There is an interesting view on how Scotland treated theft vs homicide. I particularly enjoyed the determination of the penalty due to the family of the deceased based on whether or not they were killed by a horse going backwards or forwards over them.

By the later medieval period you would more than likely be hung, or if the crime was notorious enough subjected to brutal punishment before death (see the punishment inflicted on Sir Robert Graham for his role in the murder of James I in 1437).

For sources of trials themselves and the period, there are a number of references in the link above that should help.

"Premodern" is a pretty big time-scale, as it is literally all of human history up until the last hundred years or so.

Care to narrow it down for us?