An inquest jury has ruled that a former public schoolboy detained after taking a "legal high" died from a cardiac arrest after he was found in his police cell in Yeovil.
James Herbert, 25, died almost three years ago after he was held under the Mental Health Act by Avon and Somerset Police.
Mr Herbert, who started smoking cannabis as a teenager and also took cocaine, ketamine, ecstasy and LSD, had taken the NRG-1 drug when he was seen acting strangely in Bath Road, Wells, Somerset on the evening of June 10, 2010.
He was restrained by police, placed in the back of a patrol van and driven more than 27 miles to Yeovil police station before being carried on a blanket into a cell, where he was left on the floor naked.
Mr Herbert was later found to be unresponsive and was taken to Yeovil District Hospital by ambulance where he was declared dead.
Following a three-week hearing at Wells Town Hall where an inquest jury heard from 34 witnesses and saw 30 written statements, a narrative verdict was returned by the panel.
The jury also highlighted factors that may have contributed to Mr Herbert's death, such as the lack of communication between police officers about Mr Herbert's mental health, drug use and previous incidents; the failure to call for medical assistance while he was being taken to the police station; and the need for closer monitoring of him during that journey.
East Somerset Coroner Tony Williams said he would be writing to the chief constable of Avon and Somerset Police to highlight those issues raised by the jury.
Speaking after the verdict, Mr Herbert's parents, Tony Herbert and Barbara Montgomery, criticised the police.