We've had Snape's Worst Memory...

[dolorous_ett]

...now who can help me find Snape's Worst Excuse
for taking out Dumbledore?

I can't think of anything more original than things like:

"Sorry, Headmaster, I didn't see you there..."

"I'm just pretending to be evil, you know - what's the matter with you people?"

"I'm sorry - it was a sudden muscular twitch. I get them a lot when I'm under stress."

"I just read the spell in an old book I found somewhere - how was I to know something like that was going to happen?"

I'm sure some of my talented readers can come up with something much better than these, and I'd love to hear them!

There are a lot of really quite good excuses for Snape around at the moment. What I'm looking for, however, are incredibly lame ones.