The following is from Æthelstan's (VI) London codex:
§1. Now again the king has been addressing his councillors at Whittlebury, and has sent word to the archbishop by Bishop Theodred, that he thinks it cruel to put to death such young people and for such slight offences, as he has learnt is the practice everywhere. He has declared now that both he himself and those with whom he has discussed the matber are of opinion that no one should be slain who is under fifteen years old, unless he is minded to defend himself, or tries to escape and refuses to give himself up. Then, he shall be struck down whether his offence be great or small"—whichever it may be. But if he will give himself up he shall be put in prison, as was declared at Grately" ; and he shall be liberated on the same conditions [as were laid down there].
§2 . If he is not put in prison, nonebeing available, they [his relatives] shall stand surety for him, to the full amount of his wergeld, that he shall desist for evermore from every form of crime. If the relatives will neither redeem him, nor stand surety for him, he shall swear, as the bishop directs him, that he will desist from every form of crime, and he shall remain in bondage until his wergeld is paid. If he is guilty of theft after that, he shall be slain or hanged, as older offenders have been.
§3. And the king has further declared, that no one shall be slain for the theft of property worth less than 12 pence' unless he is minded to flee or defend himself But in that case there shall be no hesitation, even if the property is of less value.
In short, repeated theft and resisting arrest. It's worth noting that a central theme of Æthelstan's reform is that he wants his Ealdormen and reeves to stop summarily executing theives when other legal penalties should apply. A common penalty for theft, especially thieves caught in the act, was actual penal servitude.
Acts of violence and killing could also carry the death penalty in Early Medieval England, dependant on context, period and kingdom. Under the reign of Æthelberht of Kent in the late 6th Century, violence on the King's property merely carried an additional fine, but by the reign of Ine in Wessex in the 8th Century, the law was far more severe:
If anyone fights in the king's house, he shall forfeit all his property, and it shall be for the king to decide whether he shall be put to death or not.
The laws of Wihtred of Kent (7th Century) held harsh punishments for theft:
- If anyone slays a man in the act of thieving, no wergeld shall be paid for him.
- If anyone catches a freeman in the act of stealing, the king shall decide which of the following three courses shall be adopted—whether he shall be put to death, or sold beyond the sea, or held to ransom for his wergeld.
§ 1. He who catches and secures him, shall have half his value. If he is put to death, 70 shillings shall be paid to him.
Interestingly, in contemporary Wessex, the law actually forbade the selling of Englishmen into foreign slavery.
Murder and theft did both carry associated weregilds - lit. 'man-money' - by which perpetrators were liable to pay recompense and a fine or face execution or retribution, but there was one notable exception. A death that was thought to have been caused by supernatural means was automatic grounds for execution. Æthelstan (II) states:
And we have declared with regard to witchcrafts and sorceries and deadly spells if death is occasioned thereby, and [the accused] cannot deny it [the charge], that he shall forfeit his life.