Top Ten Most Wanted

Little Johnny's kindergarten class was on a field trip to their local police station where they saw pictures, tacked to a bulletin board, of the 10 most wanted criminals.
One of the youngsters pointed to a picture and asked if it really was the photo of a wanted person. 
"Yes," said the policeman. 
"The detectives want very badly to capture him." 

Little Johnny asked, "Why didn't you keep him when you took his picture?"