1. Like I have said over and over, I don't believe the prosecution's version of events, and I highly doubt it went down the way they said.
2. There are ways, including the simplest - putting something down under the victim so blood doesn't get on the garage itself at all, and disposing of it (plastic tarp or whatever). In general, I believe most people exaggerate the inafallibility of DNA evidence, from watching crime shows on TV. People are convinced that there is always collectible, indisputable DN evidence at every crime scene, and this is not always the case.
I think these are good ways to raise reasonable doubt, as the defense did. I just don't find them conclusive either way, asit seems some of you do.