Final Truth by Mariah Stewart

Reagan Landry has spent the last two years going through her father's notes and files, writing a book and researching a puzzle left behind by her father. Realizing she needs help, she hires an assistant to help her organize things. In the meantime, bad boy Lester Ray Barnes is on death row, counting the days until needle time, when news breaks that the DNA testing center responsible for Lester's conviction has been exposed for fabricating reports. Lester wants free and wants Reagan to write his story. Reagan is interested in this event and agrees to look into Lester's circumstances discovering a witness was coerced by a cop. Mayhem breaks loose when Lester is freed and murders begin. Has Reagan unwittingly played a part in the rape and murder of these women? Stewart writes a cunning tale of crime unleashed when people lie. A good mystery.