A mother sits in the examination room. Wires attached to her chest, fingers, and arm. The examiner asks simple questions. Is your name Susan? Yes. Do you live in Springfield? Yes. Did you kill your son? No. The machine does not believe her.

The polygraph measures physiological responses: heart rate, blood pressure, respiration, and skin conductivity. The theory is that lying produces stress that the body cannot hide. The mother's readings spiked on every question related to her son's death. She showed no reaction to neutral questions. The examiner noted deception indicated. The mother maintained her innocence for another year. Then her boyfriend confessed that she had smothered the child while he watched. The polygraph was not admissible in court. But it gave detectives the confidence to keep digging. They found the text messages. They found the internet searches. They found the life insurance policy taken out weeks before the death. The mother pleaded guilty to second-degree murder. She is serving twenty-five years.

Turn down the lights, put on your headphones, and press play because the machine does not care if you are a mother. It only cares if you are lying.

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