Tailboom,
From the police point of view, if the incident is deemed to be 'life threatening' or 'life changing' they are bound to treat the scene of the incident as a possible crime scene until it it proved to be otherwise.
That means the scene would have to be forensically examined and evidentially photographed and exhibits taken.
Obviously at the time the serious head injuries were deemed to be possibly life changing and therefore their hands were tied.
I hope that explains things a bit.
LM