Damian was a private practice litigator for fifteen years, specialized in criminal law, with suspicious, rich and probably criminal clientele. Will Gardner offered him a partner place at Lockhart/Gardner after Alicia Florrick left the firm to form her own.
Damian befriended Howard Lyman and liked Will, who had given him chance of hiring in the first place. He presents himself as typical "bad boy", talking back to authorities, flirting with female co-workers and doing whatever he wants, causing Diane Lockhart to put Kalinda Sharma on assignment of tracking him. Damian and Kalinda constantly played cat and mouse, with Damian using help of his police friend Jenna Villette. He met Alicia on few occasions.
In an interview with Robert King and Michelle King, it was revealed that the character of Damian Boyle was intended to be Alicia's love interest after Will's death. Due to Jason O'Mara's casting in another series, that story arc was cancelled.