A policeman tests 3 men who are training to become detectives.
He shows the first guy a picture for 5 seconds then asks, "This is your suspect, how would you recognise him?"
The guy answers, "That's easy; he only has one eye!" The policeman says, "No, that's because the picture I showed is his side profile."
He flashes the picture for 5 seconds at the second guy. "This is your suspect; how would you recognise him?"
The second guy smiles and says, "Easy, he's only got one ear!"
The policeman angrily responds, "Of course only one eye and one ear are showing. It's a picture of his side profile!"
Extremely frustrated, he shows the picture to the third guy, "This is your suspect, how would you recognise him?
The third guy looks at the picture and says, "The suspect wears contact lenses."
The policeman is speechless because he really doesn't know himself if the suspect wears contacts or not.
He checks the suspect's file on his computer, and to his astonishment finds that the suspect was wearing contact lenses.
"Wow! The suspect does wear contact lenses. Good work! How were you able to make such an astute observation?" he asks.
"That's easy," the third guy replied." He can't wear regular glasses because he only has one eye and one ear."