Christopher “CJ” Precopia, 21, was stunned when police arrested him at work in 2017, accused of violently attacking his ex-girlfriend Faith Cox. She claimed he broke into her home, cut her with a box cutter, and carved an “X” into her chest. CJ faced up to 99 years in prison.

But he was 70 miles away at the time—at a hotel with his mom and friends. A selfie his mother posted on Facebook just 18 minutes before the alleged attack proved it. The photo’s timestamp and location cleared him, and prosecutors dropped the charges.

Nine months after his arrest, Cox was charged with filing a false report. CJ, now in the Navy, says the experience shows how easily lives can be upended by false accusations—and how a simple photo saved his.