Jim and John arrived at Lisa's house. John waited outside and served as a lookout while Jim stepped inside.
Jim shot Lisa and Richard. Jim did a guilty act, known as the Actus Reas. The Actus Reus and the Mens Reus were combined , this is called Concurrence. Lisa's friend neighbor and friend, Rachael, witnessed the murder.
Out of fear of Jim being convicted for murder, she agrees to help him hide the bodies.
JIM Principal In the First Degree Committed the murder
John Principal in the Second Degree Lookout, drove the getaway vehicle
Rachael Accessory After the Fact Helped hide the bodies
Steve Accessory Before the Fact Provided the firearm
Knowing Jim committed a crime, Rachael still helped Jim hide the evidence. By helping Jim, Rachael is now a Accessory After the Fact.
After the bodies were hidden, John drove Jim back home. By being the lookout and getaway driver, John is now a Principal in the Second Degree.