SIOUX FALLS, S.D. (KELO) — One of the tools Sioux Falls police used in the investigation of Paul Billion’s death was the city’s traffic cameras.

Court documents say the cameras helped investigators map out where the suspects were the night he was shot.

There are more than 400 traffic cameras placed around the city.

The city’s first traffic camera went up about 12 or 13 years ago at the intersection of 41st and Louise.

“We wanted to get a better handle on traffic during all the peaks,” Traffic operations engineer Heath Hoftiezer said.

Today there are 425.

That includes vehicle detection cameras at intersections to run the traffic signals.

“It detects when cars or motorcycles or something pulls up so the intersection knows so the controller knows it needs to serve a particular movement,” Hofteizer said.

Traffic operations engineer Heath Hofteizer says the city also has observation cameras.

Those come in handy for monitoring traffic flow, but other departments have found them useful too.

For example, Sioux Falls police can use them for finding missing people or investigating crimes.

“If we have a crime happen in a certain area at a specific time, we can watch those areas and try to develop some information on vehicles, maybe people walking in the area, things that detectives have information on already, they can use that to kind of solidify their investigation and build it towards a success,” Sioux Falls Police Lt. Robert Forster said.

Just last week, the street maintenance division showed KELOLAND News how they use the cameras to monitor the roads when it snows.

“We’re all seeing benefits from what we’re doing, putting these out there in the streets, so it’s really taken off because of that,” Hofteizer said.