Even if they had a witness, in most cases the dpp will drop charges down to manslaughter unless there is a reason. For example, look at the recent trial of Padraig Nally. He shot a man he caught on his land after beating him, and got 6 years for manslaughter. A good article on all this is located here:
http://www.villagemagazine.ie/articl...ud=38&aid=1186
The writer complains of a few recent cases where the person on trial is given a light sentence for manslaughter, but here, this is how we do it.