Puzzle Details

The Post Office

After a local Post Office burglary, five suspects were being interviewed.

Below is a summary of their statements.

Police know that each of them told the truth in one of the statements and lied in the other.

From this information can you tell who committed the crime?

Brian said:
It wasn't Charles
It was Alan

Derek said:
It was Charles
It wasn't Alan

Charles said:
It was Brian
It wasn't Eric

Alan said:
It was Eric
It wasn't Brian

Eric said:
It was Derek
It was Alan

Since each suspect told the truth just once, Eric's statements mean that it was either Derek or Alan.

If it was Alan, then both of Brian's statements would be true, which isn't allowed (and similarly both of Derek's would be false).

Therefore it was Derek. This can be double checked with all of the other statements.

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