To us, the right to a trial by jury is one of man's most sacred and natural rights. But it took man a long time to reach the point where this right was recognized. When the Normans conquered England in1066, they started a kind of jury were not there to listen as witnesses. They were supposed to decide a case on the basis of their own knowledge of the facts.
It was not until the reign of Henry II in the twelfth century that a big change was made. It was decided that the jury must decide a case solely on the evidence heard in court.
And this, of course, is the whole basis of the trial by jury system we have today. Twelve members of the trial jury listen to the evidence given by witnesses, to the arguments of the lawyers, and to the instructions of the judge. They then retire to a room to decide on their verdict. There seems to be no special reason why the number of jurors is 12, simply that Henry II in 1166 so decided and it has been that way since.
Before jury trials, trials were conducted in different ways. One method was "trial by compurgation". This meant that an accused person brought into court a number of neighbors who were willing to swear that he was innocent.
A second method was "trial by ordeal". The accused was subjected to all kinds of ordeals, like plunging his hands into burning oil. or carrying a piece of red-hot iron. If he survived the ordeal, he was declared innocent.
A third method was "trial by combat". Here a man had to do battle and defeat his enemy. If he won, he was innocent!