Not completely but I would go with the acting pathologist on this one as he is more qualified to make such a claim, he stated that there would be a fair amount of blood on the killer. Its not of course just that we have someone murdering someone in a woodland area,we have movement of the body as well as post mortem cuts and other strange things going on. We have the murderer putting himself in a position to have skins cells under his nails, his sweat on the body,clothes ect. We have other possiblities that he would have been scratched by the victim or damaged in some way and or by the shrubbery/trees in the imediate area. Im sure you can gauge just what im saying here that in a situation like was occurring at this point there are ample reasons why he should have a veriety of forensics placing him at the scene.
Is it possible to wash it off? all of it! well lets see he would also have to decontaminate everywhere he touched for instance( the police took apart the drainage system in his house), clean the carpets or floors in the house for instance you see what im getting at. Can he do all this ? even with the help of his mother it would be impossible to get rid of everything that may point to him having carried out this crime. There is a crime being discussed on this forum just now where there were microscopic bloodlets that led to the conviction, these must have existed in this case also as there was far more blood around as well as agitation of the body. So its not just what you can see that had to be washed off but everything else you can't.
So all in all I would sayit was impossible yes.