A CONTEMPORARY ACCOUNT OF HOW ALFRED THE GREAT DEALT WITH CAPTURED VIKING RAIDER, THE BATTLE PEAR-SHAPED AS THEIR SHIPS WERE NOT WELL SUITED TO FIGHTING IN SHALLOW WATERS

 a contemporary account of how Alfred the Great dealt with captured Viking raiders:The battle pear-shaped as their ships were not well suited to fighting in shallow waters.

This quote is from a larger passage in the chronicle, which describes a battle between Alfred's newly commissioned fleet and a small group of six Viking ships. 

The battle went pear-shaped for the English, as their ships were not well suited to fighting in shallow waters.  

Eventually, with both sides suffering losses, a few raiding ships escaped, leaving two undermanned ships being driven ashore on the coast of Sussex. 

The raiders were brought before the king and hanged, probably in front of a large audience, allowing Alfred to publicly play his role as protector of his people and their shared religion. 

Any captured Viking raider across Europe could probably expect similar treatment.

The more famous story regarding the capture of a Viking raider is the death of Ragnar Lothbrok (c. 865).

 Leading a small raiding party into Northumbria, he and his followers were defeated by the army of King Ælle, 

who ordered Ragnar's capture and execution by dropping him into a snake pit. This story is mainly a myth created in the 13th century.

 However, it again demonstrates that raiders were expected to be put to death, and it was the duty of the king in question to ensure royal justice was delivered upon those who attacked his kingdom, particularly pagans.