> could equally well mean that John threw the trash out while he was sitting in the kitchen Not a grammar expert and may be wrong, but I think technically it's

> could equally well mean that John threw the trash out while he was sitting in the kitchen Not a grammar expert and may be wrong, but I think technically it's unambiguous because you do actually need the while to make John the subject of the verb 'sitting' in that sentence. Of course you're right that in practice, especially in speech, it could be taken either way and is thus definitely ambiguous. One could argue that's all that matters, I certainly would, but just to be pedantic I thought I'd point this out ;-)