It's late at night and an Aurora police officer is making a traffic stop.
The officer approaches the vehicle, trying to determine how many people are inside. But the windows are tinted -- too tinted -- and it's impossible to tell.
Since a police officer was shot approaching a car several years ago, the state has set limits on how dark tinted windows may be. And in Aurora, which has had some high-crime years in its past, an inability to see inside the vehicle puts officers in unnecessary danger, authorities say.
It's also a hazard to motorists to not be able to make eye contact with another driver, officials say.
Taking advantage of a $200 device, Aurora police are writing tickets for excessively tinted windows at a breakneck pace: In the first five months of the year, they issued 291 citations; during that time a year ago, they wrote only two tickets.
"The big difference is the technology," Lt. Nick Coronado said.
Several other police departments use the same type of device, including Elgin, Lisle, Schaumburg, St. Charles and Vernon Hills.
But Aurora seems to be leading the most concentrated initiative against illegally tinted windows. Officers conducted several special checks for violations, writing tickets -- not warnings -- for all they found. But given the number of violations discovered, police also plan to hold an event that would allow drivers to have their windows tested for compliance without risking a $120 ticket compelling them to appear in court.
The state law regulating tint was intended as a precautionary measure for law enforcement after a police officer in LaGrange was shot in the face with a shotgun during a routine traffic stop, according to state Sen. Matt Murphy's staff. Murphy, a Palatine Republican, was one of the sponsors of a 2009 update to the law that actually relaxed rules about the level of tint permissible on side windows next to the driver and front-seat passenger.
The amount of tint allowed on a vehicle's front windows depends on the darkness of its back windows. The darker the back windows, the lighter the front windows must be in order to retain visibility, Aurora's Coronado said.
If a car's back windows have tint installed by the manufacturer or tint installed later that allows less than 30 percent of light through, then at least 50 percent of light must be able to shine through its front windows.
If a car's back windows allow more than 35 percent of light through, its front windows can be tinted more darkly, up to 65 percent.
Aurora police test a vehicle's compliance using a light transmittance meter. The device is placed on both sides of the window to get a reading, Aurora Sgt. Tom Hinterlong said. Suspicion of illegally tinted windows counts as probable cause to pull over a vehicle and perform the test.
"We're not measuring the tint; we're measuring the amount of light that comes through," Hinterlong said.
The patrol division of the St. Charles Police Department uses light meters in much the same way, spokesman Paul McCurtain said. In Schaumburg, a few meters are allocated to both the traffic and patrol divisions to be taken to stops as needed, Sgt. John Nebl said.
In Lisle, light transmittance meters have been used since shortly after the state law changed in 2009. But Cmdr. Ron Wilke said they're rarely used and officers don't find many vehicles with illegally tinted windows.
In Aurora, though, police are finding far more violators than in the past.
"We're finding a high majority of the people who have applied the additional tint, gone to the extreme darkness on it, are people who don't want to be seen or recognized by police," Coronado said.
Some of those people have had run-ins with the law, racked up too many traffic tickets and had their driver's license suspended or revoked, or they are known to police as gang members. Others aren't.
"It's not a steadfast rule that they're all involved in gangs," Coronado said. "It's a mixture of people."
Auto shops that install legal window tinting say hiding from police is not the motivation for most drivers. By applying a film to the inside of each window, drivers benefit from increased protection from UV rays, glare reduction and enhanced security, said Dan Doherty, owner and manager of Riggs Brothers Auto Tops & Interiors in Naperville.
"It does also protect the interior as well because UV rays can dry out leathers, fade materials," Doherty said. "It dresses up the vehicle's look as well as protecting it."
The problem with well-meaning window tinters is that they often forget to consider the factory-installed tint before adding a film to further darken a window, Coronado said. Even with 5 percent variation from the light transmittance required by law, that oversight can lead to violations.