Uhnak's first book was autobiographical Policewoman (1964), written and published while she was still a New York Transit Police detective.
Her debut fiction, The Bait (1968), received a 1969 Edgar Award from the Mystery Writers of America for Best First Novel (in a tie with E. Richard Johnson's Silver Street). ,The Bait was also made into a 1973 made-for-television film of the same title. It was followed by The Witness and The Ledger, which was adapted for the TV-movie and series Get Christie Love! starring Teresa Graves. All three novels featured Christie Opara, an NYPD detective assigned to the Manhattan District Attorney's Office, where Uhnak herself was assigned for many years.
Later works included Law and Order, which was made into a TV-movie starring Darren McGavin and The Investigation, which was adapted into a TV-movie, "Kojak: The Price of Justice", with Telly Savalas.
In her later years she suffered from depression. She committed suicide by a self-administered drug overdoes in 2006. She was seventy-six at the time of her death.