Third Time's The Charm
"It was an accident," insisted Ron loudly, over Ginny's screaming. "No, really! He just... slipped!"
"Slipped," repeated Dumbledore.
"I guess the floor was wet or something. Anyway, he shouldn't have been carrying a knife, should he?"
"I'm sure you can see how this looks bad," said Hermione apologetically.
"I'd never kill anyone," exclaimed Ron.
They all looked at him.
"Well, okay, yes, Mrs Norris... but she practically asked for it! Always watching me like that," growled Ron. "But Filch was an accident! It's not like I waved my wand and yelled 'Avada Kedavra' or --"
Green light flared.
"...oh, bloody hell!"
I'm having a very, very hard time not laughing out loud at work.