Scandinavian institution imported by settlement in the 9c and found afterwards at Lincoln, Stamford, Cambridge, York and other places in the *Danelaw. (The Latin term for the 12 jurors of York, described as hereditary lawmen, was hereditario jure lagaman civitatis.) Referred to in documents as judex and judices, also in *DB as lagaman, these 12 men gave judgement on cases, while also remembering and passing on local customs. Their persistence to the time of DB and after is a sign of heavy Scandinavian influence. As they expounded custom, it appears the office may have passed from father to son. In 1086, it would seem that some lawmen of Lincoln were sons of men who had been lawmen in Edward the Confessor's reign. Indeed, in the late 13c there are still lawmen to be found at Stamford. Another way of describing them might be as judgement-finders. Twelve remains the set number of jurors in an English court of law.
Dictionary of Medieval Terms and Phrases. Christopher Coredon with Ann Williams.