Schier was added to the list in 1968, for participating in the kidnapping-for-ransom of land heiress Barbara Jane Mackle in a plan concocted by her boyfriend, Gary Steven Krist. Krist was arrested two days later while Schier, who had separated from Krist after a botched initial attempt to collect the ransom, escaped and was apprehended in Norman, Oklahoma 79 days after the kidnapping. She pled guilty and was sentenced to seven years in prison.
While Schier was in prison, Gene Miller, in collaboration with Mackle, wrote about the crime in 83 Hours Till Dawn. Schier's case was one of many covered in the 2002 book Mistresses of Mayhem: the Book of Women Criminals.