Truth to power
The narco-analysis test is conducted by injecting three grams of sodium pentothal dissolved in water, designed to push the suspect towards a hypnotic twilight state where they are questioned several times over to tease out ambiguities. Brain-mapping and lie-detection also measure physiological responses to stimuli as indication of psychological states. Lie detectors have been around in various versions since the '20s, when they were called "the soul machines" or "machines for the cure of liars". Meanwhile, "truth serums", used on World War II spy suspects in the US, had been struck down as unconstitutional, as far back as 1963.
Either way, confessions sweated out through these methods are not admissible as evidence in court. But they were often used to find and chase up on leads — they have been notably administered on Ajmal Kasab and in the Nithari murder case. Now, those options are less easily available to investigating agencies — which might detract from their efficiency somewhat, but is undoubtedly a reminder that no matter how exigent the circumstances, dodgy science should not be put to the service of an elusive justice. Many studies have shown that persons who have been administered these chemicals can often repeat the interrogators' words and cues or freely fantasise.