More like a mediocre episode of NYPD Blue than a feature film. David Caruso plays an assistant DA out to solve the murder of his boss. Linda Fiorentino is the ''Jade'' of the title, a supposedly irresistible combination of psychologist and hooker. Director William Friedkin can't do much with Joe Eszterhas' perfervid script; neither can Fiorentino, who's around primarily to illustrate an abstract concept: woman as predatory beast. She'd have fared better cast as a tiger in a National Geographic special.