Now maybe he did leave at 9:30am. But talk about taking a chance! Any friend or relative could have stopped over at that time to drop off gifts, a bottle of wine, return something, just say hi, for coffee with Laci to say Merry Christmas............and if they did, what exactly does he say,............she's out walking the dog (ok, I'll wait) or she went to the store (ok I'll wait).
I would be more skeptical about the neighbor relating an accurate time. I see my neighbors coming and going constantly, but I don't immediately glance at my watch and make a mental note each time they back out of their driveway!
9:30am says alot without saying alot. It says WE had a leisurely morning, We had a quiet wake-up and breakfast, WE were ready to begin our day etc. 7am says no way a woman who is 8 months preggy is going to get up on a cold drizzly day and say, "Hey, I can't wait to take the dog for a walk!" OTOH if he strangled her in her sleep (or suffocated her) during the early morning hours of the 24th, he may have been so busy prepping the body and getting prepared for the drive to Berkely that he didn't get away until 9:30. But if that's true, he was certainly one lucky stiff no one interrupted him.