Can't provide a full answer but thought it was worth pointing out that witches in the Elizabethan era who were accused of killing someone were convicted as murderers, not for the crime of witchcraft. As such they were then hanged (not burned). Difference can be seen in this study of a local witch trial in Essex - http://www.witchtrials.co.uk/dumycz.pdf - mother and one daughter executed for murder, other daughter given a year in prison and six times in the stocks for bewitchment. (There are also some interesting statistics in there on the fact that female witches were more commonly accused independently, whereas males were about half of the time accused with female accomplices).

This is related to the structure of the 1542 and 1563 Witchcraft Acts which punished specific acts of 'maleficium', rather than specifically the idea of a compact with spirits or demons. As such the punishments were related to the harm caused.

For good sources, Keith Thomas' 'Religion and the Decline of Magic' is hugely important in the historiography. Malcolm Gaskill has an enormous body of work on this but I'm specifically using his 'Crime and Mentalities in Early Modern England'.