In medieval England, frankpledge was a system of law enforcement and policing in which members of society were mutually responsible for the behavior of their peers. The system included everyone in the community but the highest nobility and their households.
The origins of frankpledge may stretch as far back as early Anglo-Saxon England, when a rudimentary jury system allowed for an accused man's neighbors and peers to vouch for his innocence or guilt. This idea was fixed more firmly in the 11th century, when King Canute II declared that every commoner, whether free or serf, must be part of a hundred that could ensure the good behavior of their members. The frankpledge as so described was more common in the Danelaw; in the south and southwest of England, tithing (with groups of ten men, more or less) was the norm. There is very little evidence to support the existence of frankpledge or tithing in the part of Britain north of Yorkshire.
Whether in frankpledge or in tithings, the groups involved followed a similar system. The groups were led by a capital pledge or, in the case of tithings, a tithingman. Whenever any member of the group was charged with a crime, it was the responsibility of the other members to see to it that he appeared in court to answer for it, or, failing that, to financially compensate any injured parties. It was also the responsibility of the group to bring to the attention of the court any crimes that they knew that any of their members had committed. This was done by the group leaders together, acting as a jury who represented the community; in this action can be seen the seeds of the modern-day Grand Jury. The groups and their leaders might also identify crimes that had been committed by individuals who were not in their own groups or, more commonly, who were outside the frankpledge/tithing system altogether.
Tithings and larger groups were probably organized around neighborhoods. These groups would meet on a fairly regular basis to conduct "views of frankpledge." In a view of frankpledge, members would survey the community to ensure that all adult males were members of a tithing. They would also take oaths not to engage in anything illegal, and they would hear charges of crimes and any other matters that needed to be brought before the court.
Although important individuals (nobility) were not part of the frankpledge system, the members of their households formed a kind of tithing, with the head of the household responsible for their behavior.
While initially frankpledge included both free men and serfs, by the 13th century, only unfree and landless men were required to bind themselves to a tithing or other group. For freeholders, their land was a sufficent pledge for good behavior. In the 14th century, when local constables operating under the new system of justices of the peace became more prevalent, frankpledge began to decline. It disappeared altogether by the end of the 15th century.
Note: the term "tithing" as used in relation to the frankpledge should not be confused with "tithe" and the system of tithing for the Church, in which individuals donated ten percent of their income.