BRAIN TUSSLE

After a local Post Office robbery, 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?

David said:
   It wasn't Charles
   It was Alan

Mack said:
   It was Charles
   It wasn't Alan

Charles said:
   It was David
   It wasn't Eric

Alan said:
   It was Eric
   It wasn't David

Eric said:
   It was Mack
   It was Alan

Hint: Remember that each person told exactly one truth and exactly one lie.

Answer:

Mack was the culprit.

Looking at David's statement if it was Charles, then David was lying in his first statement, which makes the second statement true. Which would mean that it was both Charles and Alan. So it can't be Charles.

Which means Mack was lying in his first statement, which makes the second statement true. Therefore it can't be Alan.

So Eric's second statement must be false, meaning his first statement was true, therefore it was Mack.