But how do we know the accused is the perp? "This is a terrible crime and therefore the defendent is guilty" is a favorite tactic of prosecutors with a weak case, after all.
I'm not saying he isn't guilty - I don't know if he is or not. But I do know that grisly details like these belong in the sentencing phase, after the defendent has been found guilty.
Details are necessary to get the conviction, no matter how awful or graphic, as they prove the elements of the crime.