The current law won't allow for that kind of use, but a new bill headed for the state legislature aims to change that.
More than two dozen red light cameras keep watch over Seattle intersections, snapping photos when drivers run the light. By law, those images can only be used to prosecute traffic tickets, but investigators want to loosen the rules so police can check them for clues in other crimes.
One case where police think the cameras could help is the drive-by murder of Nicole Westbrook in Pioneer Square last April.
Surveillance video from a nearby store shows the shooter's car pass by just before Westbrook collapses from the gunshot.
"We have a side picture of the car. We have every reason to think that car ran a red light, and had we been able to get the red light picture of that car's license plate, my guess is we would have solved that case," said King County Prosecutor Dan Satterberg.
Police are confident Westbrook's killer went through at least two intersections with red light cameras. But under current law, reviewing the footage in any way would jeopardize their case.
"We then looked at the statute and the prosecutors and our detectives determined that if we even peeked, that would be a violation," said Assistant Seattle Police Chief Jim Pugel.
The ACLU says limits on red light cameras protects the public's privacy, and police and prosecutors are just trying an end-run around what the legislature approved.
"There are always arguments that if police had more powers, if they had drones, if they had you name it, they could solve more crimes," said the ACLU's Doug Honig. "When these cameras started out, the government made very clear assurances, 'Oh we're not going to use it that way,' and we don't think they should change now."
A new bill to change the law would still require police to get a search warrant signed by a judge before looking at the videos. Investigators say that would address most people's privacy concerns.
Rep. Chris Hurst is sponsoring legislation to eliminate red light camera restrictions, and that bill will head to a committee hearing next week.