The keys at the front desk

In Parliament every key hangs on a board, each on its own hook. On the night of the break-in there was an empty hook and nobody remembers who emptied it. Four people and one piece of evidence: one person per row, one per column. Whoever is left alone with it in the same room is the one you're looking for.

Suspects

• Alcina, the doorkeeper: She keeps the keys to every office on a board. That night the board had an empty hook.
• Bernardino, the night security guard: He does his rounds at two and at five. At half past three he was watching the football.
• Cristina, the cleaner: She starts at six with the leader's office. That day she started at five past six and everything was already turned over.
• Dâmaso, the legal adviser: He works late and always leaves by the back door, out of habit.