Considering how much time passed between the murders and DW being found, he could have washed the tops of his shoes.BBM. One of the problems I have with Wint doing the slashing is that, while it seems blood was found on his shoe, it seems to have been little to the point he didn't see it. Which makes me think he may have stepped into the blood at some point and didn't realize it. I would think a slasher would have blood on top of his shoes.
JMO