Little Johnny visits the police station

[rebbonk]

Johnny's infant school class was on a field trip to their local police station where they saw pictures tacked to a notice 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 man.

“Yes”said the policeman. “The detectives want to capture him very badly.”

Johnny asked,

Spoiler:

"Why didn't you keep him when you took his picture?”