mid-1990s and later as its president gave him exposure to court reform debates and continuing legal education efforts. He has remained active in those circles while carrying a private practice load.
Thiessen maintains an office under the GT Law Office name at Sixth and Boulder. The office is described as offering free parking and serving local clients in the downtown area. From that base he continues to accept cases in state and federal forums for which he is admitted.
As of 2026 he practices under the GT Law Office name and remains engaged in civil litigation, including matters involving nursing home care and related insurance and finance issues.
