Principle offender vs accessory

Question 1

what is a principal offender and how can they be found guilty

Answer 1

They commit the actus reus and they can be found guilty is they assist, plan or encourage, or direct the crime/offence

Question 2

what is an accessory to a crime and how can they be found guilty

Answer 2

After the act they help the offender avoid the legal system and they can be found guilty if they help the offender avoid being held liable after they commit the crime