Editor's note: Since 2016, ESPN has probed the future of sports betting in a special multi-part series. Part nine looks at how facial recognition cameras -- an emerging tool for law enforcement and private security -- may play an increasing role in the legal United States sports betting market, especially involving in-game wagering using real-time data.

A few spectators for the US Open finals in New York's Flushing Meadows last month probably weren't smiling for the cameras.

Why not?

Because facial recognition cameras may have been scanning the seats looking for people transmitting real-time betting data to far-flung international locations, according to a disclosure earlier this year by the United States Tennis Association (USTA), the organization that runs the U.S. Open.

The USTA is "[e]xploring opportunities to utilize facial recognition software to identify known courtsiders at the U.S. Open," wrote the USTA in an April report about tennis integrity and gambling corruption.

So-called "courtsiders" -- some of whom have donned fake mustaches and other disguises to evade detection at tennis tournaments -- help bettors and data brokers seeking a speed-based edge by transmitting data to their clients faster than "official" sources. In some instances, this allows bettors to place bets that will be sure winners (for example, the winner of a specific point), before betting has closed on the event.

In its recent disclosure, the USTA said 19 courtsiders were "caught, removed and served trespass notices" in 2016. At least one courtsider was arrested last year.

And tennis is not alone.

Mounting evidence suggests other sports leagues may also be looking to implement the technology following the Supreme Court's decision in May to strike down the Professional and Amateur Sports Protection Act of 1992 (the federal sports betting ban), and allow states beyond Nevada to permit legalized sports wagering. Indeed, facial recognition cameras powered by artificial intelligence (AI) that tap into vast photo libraries can be an effective countermeasure in efforts to crack down on disfavored third parties who disseminate in-game data.

The USTA might even invite others to join forces with them.

"We remain open-minded about investigating economies of scale with other professional sports and law enforcement agencies related to enhanced enforcement of integrity strictures," the USTA wrote in its recent disclosure.

The use of facial recognition cameras even garnered a mention at last week's congressional hearing devoted to sports betting.

How prevalent will this technology be in the near future?

Tennis looks to make a move

Experts understand the impact facial recognition cameras can potentially have in tennis, while also acknowledging that the underlying integrity issue is nuanced.

"Extending the use of this technology to address and disrupt courtsiders is an understandable step," wrote Sportradar U.S. executive Laila Mintas in an email to ESPN. "However, courtsiders are different [than] match-fixers.

"Courtsiders are seeking to gain a latency advantage over betting operators (or other bettors on a betting exchange) by enabling bets on sports events before the betting operators adjust their prices based on live data feeds, whether official or unofficial. This is not match-fixing, but it is something that betting operators, sports leagues and data supply companies all have an interest in eliminating. The best way to do this is to use technology to deliver the highest quality and fastest data to as much of the global betting market as possible, thereby removing the latency advantage that courtsiders try to exploit and eventually putting them out of business."

The USTA has monetized real-time betting data since at least 2012.

"Currently, the USTA grants WME/IMG the rights to license live streaming and data for the US Open to the betting industry on a global basis as permitted by law," wrote the USTA in its disclosure to investigators.

To protect the commercial value of such sales, several "aggressive measures" and "additional resources" were adopted.

The USTA is "[w]orking with IMG to receive live courtsider detection based on and [sic] betting alerts and patterns at the U.S. Open," wrote the USTA in the same investigative disclosure.

As early as this past April, the USTA also moved to implement signage at select USTA professional tennis events putting spectators on notice about how photographs could potentially be used in crackdowns on the transmission of live scores for "commercial, betting, or gambling purposes."

"By entering the tournament grounds, spectators consent to the use of their voice, image, and/or likeness in any live or recorded video program, photograph or other transmission or reproduction of, or at, the tournament or any surrounding activities for any all [sic] purposes without further authorization or compensation," read one sign posted near an entrance to a tournament earlier this year.

First-person experience

Those on the front lines have had sneaking suspicions about high-tech cameras in tennis for years.

"We were worried about the facial recognition from 2012 onward," said Brad Hutchins, the author of "Game Set Cash! Inside the Secret World of International Tennis Trading," a recent book about live tennis betting. "They suddenly got so quick at catching us we assumed that had to be what was helping."

Hutchins, who has now retired from the activity, described some of the creative measures he and others took in response to the possible use of smart cameras at tournaments.

"I shaved my head once to try and avoid detection, although that's hardly going to stop facial recognition cameras." Brad Hutchins

"I shaved my head once to try and avoid detection, although that's hardly going to stop facial recognition cameras," Hutchins said. "But I do recall a few guys using fake mustaches and I wouldn't be surprised if there are other tactics being employed [now]."

Facial recognition cameras at tennis events can be used for purposes completely unrelated to sports betting, too.

Last year, PCMag.com reported that the USTA used the technology to "scan for any celebrities in the stands."

The USTA did not respond to multiple interview requests for this story to clarify if, or how, facial recognition technology was utilized this year.

Other leagues take note

Other sports leagues and event organizers appear to be following tennis' lead in looking to restrict access to the live data that power in-game wagering.

"We do not believe data companies should be allowed to enter sporting events under the guise of fans to commercially collect real-time data for use in betting," Major League Baseball executive Pat Courtney said in a statement to GamblingCompliance in March. In the immediate aftermath of the Supreme Court's May 14 ruling, NFL commissioner Roger Goodell took a similar stance, issuing a statement about the need to "protect our content and intellectual property from those who attempt to steal or misuse it."

Beyond the U.S., organizers of the Summer Olympic Games in Tokyo in 2020 have already announced plans to use facial recognition cameras capable of tracking everyone who enters the venues in Japan.

"By introducing the face recognition system, we hope to achieve high levels of safety, efficiency and smooth operation at security checkpoints before entry," Tokyo 2020 official Tsuyoshi Iwashita said in a statement last month.

The market to provide such services is heating up. Earlier this year, Sports Business Daily profiled six tech companies "in the face space" who market facial recognition software to the sports industry, many of whom have already entered into deals with individual teams and leagues.

Hints of potential concerns regarding accuracy

At least one research study has cast doubt on the accuracy of facial recognition cameras.

"Congress should press for a federal moratorium on the use of face surveillance until its harms, particularly to vulnerable communities, are fully considered," said an American Civil Liberties Union lawyer after the organization released results of a report in July that found a leading facial recognition program to have erroneously matched 28 members of Congress with police mugshots of unrelated people. A high rate of "false positives" also showed up in a recent test run involving British soccer, with more than 2,000 attendees at a Champions League match mistakenly labeled as potential criminals.

NBC News reported in July that facial recognition software "soon will be used to admit fans to Major League Baseball games." Thearon W. Henderson/Getty Images

Pushback has increased as facial recognition technology has crept into many facets of life, including law enforcement and school security measures. Both the Senate and House held congressional hearings on AI-related technologies in 2016. The congressional hearings came two years after the New York Times reported that the National Security Agency retained photographs obtained via facial recognition software.

Despite concerns, real-world examples appear to be increasing, such as the use of the technology in the immediate aftermath of this summer's mass shooting in Maryland that claimed the lives of five journalists.

"The suspect was uncooperative after apprehension, and the county police used facial recognition technology to identify him," reported The Atlantic in June.

Big picture of Big Brother in sports

Widespread use of face-tracking cameras -- with an assist from novels such as George Orwell's "1984" and movies such as "Minority Report," starring Tom Cruise -- has long conjured up thoughts of a dystopian totalitarian state.

The applications in sports appear more narrow, at least for now. For example, NBC News reported in July that facial recognition software "soon will be used to admit fans to Major League Baseball games."

According to former Nebraska attorney general Jon Bruning during testimony at last week's Congressional hearing about sports betting, the technology also can be used to identify problem gamblers, with casinos "looking at it via facial recognition."

Beyond that, the potential use of facial recognition cameras in the context of real-time sports betting is in its infancy. In the near-future, fans may see some new small print on the back of their tickets or increased in-stadium signage putting spectators on notice about transmitting up-to-the-second score updates. In contrast, other aspects may be shielded from view, as sports industry officials keep details close to the vest.

But in the coming years, as sports betting spreads beyond the five states where it is currently permitted, the use of facial recognition cameras will likely expand, along with debates about the use.

Regardless of the outcome, one thing is for certain: Those at the U.S. Open tennis tournament and other sporting events may never view the Kiss Cam the same way again.