A vulnerable prisoner who died unexpectedly in his cell had medical reports missing from his file, an inquest heard.

The standard of record keeping at Wandsworth prison’s substance misuse unit was criticised by a jury at Westminster Coroner’s Court, who spent four days listening to the events surrounding the death of 38-year-old prisoner and detox patient, Scott Marriott.

Last Thursday, members of the jury returned a narrative verdict into the former painter and decorator’s death – prompting some of his relatives to walk out of the court in tears.

Afterwards, Mr Marriott’s uncle said the family was “disappointed” with the outcome, but declined to comment further.

Over the course of the jury inquest – a hearing used when deaths happen in prison – the court was told Mr Marriott, whose funeral was attended by more than 200 friends and family members, was undergoing a drug and alcohol detox when he was found dead on September 17, 2009.

After his arrival at the Heathfield Road prison on September 12, Mr Marriott told medical staff he smoked heroin and drank eight to 10 cans of strong cider a day.

In the days that followed he was given regular doses of chlordiazepoxide, to manage acute alcohol withdrawal syndrome, and methadone, which aids opiate withdrawal.

He was also prescribed insomnia medication zopiclone after he complained about having trouble sleeping.

The day before he was found in his cell “discoloured with no pulse” by prison officer, Paul Murphy, Mr Marriott’s mum Wendy visited him.

She told the court: “He kept yawning and his eyes kept going back in his head and rolling up.”

He complained of seeing his girlfriend’s cat during hallucinations and suspected his physical and mental state might have been affected by the drugs he had been prescribed.

According to the Deputy Coroner Shirley Radcliffe, expert witness ZubairChaudhry, a doctor based at Feltham young offender institution, admitted a “double detox is always risky and requires close monitoring”.

He agreed with other medical experts that Mr Marriott’s death could have come about due to the synergetic effects of the medication without signs of toxicity being displayed.

However, Dr Chaudhry raised concern that medical files detailing Mr Marriott’s treatment were missing and said he would like to have seen daily blood pressure recordings.

The Marriott’s family solicitor, Nick Brown, asked medical staff who gave evidence whether guidelines about monitoring detox patients were not being followed.

But staff insisted duties were carried out under an established and medically approved system.

The jury ruled Mr Marriott died due to mixed drug toxicity, and found the drugs he was given to have been prescribed within national guidelines and deeming the level of monitoring he was given to be “appropriate”.

The foreman added: “The jury finds that some aspects of the record keeping in relation to treatment was inadequate, however, the jury find this did not contribute to his death.”