A real-life forensic psychiatrist has shared what it's like to look into the minds of the world's scariest killers - and what TV always gets wrong.
Dr Sohom Das, 43, has spent the last 11 years working with notorious killers, visiting them while behind bars or in mental institutions like Broadmoor.
His job as an expert witness is to assess whether they have a mental illness, if it affected their criminal responsibility, and whether they should be sent to prison or a psychiatric hospital.
Despite the profession being sensationalized in popular TV shows and films, including Habbial Lector from The Silence of the Lambs, Dr Das said that there are several misconceptions and what we see on the big screen is rarely correct.
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He said: "I think there are a lot of misconceptions on TV. One thing is that there seems to be this belief that forensic psychiatrists solve crimes or catch criminals but we have nothing to do with that.
"We assess them after they've been caught. We assess whether they have a mental illness, and if they do, what specific symptoms were they suffering at the time of the crime and whether they drove the offence. If so, if they should go to a psychiatric hospital or to prison instead.
"Some people make a career out of criminal profiling but I think it's a pseudoscience. It's based on the premise that all criminals act in a predictable manner which isn't always true."
Another common trope is where violent criminals rely on a plea of insanity to spare them jail time, such as with McMurphy in One Flew Over the Cuckoo's Nest.
Dr Das continued: "I see a lot of people, one every two or three months, where I'm convinced the defendant is either faking or exaggerating their condition to reduce culpability.
"You take it on a case by case basis, but usually it's quite easy to see when people are faking mental illness.
"If people tell me they're hearing voices and can't function, but they've got no signs and there is no evidence of this in their medical records then I become suspicious.
"I've assessed defendants who have stabbed people in the pub then claimed they've had a moment of psychosis, like hearing voices, but witnesses say they were just drunk and acting violently.
"The way I tell is by looking at all the evidence, to see how they're acting after the offence. If prison officers say they are isolated or paranoid, they may be psychotic.
"Generally speaking, if someone is genuinely psychotic and hearing voices, they are very guarded and dismissive of me. I'm someone they've never met before and they won't open up to me. Whereas someone who is faking it has an agenda.
"People who try to fake mental illness like psychosis usually overact. They emulate the depictions they have seen on TV, which is inaccurate. They tend to overegg it.
"Psychosis is often misunderstood. The main symptoms are hallucinations and delusions.
"Hallucinations are where people hear voices. If someone says they are hearing voices in their head, usually that doesn't indicate psychosis - you would hear it outside your head. They sound like they're coming from the room, and can sound very realistic.
"And paranoid delusions include when the sufferer believes that people are following them, or want to hurt them, or have planted microphones around the place."
Dr Das recalled one case where he was faced with the dilemma of assessing whether a murder suspect was faking their mental health condition, or had genuinely suffered from a psychotic break.
To protect his client, the name has been changed to Yasmine. She had murdered a family member and had delusional beliefs that they were full of demons, and that she could later resurrect them.
He continued: "I gave evidence for the murder trial at the Old Bailey, for the 18-year-old school girl who had killed her two-year-old nephew in a flash of psychosis.
"The reason why this case was so unusual was that she didn't have any history of violence or problems with her mental health.
"Yasmine was exceptional as she had no signs of prior psychosis. A few weeks before the killing, she was making comments about seeing her soul in the clouds and started listening to weird instrumental music. However, there was no clear indication that she would do something as extreme as she did.
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"She believed her nephew had these demons inside of him so she smothered him and killed him. It was a really horrendous event.
"Her mother came home and called the police. Meanwhile, Yasmin was saying she believed she could reincarnate the young boy.
"What stands out for me was that she was very hard to assess as she was uncooperative. It was a challenge to give evidence in her murder trial, as I only had suspicions that she was psychotic.
"We medicated her until her delusional beliefs stopped, and I think reality finally sank into her psyche. Until that point, she believed she was right and everyone else was wrong. She had realised the impact of her actions. Then we had to treat her depression with other medications."
Dr Sohom Das, 43, is a consultant forensic psychiatrist, based in north London, and is the author of ‘In Two Minds: stories of murder, justice, and recovery from a forensic psychiatrist’, which came out in March and the host of a YouTube channel, ‘A Psych for Sore Minds’
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