What GAO Found

The Transportation Security Administration (TSA) does not have valid evidence that most of the revised behavioral indicators (28 of 36) used in its behavior detection activities can be used to identify individuals who may pose a threat to aviation security. GAO defined valid evidence as original research that meets generally accepted research standards and presents evidence that is applicable in supporting the specific behavioral indicators in TSA's revised list. Original research sources presenting valid evidence are important because the data and conclusions they present are derived from empirical research that can be replicated and evaluated. In GAO's review of all 178 sources TSA cited as support for its revised list, GAO found that 98 percent (175 of 178) of the sources do not provide valid evidence that is applicable to the specific behavioral indicators TSA cited them as supporting. Specifically,

• Seventy-seven percent of the sources TSA cited (137 of 178) are news articles, opinion pieces, presentations created by law enforcement entities and industry groups, and screen shots of online medical websites that do not meet GAO's definition of valid evidence. 

• Twelve percent of the sources TSA cited (21 of 178) are journal articles, books reviewing existing literature, and other publications that may reference original research in the text, but do not themselves present original analysis, methods, or data whose reliability and validity can be assessed. 

• Eleven percent of the sources TSA cited (20 of 178) are original research sources reporting original data and methods. However, 5 of these sources do not meet generally accepted research standards. Of the 15 sources that meet generally accepted research standards, 12 do not present information and conclusions that are applicable to the specific behavioral indicators TSA cited these sources as supporting. 

In total, GAO found that 3 of the 178 total sources cited could be used as valid evidence to support 8 of the 36 behavioral indicators in TSA's revised list. More specifically, TSA has one source of valid evidence to support each of 7 indicators, 2 sources of valid evidence to support 1 indicator, and does not have valid evidence to support 28 behavioral indicators. GAO makes no new recommendations in this report.

Why GAO Did This Study

Over the past 10 years, TSA has employed thousands of trained behavior detection officers to identify passengers exhibiting behaviors indicative of stress, fear, or deception at airport screening checkpoints. According to TSA, certain verbal and nonverbal cues and behaviors--TSA's behavioral indicators--may indicate mal-intent, such as the intent to carry out a terrorist attack, and provide a means for TSA to identify passengers who may pose a risk to aviation security and refer them for additional screening. These behavioral indicators include, for example, assessing the way an individual swallows or the degree to which an individual's eyes are open. GAO reported in November 2013 that available evidence did not support whether behavioral indicators can be used to identify persons who may pose a risk to aviation security and recommended that TSA limit future funding for the agency's behavior detection activities until TSA can provide such scientifically validated evidence. Since GAO's 2013 report, TSA has reduced funding for its behavior detection activities, revised and shortened its list of behavioral indicators, and taken steps to identify additional evidence to support its indicators.

GAO was asked to review the steps TSA has taken in response to GAO's recommendation. This report assesses the extent to which TSA has valid evidence demonstrating that its revised list of behavioral indicators can be used to identify passengers who pose a threat to aviation security. GAO reviewed and categorized all 178 sources that, as of April 2017, TSA cited as providing support for specific behavioral indicators to identify the extent to which they present valid evidence. GAO also interviewed TSA officials and officials from the American Institutes for Research--a behavioral and social science research and evaluation organization--and analyzed documentary evidence from these entities to better understand the steps TSA has taken and evidence TSA has used to substantiate its revised list of behavioral indicators.

What GAO Recommends 

GAO makes no new recommendations in this report.

For more information, contact Nancy Kingsbury at (202) 512-2700 or kingsburyn@gao.gov and Jenny Grover at (202) 512-7141 or groverj@gao.gov.

• View Report (PDF)