Slow to change

In the US, though, such science-based reforms have yet to make significant inroads among police and other security officials. The US Department of Homeland Security’s Transportation Security Administration, for example, still uses nonverbal deception clues to screen airport passengers for questioning. The agency’s secretive behavioral screening checklist instructs agents to look for supposed liars’ tells such as averted gaze — considered a sign of respect in some cultures — and prolonged stare, rapid blinking, complaining, whistling, exaggerated yawning, covering the mouth while speaking and excessive fidgeting or personal grooming. All have been thoroughly debunked by researchers.

With agents relying on such vague, contradictory grounds for suspicion, it’s perhaps not surprising that passengers lodged 2,251 formal complaints between 2015 and 2018 claiming that they’d been profiled based on nationality, race, ethnicity or other reasons. Congressional scrutiny of TSA airport screening methods goes back to 2013, when the US Government Accountability Office — an arm of Congress that audits, evaluates and advises on government programs — reviewed the scientific evidence for behavioral detection and found it lacking, recommending that the TSA limit funding and curtail its use. In response, the TSA eliminated the use of stand-alone behavior detection officers and reduced the checklist from 94 to 36 indicators, but retained many scientifically unsupported elements like heavy sweating.

An officer of the US Transportation Security Administration watches travelers at an airport. The agency still uses behavioral indicators to pick out suspicious people, even though this has little scientific basis. Credit: Scott Olson/Getty Images

In response to renewed Congressional scrutiny, the TSA in 2019 promised to improve staff supervision to reduce profiling. Still, the agency continues to see the value of behavioral screening. As a Homeland Security official told congressional investigators, “common sense” behavioral indicators are worth including in a “rational and defensible security program” even if they do not meet academic standards of scientific evidence. In a statement to Knowable, TSA media relations manager R. Carter Langston said that “TSA believes behavioral detection provides a critical and effective layer of security within the nation’s transportation system.” The TSA points to two separate behavioral detection successes in the last 11 years that prevented three passengers from boarding airplanes with explosive or incendiary devices.

But, says Mann, without knowing how many would-be terrorists slipped through security undetected, the success of such a program cannot be measured. And, in fact, in 2015 the acting head of the TSA was reassigned after Homeland Security undercover agents in an internal investigation successfully smuggled fake explosive devices and real weapons through airport security 95 percent of the time.

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In 2019, Mann, Hartwig and 49 other university researchers published a review evaluating the evidence for behavioral analysis screening, concluding that law enforcement professionals should abandon this “fundamentally misguided” pseudoscience, which may “harm the life and liberty of individuals.”

Hartwig, meanwhile, has teamed with national security expert Mark Fallon, a former special agent with the US Naval Criminal Investigative Service and former Homeland Security assistant director, to create a new training curriculum for investigators that is more firmly based in science. “Progress has been slow,” Fallon says. But he hopes that future reforms may save people from the sort of unjust convictions that marred the lives of Jeffrey Deskovic and Marty Tankleff.

For Tankleff, stereotypes about liars have proved tenacious. In his years-long campaign to win exoneration and recently to practice law, the reserved, bookish man had to learn to show more feeling “to create a new narrative” of wronged innocence, says Lonnie Soury, a crisis manager who coached him in the effort. It worked, and Tankleff finally won admittance to the New York bar in 2020. Why was showing emotion so critical? “People,” says Soury, “are very biased.”