Well yes, I understand what such a test might identify, however, what I meant was, the absence or presence of blood in this instance wouldn't have had any impact on the investigation, so why would they bother conducting such a test?
Well yes, but much has been made of the absence of blood on Sheila's palms or fingers on here, although I'm not sure why.
I suppose it could have told them something - if anyone else's blood was on her hands, or if her own blood was on the palms, it might have had some bearing on what happened.