There wasn't much left of a 2008 Dodge Charger after a crash on Ogden Avenue last month. But one piece of the rubble confirmed what Naperville police suspected: The car was traveling really fast.
In fact, they say, it was doing 142 mph when it hit a curb and went airborne.
Police said the driver's speed just before impact was captured by what's commonly known as an event data recorder, or EDR. The devices are similar to so-called "black boxes" found on commercial airliners and come standard in most passenger cars and light vehicles manufactured today.
"We got a search warrant for it and obtained the data inside," Naperville Police Sgt. Gregg Bell said.
The case highlights a changing landscape for both drivers and law enforcement, as investigators turn more frequently to EDRs for raw data to reconstruct accidents.
Some automakers began installing the recorders in the 1990s to monitor air bag performance. They continuously record and erase data in 6- or 8-second snippets. When an "event" such as a crash activates an air bag, the most recent information is moved to the EDR's long-term memory for later retrieval. Everything from braking and steering to vehicle speed and even seat belt usage can be captured, experts say.
"It's another tool that we use," said Sgt. Craig Campbell of the Kane County Sheriff's Accident Reconstruction Team. "Essentially, it can support your (accident) reconstruction."
Campbell said the devices are generally no bigger than 1 square foot. They're often buried under a front seat or below the center console. Police use "data retrieval tools" to download the information -- a process that takes less than a half-hour -- once they've gotten authorization from a judge or the owner.
Most times, Campbell said, investigators are looking to confirm details they've already tried to establish. "The flip side is, if you're way off, you have to pause and take a look," he said.
Rusty Haight, a former San Diego police officer who trains law enforcement to use the devices, estimates roughly 90 percent of all cars manufactured since 2005 have recorders. Government officials put the figure between 65 and 90 percent.
Haight said the data collected has grown more detailed in the past decade but is still relatively minimal compared to information picked up by black boxes on airplanes.
"It's amateurish, but it's still so much more than we had 10 years ago to help us better understand wrecks," said Haight, director of the Collision Safety Institute in California. "The loop of data is typically a few seconds. But that's in the context of a crash -- and a crash lasts a tenth of a second."
In addition to the Naperville crash, DuPage County prosecutors cited an EDR last month in their case against a Carol Stream man who drove into a moving freight train, killing his girlfriend. Authorities said the data showed he sped up to 54 mph in the seconds before the July 3, 2011, crash in Itasca.
On the national stage, EDR data showed Massachusetts Lt. Gov. Timothy Murray was driving more than 100 mph before a violent crash last fall.
Starting Sept. 1, federal regulators will require automakers that install EDRs in model year 2013 vehicles to notify drivers of the recorders in owner manuals. The devices also must collect a minimum of 15 data sets, including vehicle speed, brake application, air bag deployment, seat belt usage and crash severity, according to the National Highway Traffic Safety Administration.
In addition, "we are considering development of a federal regulation that would require vehicle manufacturers to install EDRs," a safety administration spokesman said in a statement.
The agency said EDR data is "essential" for it to understand crash dynamics and how vehicles are performing: "We use this data to enact regulations that help save lives through improved vehicle safety system performance."
While police and prosecutors have widely embraced the technology, it has raised concerns among some civil libertarians.
Ed Yohnka, director of communications and public policy for the American Civil Liberties Union in Illinois, said the recorders "fit into a much larger piece of the intersection of technology and privacy that we've been concerned about for the past several years."
"Having that data in a car, candidly, is really a remarkable tool that can benefit us," Yohnka said. "On the other hand, it also raises serious questions about Fifth Amendment violations, self-incrimination and not being able to protect your own data, and having that data used against you. We ought to simply have that conversation."
Haight maintains "there's nothing to fear."
"There's nothing -- zero -- in the data recorded that identifies you as an individual," he said. "It's not going to say, 'Mr. Smith and Mrs. Jones were together.' This is objective. It doesn't have a dog in this fight."