Polygraphs are in the news once again after Christine Blasey Ford, now a 51-year-old professor in northern California, accused Trump's Supreme Court nominee Brett Kavanaugh of attempting to rape her when they were teenagers. According to Ford's account (which Kavanaugh denies), at a party in the early '80s, he and a friend took Ford into a room, turned up the music so no one could hear her protesting, pinned her to a bed, and tried to pull off her clothing. When she tried to scream, he allegedly put his hand over her mouth to shut her up.
Ford reportedly didn't tell anyone about the alleged attack until 2012, when she told a therapist, as well as her husband. After Kavanaugh was nominated for the Supreme Court, she contacted the Washington Post, as well as her congresswoman, Democrat Anna G. Eshoo, whose office then sent Ford's letter to the office of Sen. Dianne Feinstein, the ranking Democrat on the Judiciary Committee. That letter was later leaked to the press, and Ford's name then became public.
In early August, when Ford was still deciding whether or not to come forward, she took a polygraph test on the advice of her lawyer. That test was administered by a former FBI agent who concluded that she was not lying. Here's the thing, however: Polygraph tests are bullshit. That doesn't mean that Ford is lying, but the polygraph should not be a part of the equation in this or any other case.
The contemporary polygraph test was invented in the early 20th century. Then, as now, it measures the subject's physiological response under questioning. So, if a subject is asked he's ever cheated on his wife and his pulse spikes while he's insisting he hasn't, the thinking is, he's lying. Of course, he could also just be nervous, and decades of research have shown that the test just doesn't work. Not only can people be trained to pass polygraphs, the test can't distinguish between someone who is actually telling the truth and someone who just thinks they are telling the truth. It's a fundamental flaw that can't be fixed.
These days, polygraphs tests are rarely admissible in court, but that doesn't mean the police don't still use them, and there are numerous examples of people being wrongfully convicted due to the test; for instance, Jeff Deskovic, who was convicted of rape and murder after failing a polygraph as a teenager in 1990. Deskovic was exonerated in 2006, but by that time he'd spent 16 year in prison. Others have managed to get away with murder (literally) by manipulating lie detectors tests. Charlie Cullen, a New Jersey nurse, was suspected of murdering hundreds of patients at work but after he beat multiple polygraphs, investigators were thrown off the trail. Cullen went on to kill at least 39 more people before he was caught a decade later.
This isn't to say Christine Blasey Ford is lying. I'm inclined to think that she's not. But the polygraph should not be held of up as evidence of someone's innocence or guilt. The evidence says, it just doesn't work.