Hi Bob,
You bring up some good points., and I do like hearing your theories...
Personally I do believe that there is contamination, which could have occured intentionaly or by sloppy work in the lab. I am sure that it has happened before and will so again. And I do believe, after watching the video of the bra clasp being handled, that it could have been collected A LOT better. But I am no scientist. I just remember a case a few years back where a rogue Los Angeles police officer, Raffaele Perez was lying, planting and tampering with evidence, and heck, the cop even shot someone illegally. Over 100 convictions that prosecutors and judges/jurors worked hard on were overturned due to Mr. Perez's "work habits".
Since there is no evidence that Guede was in the room, he probably wasn't. I personally do not believe that he came in thru the window. I believe the window was broken to see if anyone was there. Heck, maybe Guede broke it when he first came by the apartment around 8:30pm, which is about 1/2 an hour before Miss Kercher returned home. But with it being early still, the chances would be greater to have been caught then, it would have made a loud noise which someone might have then investigated or even called the police. It would seem safer to break it later, after the bars/clubs had closed down and most people were asleep.
I have not studied the particulars of the apartment door, but I remember reading there was some problem with it locking. I figured it must have a lock on the handle, as most do, and so it's not that hard to lock it as one quickly leaves, just turn the knob or push the button in.
Then again, if there is someone else involved, who Miss Formica might have seen, maybe that person came back when Guede was in the bars/clubs afterwards? If he is a semi-profesional thief, such as the one who disconnected the alarm at the lawyers office, maybe he wore gloves then, too?
If Guede did not stab Miss Kercher, as Mr. Alessi states Guede said, well, he might not have been too bloody at the time, if at all. Maybe that's why he didn't leave blood, then. I wonder if he showered before he went out, if he did not stab Miss Kercher and have her blood on him?
RWVBWL