As she barreled her new Chevrolet Tahoe through construction signs and down the shoulder of the Schuylkill Expressway, police say, Brenda Jensen carried more than a bellyful of amphetamines.
Inside her 2008 SUV was a device known as an EDR, an "event data recorder," a small, carmaker-installed computer that captures information such as speed, braking and seat-belt use during a crash.
Jensen may not have even known it was there. Now, the device could be a witness against her - and potentially, as the use of EDRs grows, against anyone involved in a serious accident.
These ever-evolving machines are becoming standard equipment on new cars - an invaluable tool to law enforcement authorities, insurers and safety researchers, an increasing torment to lawyers and privacy advocates who see the boxes as silent police officers, always along for the ride.
Under current laws, auto manufacturers are not required to tell people whether their car has an EDR, which is similar to the "black box" on an airplane.
"It's a gold mine of potential data," said Anne McCartt, vice president of research for the Insurance Institute for Highway Safety, an industry group in Arlington, Va.
This month, state police charged Jensen, 37, of Wayne, with multiple offenses stemming from a Oct. 11 wreck that sent five people to hospitals and closed the westbound Schuylkill Expressway near Conshohocken.
Police said Jensen was impaired by amphetamines when she tore onto the shoulder, roared past slowing traffic, and smashed into a stopped state police cruiser, knocking it into other cars. Two troopers were among the injured.
At the hospital that night, Jensen told police she had no memory of the crash. But investigators thought they knew someone, or, rather, something that might. They got a search warrant to examine the EDR in Jensen's car.
Trooper Danea Alston, a state police spokeswoman and one of the first on the scene that night, said she could not discuss this specific case. But generally speaking, she said, "the black boxes have been very, very helpful."
An EDR can pinpoint a time or a speed that even an experienced accident investigator might have had to estimate. Drivers sometimes claim that their brakes failed, but, Alston said, "you can look at that box and say, 'Well, according to the machine, nothing failed.' "
Of course, EDRs aren't magical. They can't tell if a driver has been drinking, tore through a red light, or cut off another driver. And they're not mandatory, though they have been installed in nearly two-thirds of passenger vehicles built in 2005 and after.
General Motors, Ford, Isuzu, Mazda, Mitsubishi, Subaru and Suzuki put them in all their vehicles. More than half of Toyotas have EDRs.
But many people have no idea if their particular model carries the device, said Paul Stephens of the Privacy Rights Clearinghouse in California. "It's very concerning that what you're doing in your vehicle is being monitored and you don't know about it," he said.
The typical device records speed, brake use, accelerator depression, seat-belt use, air-bag deployment - and the number of collisions in a crash, since one accident may involve multiple impacts.
"Who owns the data?" asked Alisa Herman-Liu, a Swarthmore nurse whose family cars include a Volkswagen Passat, which doesn't have an EDR. "Can it be subpoenaed?"
The answers: It depends, and yes. In states that have laws on the issue, the EDR and its data belong to the person who owns the vehicle. But not all states have laws. And police agencies can almost invariably gain access to it. That's why ownership and access are at the forefront of the privacy debate.
For prosecutors, the machines have opened a new line of attack, enabling them to cite the black box as an impartial witness.
In 2005, a Florida court upheld the conviction of a man who crashed his Pontiac Grand Am into a car holding two teenagers, killing both. The EDR showed he was driving 103 m.p.h. just before the crash.
The defense argued that the data did not match other physical evidence in the case.
Not everyone is enamored of EDR technology - or believes it infallible.
"They're right most of the time, almost all the time," said Jeffrey Wigington, a lawyer in Texas. "But I think people in law enforcement agencies view them as 100 percent accurate, and they're just not that precise."
The machines have "some real quirks," said Wigington, whose cases involve alleged car defects that result in death or catastrophic injury. In some Fords, he said, if the ignition is switched on after a crash, the EDR memory may be overwritten.
The modern EDR grew out of research begun in the 1970s, as carmakers tinkered with sensors that could reliably trigger air bags. The big carmakers, technical editor Warren Webb explained in Electronics Design, Strategy, News, knew customers wouldn't pay extra for a safety item if they didn't believe it actually made them safer. As air-bag controls grew more sophisticated, so did the ability to gather data, Webb wrote.
One early court test involved the reliability of the black box in the Corvette of Eagles star Jerome Brown, who died in a one-car crash in Florida in 1992. In 1999, Brown's survivors sued GM for $30 million, claiming the air bag in his car deployed when he hit a pothole, causing him to smash into a tree. However, black-box data showed the air bag went off, properly, on impact, and the family lost the case.
EDRs have evolved enormously since then - and will continue to do so, said George Hoffer, a Virginia Commonwealth University professor who studies the auto industry.
"It's the ultimate Big Brother," he said. "Where does it stop?"
Hard to say.
But McCartt, of the Insurance Institute, hopes privacy concerns can be assuaged, as the black box is too valuable to limit its use.
"EDR data just have really enormous, almost unlimited, potential to help us understand information about crashes," she said.
So, does her car have one?
She paused. "I don't know."
Contact staff writer Jeff Gammage at 610-313-8110 or firstname.lastname@example.org.