An ex post facto violation occurs when a law is retrospective, i.e., it applies to events occurring before its enactment, and it disadvantages the offender affected by altering the definition of criminal conduct or increasing the punishment for the crime. (Lynce v. Mathis (1997) 519 U.S. 433, 441.) Serrato’s request for a sentence reduction so that she would be eligible to apply for the Board of Prisons Terms’ boot camp was granted. Upon successful completion of the highly regimented boot camp program, the participant was eligible for sentence reduction of up to six months. Before Serrato was actually accepted into the program, the program was terminated. Serrato’s ex post facto claim failed under a retroactivity analysis because her potential benefits had not vested.