Tierney’s practice focuses on appeals. During law school, Tierney assisted in representing an elderly incarcerated client through the Washington Innocence Project in a case that established a new Washington standard for cruel punishment in conditions of confinement. She successfully argued in front of Division Two that the cruel punishment provision of the Washington Constitution offers more protection than its federal counterpart in the conditions of confinement context. In re Pers. Restraint of Williams, 15 Wn. App. 2d 647, 476 P.3d 1064 (2020). The Washington Supreme Court granted discretionary review and held for the first time that conditions of confinement which create a substantial risk of serious harm are cruel punishment unless reasonably necessary to accomplish a legitimate penological goal (In re Pers. Restraint of Williams, No. 99344-1 (Wash. Oct. 7, 2021)).

After her first year of law school, Tierney interned in the Violence Against Women Act Unit at Northwest Immigrant Rights Project. Before studying law, Tierney taught high school English literature at Casablanca American School in Morocco and English as a second language at a primary school in Vigo, Spain.