Everything began to unravel for Christopher Watts after he failed a polygraph (“lie detector”) test during police questioning in August 2018. Watts would soon after confess to the murder of his wife, Shanann Watts, and their two daughters, Bella and Celeste. In November of that year, Watts was given three consecutive life sentences. He is currently serving out those sentences at a maximum-security prison in Wisconsin.
Viewers of the Netflix documentary about the case, American Murder, which uses only police body camera footage, interrogation footage, and social media accounts to tell the story, will probably wonder why Watts agreed to the polygraph examination in the first place. Did he think he could beat it?
2018 saw another famous polygraph contention when Democrats called for then Supreme Court nominee Brett Kavanaugh to take the test following sexual assault allegations by Christine Blasey Ford. (Ford herself took the polygraph test, the answers for which were deemed “not indicative of deception,” i.e., she passed.) Kavanaugh said the tests were unreliable, and he did not take one.
Polygraph tests and their efficacy are common crime fiction tropes—where we see sly criminals beating the test by controlling their heartrate and breathing. Perhaps Watts thought he too could beat the test if he just remained calm. Of course, he did not. That is, remain calm or pass the test.
But do the tests always work as intended?
Do polygraph tests work?
Polygraph tests measure bodily responses such as blood pressure, heartrate, breathing, and even perspiration. Changes in these physiological signs are believed to indicate when an individual is being untruthful. Basically, they measure stress and anxiety.
But some experts question this underlying premise—that liars will necessarily show signs of stress while innocent test takers will not. In a report by the National Research Council, researchers concluded that “the basic science relevant to the polygraph suggests that it can at best be an imperfect instrument, but it leaves unclear the degree of imperfection.”
If the test is not properly administered, experts say, one can also run into higher inaccuracies. So too if the test takers have autonomic disorders or are on certain medications.
Professor Donald Grubin of New Castle University has conducted further research on polygraph examinations. Though he also saw several ways in which the test could be inaccurate, he noted in an interview with the BBC that “if the examiner is well-trained, if the test is properly carried out, and if there’s proper quality controls, the accuracy is estimated between 80-90 percent.” Still, Grubin noted that with proper training an individual could beat the test.
Still, there are a host of problems with using the test, especially in a narrow criminal justice setting.
Chris Watts might have refused to take the test on these grounds, citing potential inaccuracies. But the very thing the test is meant to measure—anxiety—was already fully apparent to investigators.
In this case, the polygraph examination proved to be a better incentive for confession than a standalone indictment of guilt.
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