"in order for Oscar's version to be true, the Stipps have to be the only people who heard gunshots"
Oo. Now you've said that, it looks quite startling.
I am not sure I'd be able to hear a bat being struck inside a house more than one or two houses away.
Yes indeed. The defence have been working quite hard to progress the 'but the bat sounds like the gun!' though their test of this wasn't exactly top-notch forensics. But now the above statement makes it look like they'd have to prove that the witnesses heard the bat, but not the gunshot. Which was, even with the rubbish recording, significantly louder and sharper than the bat. I thought the bat sounded like a gun until I heard the gun.
But you're right (I think, without looking back). Mr Stipp is the only person who's heard two sets of bangs (I think. Please someone jump in and correct me if I'm wrong.)