In the case of Scott Leslie Carmell v. Texas, the Supreme Court ruled that a law cannot be applied retroactively if it changes the amount or type of evidence needed to convict an individual. The court held this would violate Article I Section 10 Clause 1 (the Ex Post Facto clause) of the U.S Constitution which prohibits states from passing laws that increase punishment for criminal acts after they have been committed. In this case, Carmell was convicted in 1997 under a Texas statute enacted in 1993 allowing certain types of victim testimony as sufficient for conviction without corroborating evidence. However, at the time his crimes were committed (between 1991 and 1995), such testimony required corroboration under state law. The Supreme Court reversed his convictions on four counts because they relied solely on victim's testimonies without any additional supporting evidence as required by law at the time when those offenses occurred.

In the dissenting opinion for Scott Leslie Carmell v. Texas, Justice Ginsburg argued that the majority's interpretation of Article I, Section 10 was overly broad and inconsistent with historical understanding. She contended that this clause was intended to prevent legislative abuses by prohibiting laws which retroactively criminalize actions or increase punishments after crimes have been committed. However, she believed it did not apply to changes in rules governing evidence admissibility or trial procedures as these do not alter the legal definition of a crime or its punishment but merely affect how guilt is determined at trial. In her view, allowing such procedural changes does not violate fundamental fairness nor undermine public trust in law enforcement and judicial systems because they are part of an ongoing effort to improve accuracy and reliability of criminal trials.