The proof they say is in the pictures, and one photo led to an arrest.
In April, Eddie Rocha noticed thousands of dollars worth of jewelry missing from his home.
Among the items stolen was a $2,000 designer watch.
The family immediately suspected it had to be someone they knew.
It turns out the suspected thief is not only a friend and classmate of Philemon Rocha's; it's his very next door neighbor.
Philemon's father made the connection after looking online at photos of the Darien High School Senior Prom.
That's when he recognized his watch in one of the pictures poking out from underneath the sleeve of the suspect's white tuxedo.
Rocha called police who arrested the 17-year old.
The suspect's identity is being withheld because of his status as a youthful offender.
Police say the teen has admitted to the theft.
Investigators still have the watch in evidence and have recovered other items, but most of the jewelry was pawned for cash.