Brían F. O'Byrne stars as Homicide Detective Reg Duffy in NBC's gritty crime drama "Prime Suspect."

O'Byrne is a Tony Award-winning Irish actor and was most recently seen co-starring alongside Joseph Fiennes on "Flash Forward" and alongside Kate Winslet in the miniseries "Mildred Pierce." O'Byrne also appeared as a series regular on "Brotherhood."

O'Byrne's big screen credits include "The International," directed by Tom Tykwer, Antoine Fuqua's "Brooklyn's Finest", "No Reservations" and Sidney Lumet's "Before the Devil Knows You're Dead" opposite Ethan Hawke.

On Broadway, O'Byrne last starred in Tom Stoppard's groundbreaking trilogy, "The Coast of Utopia," directed by Jack O'Brien, also starring Ethan Hawke and Billy Crudup, for which he received his fifth Tony nomination as Best Actor in a Play for his performance.� Additional stage credits include William Friedkin's adaptation of the Off-Broadway play "Bug" for Lion's Gate, opposite Ashley Judd and Harry Connick, Jr. In 2004, O'Byrne won a Tony for his portrayal of a murderous pedophile in "Frozen."

O'Byrne credits his training at the Samuel Beckett Center, Trinity College in Dublin for his many successes.