India's Supreme Court has determined that a "truth" drug and other investigative techniques used in police questioning are illegal.
"Narco, brain mapping and polygraph tests are illegal and a violation of personal liberty," the court declared in its ruling Wednesday.
The "truth" drug, sodium penthanol, is injected into suspects for interrogations in the belief it inhibits a person's ability to lie. But the court ruled against its use, even if a suspect consents to the "truth" test, and said it cannot be used as evidence.
"From the scientific evidence that's available, even after administering a narco test, the suspect has the capacity to lie. So it puts a big question mark on the reliability of the test and the evidence gathered on the basis of it," Ayaz Khan, a criminal lawyer based in Mumbai, told ABC News.
The prevalence and necessity of narco testing is disputed throughout the law enforcement community. Many say it's a technique frequently used by investigators, but Khan said it is contained to high profile cases when no other interrogation option is available. Still, Khan said it is barbaric.
"It's indeed a torture. Moreover, no person can be compelled to be a witness against himself. And the narco test exactly does that. So the court has rightly ruled that it's unconstitutional and unwarranted intrusion of personal liberty," Khan said.
Indian police have a reputation for using unnecessarily brutal force, though the image is more frightening than the reality, especially as media has drawn attention to the issue, according to Ved Marwah, former Delhi police chief.
Marwah told ABC News that the problems within the police force are much deeper than outright aggression. And the administration of a "truth" drug - while it can be a helpful tool - is not a magic bullet to solving crimes. Fixing the long-standing problems within the police could prove far more helpful long-term.
"The ban won't make it difficult, but will present a new challenge to think of other legal ways to solve the crime puzzle. And I am sure Indian police will live up to the challenge," Marwah said. "The real problem is getting quality officers and improving their living and working conditions, which is pathetic at present."
He added that the ban will not necessarily hamper future investigations.
"Narco is just an aid to investigation which works on hypothesis. It just gives a lead. Evidence culled from Narco test was not admissible earlier as well. So, the verdict of the court will only change the dynamics of investigations. The officers will now have to look for other cues and leads.
Another tool now banned is the Brain Electrical Activation Profile (BEAP), also known as brain mapping. The technique which analyzes brain waves is still not used frequently.
"It's not effective," Khan said. "There's still a question mark over its credibility."