I know the dead man's family might not think so but I wouldn't have a problem seeing that man walk free. Ya shag someone elses missus, you are taking a gamble. Unfortunate turn or events but there's only one man responsible for that.
A friends/aqaintance of mine brother was killed in Nottingham, last year I think, by a single punch. I believe he was accused of chasing another chaps partner/GF. It happens, you knock somebody out over concrete and their head has a 6ft fall onto it....