Your next video call might include an invisible polygraph examiner. Google and competitors are racing to deploy AI systems that promise to catch lies through voice patterns, facial microexpressions, and language analysis. The pitch sounds compelling: revolutionary accuracy in detecting deception, finally replacing those notoriously unreliable polygraph machines. The reality is more sobering. Peer-reviewed research consistently shows multimodal AI lie detection maxing out around 75-79% accuracy in controlled settings-impressive, but nowhere near the bold marketing claims circulating in tech circles.