What are the cases governed by the Rules of Criminal Procedure?

Generally, the rules are to be applied to cases pending and remain undetermined at the time of their promulgation. They may not be given retroactive effect if they would affect substantive or vested rights. However, the rules may be applied retrospectively when they are favorable to the accused.

NOTE: These Rules should not diminish, increase, or modify substantive rights otherwise it would be a violation of the constitutional limitations on the promulgation of the rules on criminal procedure.