Riddles

[_Christian_]

Four people are suspected of stealing a diamond from a museum. If one of their statements is true, and the other false, whos the thief?

Bo said: It was Bo. It wasn't Roman
Roman said: It was Kate. It wasn't Bo
John Said: It was Roman. It wasn't Kate
Kate said: It was John. It was Bo

John!!

The statements create a logical paradox for everyone except John. True statements are green, false are red.