Carmen Goldsmith was driving her BMW through Inglewood, a Los Angeles suburb, when she ran a red light. She instantly became one of countless people nationwide ticketed by a red light camera.

The California woman challenged her citation in a trial court, where she was found guilty and fined $436. She appealed and lost.

She based her argument in part on the fact that courts had previously overturned two other red light camera cases in Southern California. In those, appellate courts agreed that a testifying officer had no personal knowledge of how the automated data was collected or whether the camera was working properly at the time. So the evidence of traffic violations was thrown out.

Goldsmith's case, The People of California v. Goldsmith, is a 5-year-old legal odyssey scheduled to be heard on Thursday (today) before the California Supreme Court in Los Angeles. The court’s verdict likely will put to rest the admissibility of red light camera evidence in the country’s most populous state, where red light violations are by far the highest. (Typically they’re in the $100 range in the rest of the country.)

As Ars recently reported, red light cameras have reached a turning point across the United States. According to the Insurance Institute for Highway Safety (IIHS), a non-profit largely funded by auto insurance companies, last year was the first time in nearly two decades that the number of American cities with red light cameras had fallen—the systems were installed in 509 communities as of November 2013.

While a single-year drop may not ultimately mean much, legislators across the country are increasingly agitated about the cameras. Bills are also pending in Florida and Ohio that would ban the devices entirely. A state representative in Iowa has also twice introduced legislation to ban red light cameras (he was not successful). Part of this backlash has to do with the perception that red light cameras are a moneymaking scheme, pure and simple.

The case before California's high court is being closely watched, drawing amicus briefs on both sides in considerable numbers. A notable one comes from Redflex, the company that Inglewood and many other California municipalities contract with to employ their red light camera setup.

“In fact, based on our research, we have not been able to locate any other infraction case in the history of this state that generated so many amicus briefs on both sides over a $436 citation!” Goldsmith's lawyer wrote in a petition to the court.

Hear me now

The California Supreme Court is hearing the case in an attempt to answer three basic questions:

What testimony, if any, regarding the accuracy and reliability of the automated traffic enforcement system (ATES) is required as a prerequisite to admission of the ATES-generated evidence? Is the ATES evidence hearsay? If so, do any exceptions apply?

The question of hearsay is an important one: American law does not recognize secondary witnesses—people who say that someone else told them something—to establish factual evidence.

Goldsmith’s attorneys argue in their opening brief that the evidence against her was hearsay:

First, Goldsmith’s constitutional right to confrontation was violated because the Redflex technician in charge of preparing the evidence package did not even bother to show up at Goldsmith’s trial. Neither did the police department employee that allegedly operated the red light cameras system. As a result, the “investigator” sent by the prosecution to trial as the sole witness was a secondary surrogate witness that testified in lieu of the primary surrogate witness (i.e., the police department employee that allegedly operated the system). Consequently, Goldsmith’s conviction cannot be upheld based on such “double surrogacy.”

Therefore, they argue, the evidence needs to be properly authenticated by a Redflex technician before it can be entered into evidence. Without such evidence, the case falls apart. What's more, Goldsmith's attorneys argue that she has the constitutional right to face her accuser. In this case, her accuser is a machine. Her counsel also argues that Redflex’s camera system has a prior record of falsifying speed camera documents (PDF) in Arizona.

Machines can't talk, but data speaks volumes

Attorneys representing California's side have a different view.

In their reply brief, they argue: "ATES-generated images are original digital images that are just like other film photo or video evidence being offered as probative or 'silent witness' evidence, and they should be authenticated in the same way."

They also maintain Goldsmith has no right to confront her accuser in court:

Because ATES-generated evidence is not created using any human input, it is also not a “statement” of any kind, meaning that it is neither hearsay nor subject to a Sixth Amendment Confrontation Clause analysis.

California concludes that machine-generated evidence "will only become more commonplace in the future, is not equivalent to a human statement, and so cannot be subject to either the hearsay rule or the Confrontation Clause."

Perfect enforcement

Goldsmith is basing her case largely on two other cases, People v. Borzakian (2012) and People v. Khaled (2010). California appellate courts agreed that the Redflex red light camera did constitute hearsay and violated confrontational rights of the ticketed.

Richard Allen Baylis, a veteran Orange County attorney who defended the 2010 case, said the fundamental issues in all three cases are the same: “It really comes down to what does it take to authenticate the photograph?”

Baylis, who handles by his own estimation 300 to 400 such cases a year in Orange County alone, said that county authorities have changed their practices and mandated that Redflex employees and a prosecuting attorney appear in court, which is typically not the case in the rest of the state.

“If [the California Supreme Court] reverses on Goldsmith, I think that it's going to do a lot to kill the red light cameras in California, not so much that they couldn't get the evidence in, but it's going to get a lot more difficult for them,” he said. “[Cities] are going to have a Redflex employee at every trial and a prosecuting attorney at every trial and that would push their costs up.”

Goldsmith has much broader implications for the future of automated law enforcement too, from license plate readers to any other future robotic technology.

“This is the first case I’ve seen precisely along these lines,” said Woodrow Hartzog, a professor of law at the Cumberland School of Law at Sanford University in Alabama.

“So one thing that’s interesting to me is that there’s this challenge to this image, it strikes me that there is nothing truly exceptional about a video camera as a surveillance system. But that’s not the only thing that a red light camera does. There’s an algorithm that monitors when a car has violated the law.”

Hartzog has been at the forefront of new scholarly and legal considerations of the implications of automated law enforcement systems.

“We really should not be seeking to pursue all laws with the same vigor,” he said, pointing out that while it may be desirable to catch all murderers, it may not be desirable to catch all jaywalkers even though both are illegal.

“The sooner we come to that notion and embrace a mentality that good enough enforcement is the most desirable for a lot of different laws, then we can have a conversation about how we want these automated systems to be calibrated. There are a lot of grace periods that we recognize as a norm, like five miles per hour over the speed limit. Do we want to build those into the system?"

A ruling in Goldsmith's case is expected within 90 days.