MOO, but I suspect it's something like a certain volume of blood ( or evidence thereof) or something like brain tissue. Something that there's no other reason for it to be there. Kids get bloody noses, they vomit and poop and pee, but unless they bleed out or have severe head trauma, you don't find blood pools, or brain matter. I don't wish on him a brutal, violent, bloody death, but they seem very sure he's dead, and we know they luminoled the house at least once. Twice? I don't remember. But then, there's no arrest, and if it was so bloody, I don't know why they wouldn't have arrested her at this point.