Where a witness in a summary prosecution is examined on oath in a case in which the accused is charged with an offence under any statute, and where the same witness is examined at the same diet in subsequent cause against the same or different persons accused of offences under the same statute, it shall not be necessary for the judge to administer the oath to the witness in the subsequent cases, but it shall be sufficient that the judge shall remind him in each case that he is still on oath.