Irony:

Dramatic Irony ~ irony that is inherent in speeches or a situation in a drama.
Situational Irony ~ an outcome that turns out to be very different from what was expected.
Verbal Irony ~ a figure of speech in which what is said is the opposite of what is meant.
Ambiguity ~ doubtfulness or uncertainty of meaning or intention.

Response

1.) The author uses dramatic irony by having Mrs. Maloney use the leg of lamb to hit the top of her husband's head. She than gives the lamb to the police officers to eat it, and they would never suspected the leg of lamb to be the object used to kill Mrs. Maloney's husband. I found the situational irony to be more powerful because the police officer's were eating the object that killed Peter Maloney and they never suspected it.

2.) Mrs. Maloney is using verbal irony when she asked the police officers to do her a 'small favor'.

3.) The title is ironic because the definition itself means ''unaware of any impending catastrophe''.