Results from the Brain Electrical Oscillations Signature (BEOS) test are now accepted in Indian courts of law. This past summer, a woman was convicted of murder largely because of brain scan results.
The woman, Aditi Sharma, was accused of killing her former fiancé, Udit Bharati. They were living in Pune when Ms. Sharma met another man and eloped with him to Delhi. Later Ms. Sharma returned to Pune and, according to prosecutors, asked Mr. Bharati to meet her at a McDonald’s. She was accused of poisoning him with arsenic-laced food.
Ms. Sharma, 24, agreed to take a BEOS test in Mumbai, the capital of Maharashtra. (Suspects may be tested only with their consent, but forensic investigators say many agree because they assume it will spare them an aggressive police interrogation.)
After placing 32 electrodes on Ms. Sharma’s head, investigators said, they read aloud their version of events, speaking in the first person (“I bought arsenic”; “I met Udit at McDonald’s”), along with neutral statements like “The sky is blue,” which help the software distinguish memories from normal cognition.
For an hour, Ms. Sharma said nothing. But the relevant nooks of her brain where memories are thought to be stored buzzed when the crime was recounted, according to Mr. Joseph, the state investigator. The judge endorsed Mr. Joseph’s assertion that the scans were proof of “experiential knowledge” of having committed the murder, rather than just having heard about it.
In the U.S., the results from lie detectors is not admissible in courts; the National Academy of Sciences states "Almost a century of research in scientific psychology and physiology provides little basis for the expectation that a polygraph test could have extremely high accuracy..."
However, a variety of recent advances in neurological research has lead scientists (and entrepreneurs) to believe that some sort of device could be used to find the truth in a person's brain state.
Science fiction fans may recall the highly visual veridicator from H. Beam Piper's 1962 novel Little Fuzzy. Robert Heinlein had a go at the idea in his 1954 novel The Star Beast:
"Mrs. Donahue, tell us what happened."
She sniffed. " Well! I was lying down, trying to snatch a few minutes rest; I have so many responsibilities, clubs and charitable committees and things.
Greenberg was watching the truth meter over her head. The needle wobble restlessly, but did not kick over into the red enough to set off the warning buzzer...
(Read more about the truth meter)
The first work on the idea of a lie detector was done by William Moulton Marston during WWI; he worked on a systolic blood-pressure test that could be used to detect deception.
He also created an illustrated version of a special handheld lie detector in a well-known fictional work; see a brief video of this device in action.
(The original handheld lie detector)
The Lasso of Truth compels a person lassoed to tell the truth - in the Wonder Woman comic series.
According to an article in the New York Times, U.S. psychologists and neuroscientists have called the use of the Brain Electrical Oscillations Signature test in court “fascinating,” “ridiculous,” “chilling” and “unconscionable.” In the meantime, Ms. Sharma maintains her innocence.