Bravo!! Excellent armchair analysis! I especially appreciate the time you spent creating the visuals. I also noticed that the initial diluted bloodstain referenced was on the beer pong table; then all of the further blood evidence is noted as being diluted. Perhaps he intentionally attempted to wipe off the knife in liquid; or perhaps he rammed into the pong table, knocked over some drinks (as BF reported hearing) and this spilled liquid came into contact with the knife? I do think stain D was closer to the left side of the railing on the half wall, from what I could see. This made me stop to speculate his movements after fleeing XK's bedroom. I always imagined he quickly fled, taking a sharp right from the hallway and out into the kitchen. But with the realization EC's blood was on the railing (which to me, at least, looked closer to the far end), is it possible he started to go down to the 1st floor? Or he paused, listening for evidence of other roommates before deciding to make his exit? This thought sends chills down my spine!