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.
