Police using San Diego streetlamp cameras to investigate violent crime.

A streetlamp camera system designed to measure traffic flow is now being leveraged by San Diego police to fight violent crime across the city.

Installed in 2016 and first used by police in 2018, the system has now been used in 140 separate police investigations with footage from the cameras requested around 20 times each month. And the city plans to expand what it calls the “world’s largest smart city platform” by adding 1000 more streetlamp cameras by the summer of 2020.

As of now, about 100 investigative officers in the sex crimes, robbery, traffic, internal affairs and homicide units have direct access to the video footage. The department’s internal policy dictates that video should only be reviewed in connection with violent crimes and that officers outside of those units can only gain access if approved by a “designated authority,” according to Dan Diego’s Union-Tribune. Footage on the cameras is deleted every 5 days if not downloaded by officers for investigations.

“We’ve had a lot of success stories recently, a couple of convictions where people have actually seen the video through a defence attorney and they immediately took a guilty plea rather than go to trial,” Lt. Jeffrey Jordon, who oversees the program for the department, said recently.

The footage has also helped exonerate suspects, leading police to drop murder charges after video showed that a suspect had acted in self-defence against an attacker.