Hi Bill, I think this is not so clear. If they were still open minded (i.e. not "locked in") they'd never have been so aggressive on night of 5/6. I think they'd fixed on the staged break in within a day or two.
Unless you're saying Lumumba came into the scene a couple of days before the night interview of 5/6. But is there anything to show that he was on their radar before they trawled through Amanda's messages on that fateful night. Had they already been through her phone in a previous interview? In that case, they could have had a theory all sorted out and they just needed to create a situation where they would spring it on her and pressure her to spill the beans.
Those are two issues - the aggressiveness of the interrogation as opposed to when they got "locked-in" to the staged break in.
I'm not sure if Demspey argues this way or if it was the conclusion I drew to the way she argued....
I think the police got aggressive with Knox solely on the basis of Edda being on her way. They were already highly suspicious of Knox because of her "weird" behaviour, but the miminalists among the police would have kept their eye on the investigative path they were trying to solve - ie. the role if any that the known key holders might have played. (Please don't get diverted yet to the fact there could have been other key holders, it's just that Romanelli and Knox are known.)
Romanelli had weird behaviour of her own, she'd gone back into the crime-scene
after it had been secrued as one to fetch her laptop. Yet Romanelli had lawyered up, and was unavailable - esp. in the frantic pressure to close this case.
The assumed status of the break in as "staged" was only an investigative clue to follow Knox and Romanelli and nothing more. No need to lock it in, until.....
.... the police believe they only have one more chance with keyholder #2 before mom arrives with a lawyer like keyholder #1 had done. And as luck would have it, the "see you later" was aimed at Lumumba. There it was, the text-msg in black and white.
And guess what? Lumumba could no more manage a break-in than either Knox or Sollecito. It must have seemed to the cops that all the initial instincts had been borne out. "Wow, we really are smarter than we think! The break-in was staged after all!"
The aggressiveness of the interrogation, meant because Edda is on her way with the Cavalry, has paid off - it has also cemented the status of the staging of the break-in, only formerly hypothosized to narrow the investigation on to key holders.
Then again, once Guede is on the scene, why they didn't abandon the staging of the break-in as being necessary, is beyond me.