Gosh, I don't know. It seems unlikely, but they certainly seemed fairly inept. I'm sure the Defence are going to tear into them dreadfully. I can't understand why the police would start randomly moving things around when they arrived on the scene.
Although, it was pointed out to me that if Oscar mentioned he thought there was an intruder, the police might have automatically checked the upstairs to see if there was someone hiding there. This might explain moving the fans to get to the balcony, checking behind the curtains, on the balcony, even under the duvet... Who knows? I certainly don't.
I do think there are lot's of holes in the Prosecutions case however. When the gun shots were fired, not having the prosthetics on whilst breaking down the door etc.