The Illustrated Guide to Criminal Law
Chapter 9: At Least You Tried
Attempt pg 23: Limitations of Impossibility

But Frick and Frack, on the other hand, do not have that defense.

Frick planted a bomb in your mailbox (what is it with you, anyway?). The bomb’s fuse was defective, however, so it couldn’t go boom.

Older man placing a cartoon-style bomb in a mailbox

He’s trying to commit the crime, but it’s impossible. Unlike Joe, however, he could have succeeded but for circumstances beyond his control (or of which he was unaware). Frick is still dangerous, and so he’s still guilty.