CINCINNATI – Sitting in his car, a man watched two girls leaving a Fort Thomas school so he could expose himself and follow them home.
But there was something else watching – something police say helped them stop a crime before it even happened.
An automated LPR -- or license plate recognition -- camera attached to a Fort Thomas police cruiser had already detected and recorded the man’s car prowling different schools over several days.
Because of this technology, police say they were able to arrest the man before a more serious crime was committed.
"Right after he admitted to it, we asked him 'why?' I asked him what was the next step, and he was afraid and he goes, 'I don't know, and I'm scared of that,’” Fort Thomas Police Lt. Rich Whitford said. "There's a good potential (it) would have escalated to maybe a kidnapping, maybe a sexual abuse or rape, I don't know. I'd rather not…we know we stopped his action."
Preventing crime before it occurs has long been the holy grail of law enforcement. But even if a Tri-State investigator gets on the scene after a crime has occurred, Whitford said the license plate reader database is like a window in time.
It allows the investigator to take a look back not only before the crime occurred, but also before the criminal knew they were going to commit it.
The man in this case later pleaded guilty after being confronted with photos of his car -- automatically captured and saved by the LPR system long before the girls reported that he was exposing himself.
"We had a picture of his car in this area at this date and time -- there was nothing he could do to disprove it or lie his way out of it,” Whitford said. "We presented all that evidence to this suspect, and he said 'yeah, you got me. You got me.'"
In a separate situation in September, a Cincinnati LPR camera caught an SUV with bumper damage 10 minutes after a hit-and-run crash that seriously injured a motorcyclist on Spring Grove Avenue.
Investigators later discovered the LPR database also had a shot of the same vehicle recorded an hour before the crash. In that photo, the SUV had no bumper damage.
In that instance, police didn't just find the suspect’s vehicle -- they had before and after photos that could lead to an indictment.
LPR cameras -- used by 85 Tri-State police departments -- don't just run a tag number. They also feed photos, times and GPS locations of every plate the camera sees into a massive database.
Covington officer Jen Rudolph says she scans about 1,500 to 2,000 license plates every day.
And last month, one vehicle’s license plate scan led to a big break in a case.
"It said 'used in a robbery and assault' and gave the description of the suspect in that incident," Rudolph said.
The victim, paralyzed for life, also had his car stolen – the same car that passed Rudolph’s LPR cruiser on Madison Avenue in Covington.
Rudolph said she would have never known the stolen vehicle was there without her LPR camera.
“It would just have been another vehicle that had passed me,” she said. "Once (I) realized that it was a stolen vehicle, that's when I decided it was going to be a felony stop, which is where we call him out from the vehicle at gunpoint."
Dahn, who was behind the wheel, is now charged with robbery and grand theft auto.
"(It has) given the family kind of peace of mind to know this guy's not on the street, he's not going to do it to somebody else,” Dahn said. “It was all because of a system that we were able to get on our vehicles.”
This system is now mounted on 134 police cruisers in the Tri-State area, silently recording license plates into a database that has both caught and cleared suspects.
"Not only does it help us prove that people are guilty, it helps us prove that innocent people are innocent," said Whitford.
But LPR cameras have not been used without controversy and concerns of privacy.
The Tri-State LPR database has more than 25 million records, and likely includes several photos of your car at different times and places.
Authorities say the system is not used for traffic enforcement, and can only be searched by police officers investigating legitimate cases.
The American Civil Liberties Union challenged the legality of keeping a database of so many innocent drivers, but developers of the system said records are purged once a year.
They also said records are not checked until you're either the victim or a suspect in a crime.