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What’s the straight dope on truth serums? What are they? What exactly do they do? Do sodium pentothal and the like really make witnesses spill their guts? If so, why don’t we use it for courtrooms and police interrogations? Please hurry, my suspect is wrestling his way out of the handcuffs. —J.F.

Truth serums are based on a phenomenon known since ancient times, when Pliny the Elder coined the phrase in vino veritas: “in wine, truth.” He meant anything that lowers your inhibitions is likely to cause you to say things you’d normally keep secret. Unfortunately for cops and CIA interrogators, what you spill isn’t necessarily the truth.

People have been plying one another with liquor for centuries, but the earliest confession induced using something stronger was reported in a 1903 criminal case involving a New York cop. He admitted under ether he’d faked insanity when accused of killing his wife.

The first drug to catch on as a truth serum was scopolamine, a depressant and sleeping agent. Mixed with morphine, it was used to put women in labor into a “twilight sleep” so they’d forget the pain. To gauge the dose, the doctor would ask the patient questions until she could no longer remember anything. The pioneer of truth serum research, a Texas obstetrician named Robert House, claimed his patients always answered truthfully, and from this concluded the drug left them unable to lie. In 1922 he tried the technique on two prisoners in a Dallas jail, helping to exonerate both.

Although truth serum caught the fancy of reporters and some scientists, it was never widely accepted as a way of extracting criminal confessions. Several sensational early cases produced a variety of results. In 1924, five black men in Birmingham, Ala., reportedly confessed under the influence of an unspecified truth serum to eight ax murders, then confirmed their guilt after the drug had worn off. A few years later a chauffeur in Hawaii confessed under scopolamine to writing the note in a kidnap-murder case but repudiated his statement afterward; ultimately the crime was pinned on someone else.

By the mid-1930s, scopolamine had been largely abandoned in favor of safer drugs such as sodium amytal and sodium thiopental. But the theory stayed the same: Once you’re in a trance and have thus lost the complex brain functions needed to sustain a lie, you’re reduced to telling the truth.

The problem with truth serums is the results can’t be depended on. It’s easy to find case reports of people recounting detailed stories under the influence of drugs of which they have no recollection afterward—and the stories check out. But researchers know of just as many confessions that were demonstrably false.

During World War II, the forerunner to the CIA, tried using cannabis extract to make people talk. Later generations of spies wondered whether they could get results with mescaline and LSD. In the 1950s the CIA launched a covert research program called MK-Ultra to explore the possibilities of truth serums and behavior-modification drugs. The project gained notoriety after one participant jumped out a hotel window while on LSD.

The U.S. Supreme Court has ruled that confessions obtained using drugs are inadmissible as evidence. The European Court of Human Rights has likewise prohibited the practice. Nonetheless, drugs continue to be used to extract confessions in some parts of the world.

Though I don’t make light of ethical considerations, the argument likely to carry more weight in these nervous times is the practical one. Let’s say out of 100 bits of data forcibly extracted using drugs or other means, five are legitimate. How do you know which five? —Cecil Adams

Is there something you need to get straight? Take it up with Cecil at straightdope.com.