Twenty-seven anti-depressant pills slipped into the beer of a hard-drinking dwarf could have alone led to his death, a court heard.

A sleep disorder expert said there had been other cases of people dying from such a dose of Mirtazapine. “In fact, lower doses have been associated with fatality,” added Dr Irshaad Ebrahim.

The combination of the tablets, excessive alcohol and a sleep condition, he said, would have been lethal to Jason Wood.

Dr Ebrahim, director of the London Sleep Centre, told a jury Mr Wood’s size - 4ft tall and weighing six stone - would also have had a bearing on his death.

“This dose would have more of an impact on him per kilogramme of his weight,” he explained. “At around 40kg, he was the size of an 11 or 12-year-old.”

Maidstone Crown Court has heard Mr Wood, 30, had been drinking for several days at a house in Camden Square, Ramsgate, when Webster, 26, put the pills in his beer can “for a laugh” in October last year.

He was found slumped in an armchair within three hours and declared dead at the scene. His alcohol level was almost three times the legal driving limit.

Dr Ebrahim said he had prescribed Mirtazapine to thousands of patients since it was launched almost 20 years ago.

“It is a relatively safe drug,” he said. “The major problem with older anti-depressants was that they were unsafe in overdose.

“Mirtazapine in overdose can also cause problems and has been known to cause death, but much less frequently than older anti-depressants.”

Dr Ebrahim said the Mirtazapine and alcohol in Mr Wood’s body were both in the toxic range. The Mirtazapine was 12 to 13 times the therapeutic dose.

One juror asked the question: “What minimum dose of Mirtazapine would be fatal to a person of Jason’s body and size and weight?”

The expert replied: “Body size and weight would have a bearing on it because it is done per kilogramme.”

“On the night in question, the only thing that was significantly different was the fact he had a very high toxic level of Mirtazapine. It is a very strong sedative" - Dr Irshaad Ebrahim

Mr Wood had been a heavy drinker since the age of 18 and also had moderate sleep apnoea, which caused difficulty in breathing. He had been given an oxygen mask to use at night but did not wear it.

“It would allow him to breathe normally in sleep,” said Dr Ebrahim. “It would eliminate his snoring.”

He continued: “On the night in question, the only thing that was significantly different was the fact he had a very high toxic level of Mirtazapine. It is a very strong sedative.

“That is why it is given at night to patients who have a problem sleeping. High doses can be as sedative, like alcohol is a sedative.

“Jason was over-sedated possibly to the level of being in a coma. That combination most likely led to his death.”

Dr Ebrahim accepted it was “a possibility” Mr Wood could have died exclusively from sleep apnoea and alcohol consumption.

Webster, of Dover Road East, Gravesend, denies manslaughter and an alternative charge of administering poison or noxious substance as to endanger life.

The trial continues.