Possible Clues:

• Whodunit staple
• It means 'elsewhere' in Latin
• It's best when it's airtight
• With this one was not all there at all
• By the alley, by the sound of it, you're not there
• Excuse from a politician (independent)
• Primarily, accused party may need one?
• Play by Michael Morton, based on the Agatha Christie novel 'The Murder of Roger Ackroyd'
• A coalition party's current excuse for failure
• Courtroom evidence