Answer:
proof beyond a reasonable doubt
Explanation:
(To put a little bit of context, Magna Carta was created in 1215. Which means that this case happened before Magna Carta was created.)
Before the creation of Magna Carta, the King of England has the highest supremacy regarding all matter in the country.
This means that He will make all economic decisions, he arrange the group of people that will act as the executive groups to carried out the laws, and He also acted as the highest judge, jury, and executioner.
So, if the King personally think you were guilty, there is nothing you can do to change the decision. Regardless of how much evidence you have in your favor. If the King felt that you deserve a death penalty, than you will instantly executed.
After the creation of magna Carta, western societies started to acknowledge that the law should held the highest authority in every legal proceedings, not a single person.
This view is carried out to modern day legal system. To prevent us from throwing up innocent people to Jail and waste their lives jail, We must assume that those people are innocent until we can proof beyond a reasonable doubt that those people is guilty.