A judge should only instruct on manslaughter if the evidence would be consistent with such a verdict. I really really dislike the notion that a judge should interpret the evidence, but in the case at hand both the defense and prosecutor have effectively stipulated that TM's death was not accidental. If both prosecutor and defendant agree that the evidence is inconsistent with a manslaughter, I can't see any basis whatsoever for the judge to disagree.
Thanks, supercat.
Oh - and I covet your tagline! ;-P