The eastern region of England, between the Thames and the Tees, conquered and settled by the Danes in the 9th century, in which the customary laws observed in local courts were strongly influenced by Danish legal customs. The word is derived from Old English Deone lage (Danes law), which is first known from a charter of 1008. The exact borders of the Danelaw during the Viking Age are uncertain, but in the 12th century it was defined as the fifteen counties of Yorkshire, Nottinghamshire, Derbyshire, Leicestershire, Lincolnshire, Northamptonshire, Huntingdonshire, Cambridgeshire, Bedfordshire, Norfolk, Suffolk, Essex, Hertfordshire, Buckinghamshire and Middlesex. The first recognition that different legal customs prevailed in the Danish-ruled areas of England comes in the peace treaty between Alfred the Great and Guthrum, the Danish king of East Anglica in 866-890. These differences persisted for about 200 years after the West Saxon conquest, and in 970-4 king Edgar officially granted legal autonomy to the Danelaw.
Place-name evidence shows that the Danes did not settle the whole of the Danelaw intensively and were probably a minority of the population in most areas. But while they did not displace the majority of the native population, the Danes did take over royal and aristocratic estates wholesale and formed a new social and political elite that had a lasting influence on local customs. In local administration, the hundred (the basic unit for the administration of justice in England) was usually called a wapentake, and the hide (the area of land needed to support a peasant family) was generally known as the ploughland. (OE plogesland). The law of the Danelaw was distinguished from English law by procedural differences, heavy fines for breach of the king's peace, and the use, unknown in England at the time, of sworn aristocratic juries of presentment to initiate the prosecution of criminal suspects in wapentake courts. While under contemporary English law the most serious crimes could be tried by ordeal, in the Danelaw trial by combat was normal. There were also major differences in the landholding in the Danelaw. At the time of the Norman Conquest there was an unusually high number of peasant freeholders or 'sokemen' in the Danelaw compared with the rest of England. In Lincolnshire they accounted for nearly fifty per cent of the population, and in many other Danelaw counties it was around a third. Many sokemen were driven down into serfdom during the Norman period.
Notes from Encyclopaedia of the Viking Age by John Haywood. Thames
& Hudson 2000. pp 51-52.