I think you refer to the defendants in the criminal case.
The defendant has a right to apply for Royal Pardon, if he has been in a prison for a certain period of time as required by the regulations and also has shown good behavior. It is like a private application for the Royal Pardon.
Generally, on a special occasion, for instance, His Majesty’s the King’s Birthday, the King may grant the Royal Pardon, the reduction of punishment for all inmates, except for narcotic based convictions.