Justice Hart was on the Colorado Supreme Court from 2017 to 2026. Prior to being appointed to the court, and beginning in 2000, Justice Hart taught at the University of Colorado law school in the areas of employment discrimination, access to justice, and constitutional law. She served as director of the Byron R. White Center for the Study of American Constitutional Law from 2010 to 2017. 

A 1995 graduate of Harvard Law School, Justice Hart clerked for Judge Guido Calabresi of the Second Circuit and for Justice John Paul Stevens on the U.S. Supreme Court. Melissa Hart practiced law for several years in Washington, D.C., including as a trial attorney at the U.S. Department of Justice.