|Division||Brooklyn Narcotics Division|
|Family|| Unnamed wife|
Jill Foster (daughter; deceased)
Sergeant Frank Foster is Captain Cragen's friend of 30 years and former partner.
Frank entered the academy the same year as Donald Cragen and the two remained close friends after graduation. When they were both rookies, Frank saved Cragen's life in East New York. When Frank got married, Donald was Frank's best man at the wedding and they eventually had two kids and was promoted to Sergeant for Brooklyn Narcotics. His daughter, Jill, eventually grew to hate her parents and starting doing drugs to rebel against her father. When Frank discovered her habit he tried to get her to stop to protect his career. When his Jill ran away he filed a missing person's report. When they failed to find her he grew more worried and agitated.
When Jill's photo appears on a website run by Tito Frank, he takes his wife and son to see Tito and pulls out his gun demanding to know where Jill is. ESU arrives at the scene and they bring Captain Cragen to be the negotiator. The minute Cragen talks to Frank, he lowers his gun and peacefully surrenders after Cragen promises to find Jill. After Tito shows them the video where Jill appears in and tells them about Lance Kanick, Cragen takes Frank's gun and he is arrested.
Captain Cragen later visits Frank in Rikers and they talk a little about his case before they start discussing Jill's home life. Cragen is hurt he didn't come to him about his troubles but Frank just recounts how his job affected Jill's drug habit to spite him. After Cragen mentions Frank is a good man, he asks him if he ever abused his daughter and Frank says he was never physical with her but he didn't respect her and called her things like "loser junkie". Cragen tells him he will try to work a deal with ADA Cabot to get him out, but Frank doesn't care and just wants his daughter back. When Jill's overdosed body is discovered, Cragen told him personally that Jill was dead and Frank breaks down crying. (SVU: "Runaway")