Changing a disciplinary sanction

A chairperson in a disciplinary hearing finds an employee not guilty of a serious transgression while senior management believes the person should have been found guilty. Or the employee is found guilty but, contrary to what the employer expects, is given a sanction short of dismissal. May management interfere and, for example, conduct a fresh hearing before another chairperson? May a sanction less severe than dismissal be increased and, if so, must a further hearing be held before this can happen?