They're a joke according to basically every psychologist and criminal justice expert. The statistical evidence that they're ridiculously faulty is overwhelming, and the logical reason behind it is clear-cut. They can't tell what you're nervous about, only that you're nervous. Meaning sociopaths who feel no shame get off scot-free, and people who are anxious at being accused are read as guilty.

That they're still in such widespread use is baffling. It just shows how reticent ossified organizations are to change methods that they've grown to trust and depend on. Even if it's the equivalent of making life decisions based on palm-reading.