Every accessory before the fact to a serious indictable offence may be indicted, convicted, and sentenced, either before or after the trial of the principal offender, or together with the principal offender, or indicted, convicted, and sentenced, as a principal in the offence, and shall be liable in either case to the same punishment to which the person would have been liable had the person been the principal offender, whether the principal offender has been tried or not, or is amenable to justice or not.