Caitlin Halligan, former general counsel to the Manhattan District Attorney’s Office, joined Gibson Dunn & Crutcher this week as partner focusing on appellate litigation.

Halligan left the DA general counsel post in January, after four years of helping oversee more than 500 lawyers and providing advice to the district attorney on significant cases and legal issues. Halligan, 47, was nominated by President Barack Obama to serve on the U.S. Court of Appeals for the District of Columbia Circuit, but Republicans twice blocked her nomination. She was previously a partner at Weil, Gotshal & Manges and solicitor general for New York State.

Halligan said in an interview that Gibson Dunn “offered a unique opportunity in terms of the tremendous strength of the litigation practice nationally and especially in New York, and it also has a truly excellent appellate practice.”

“Those two factors together for me were tremendously attractive,” she said.

Halligan has argued five cases before the U.S. Supreme Court. Gibson Dunn chairman and managing partner Kenneth Doran said in a statement that Halligan will join an appellate team where five lawyers have argued seven cases during the Supreme Court’s 2013 term.

Robert Serio, co-partner in charge of Gibson’s New York office, wrote: “[Halligan] is an immensely talented litigator with unmatched credentials. She will add needed capacity not only to our appellate and litigation practices, but also to our white-collar practice, given her career in the public sector and her experience with criminal law issues.”