Detective Lilly Rush (Kathryn Morris)
The lead character and for the first two seasons, the only female detective. She often appears the most empathetic of the detectives to the victims and often "sees" them at the end of the episode when their case is closed. Several episodes have suggested a troubled personal life: her father walked out on her family; she was attacked as a child; and she is estranged from both her mother (an alcoholic) and her younger sister (who slept with Lilly's fiancé and later her partner Scotty).
Detective Scotty Valens (Danny Pino)
Lilly's partner, introduced in the fifth episode, is the son of a Cuban father and Puerto Rican mother. The episode "Volunteers" states he was born some time in the 1970s, likely making him the youngest detective in the squad. Scotty is mentioned as having a number of siblings though only one, his older brother Mike, has appeared on the show. He has been shown to have a short temper at times, but is generally a loyal partner to Lilly. Like Lilly, he also has a difficulty with personal relationships: One girlfriend, Elisa, had some mental problems and eventually died in an apparent suicide. He later briefly embarked on a disastrous and ill-advised relationship with Lilly's sister Christina, which severely strained his friendship with Lilly for its duration.
Lieutenant John Stillman (John Finn)
The squad commander and occasionally a mentor and confidant to Lilly. He has shown himself to be stern but caring boss. His daughter was once assaulted, but survived and gave him a grandson.
Detective Nick Vera (Jeremy Ratchford)
A laid-back and occasionally uncouth detective, Vera is nonetheless an effective interrogator. Vera was a married man but was shown to become close to a number of women at times during cases, as he and wife had grown apart. A chance encounter caring for a baby in one episode led to him applying for adoption, possibly as a way to salvage his failing marriage. Ultimately, nothing came of this and he and his wife separated. He has also shown himself to be fairly suspicious of newcomers to the squad. One episode revealed him to be a big fan of the Rocky Horror Picture Show.
Detective Will Jeffries (Thom Barry)
Easily the oldest detective in the squad, Jeffries lived through many of the eras from which most of the show's cold cases take place. Jeffries was exposed to homicide at an early age when, as a boy in the 1960s, he discovered the body of a young black man who'd been lynched. He was married, though his wife died in a car accident in 1994. He is generally one of the more cool-headed detectives, though he was confined to desk duty briefly, after punching an ADA.
Detective Kat Miller (Tracie Thoms)
After assisting the squad on a case in the third season, Kat impressed Lt. Stillman enough that he offered her a position in the squad. Kat had previously been shot during an incident in Fishtown, though she claims to have emotionally recovered from that. She is the single mother of a young girl and a heavy smoker, though she claims she's trying to quit.
-Wikipedai, IMDB
