Yeah I don't think anyone was happy with the way that ended. Except for those miserable bastards who never liked Lumen.

I don't think he was "so completely sure," just pretty damn sure. Which is an important distinction. I mean where else would he have gotten a full-on blood drop on his shoe? How much dripping blood are you around on a regular basis? I mean, I'm rarely around dripping blood and I'm a female. Are you a cutter, Wes? Do we need an intervention?
I have a tap for dripping blood for when I want to play Dexter.

Anyway, you're not a police officer working in homicide in Miami. I just don't see why he was "pretty damn sure" the blood came from that particular crime scene rather than any other. Or maybe he scraped his knee, or bumped into someone else who did. It just seems like quite a leap from Quinn's perspective when you consider only what Quinn knew (admittedly it was much less of a leap from Laguerta's perspective after Quinn refuses to talk and then she saw blood).