The Texas Supreme Court has consistently described mandamus as “both an extraordinary remedy and a discretionary one.” To obtain mandamus relief respecting an action of a Texas court, the party seeking relief must generally show both that the lower court’s action constituted an abuse of discretion and that “appeal is an inadequate remedy.” The first of those requirements, i.e., an abuse of discretion, is “fulfilled where a [lower] court acts without reference to guiding rules or principles or in an arbitrary or unreasonable manner.” As to the second requirement, i.e., lack of an adequate remedy by appeal, “no specific definition captures the essence of or circumscribes what [constitutes] an ‘adequate’ remedy.” Rather, the term “‘adequate’ is merely a proxy for the careful balance of jurisprudential considerations that determine when appellate courts will use original mandamus proceedings to review the actions of lower courts” and “its meaning ‘depends heavily on the circumstances presented.’” “[A]n ‘adequate’ appellate remedy exists when ‘any benefits to mandamus review are outweighed by the detriments.’”
Douglas S. Lang & Rachel A. Campbell, Survey of Recent Mandamus Decisions of the Texas Supreme Court, 5 SMU Ann. Tex. Surv. 407 (2019).