Re: We passed the infinite monkey stage a long while ago
Only for very very long keys. As the key is re-used, it is unlikely to keep generating normal-looking text unless it was the right key. But sure, for a block the size of the key length you can come up with a key to generate any text you want.
So maybe, for an alibi for the innocent, make sure your message is longer than the key length.
On the other hand, for an alibi for the guilty, make sure your message is shorter than the key length and after the key length pad out with gibberish.
Maybe even have a "wrong" key which reveals the right message + gibberish and the right key reveals an entire other message and no gibberish.
Disclaimer: I don't know what I'm talking about