It happens all the time..
(Not saying it happened in *this* case, but it happens a lot. It's the undoing of a lot of criminals.)
Yes! Exactly, murderers think they won't get caught! Some of my friends and I (locals) were just discussing MB today and we said it had to either be a dumb man child vandalizing and got caught off guard or a family member that did it. And soon hopefully the real or other COD will be posted and that might tell/show how the blood/dna was transferred.