CLAIMS that a drug used to treat depression could have caused a son to murder his mother have been described as “extremely unlikely” by a pharmacology expert.

Professor David Taylor told a jury at Manchester Crown Court that Sertraline is regarded as being so safe that the UK Aviation Authority allows pilots to fly while taking it.

Paul Stones, who is on trial, accused of murdering his mother, 58-year-old Marian Stones at the home they shared in Park Terrace, Eagley, told the court he has only brief memories of strangling his mother on June 9, last year. He believes Sertraline, the anti-depressant he had been taking for three-and-a-half years, caused his aggression, which he alleges was out of character.

Giving evidence in his defence Stones, aged 38, explained he had forgotten to take his daily dose on the Wednesday and Thursday before the attack, consuming a triple dose on Friday, the day before he strangled Ms Stones.

Last week clinical pharmacologist Dr Andrew Herxheimer told the court he believes the increased dose, combined with alcohol and Stones’ emotional state on the night of the killing, had led to an “abnormality of mental functioning”.

He added that the group of drugs known as SSRIs, (selective serotonin reuptake inhibitors) of which Sertraline is one, have been associated with aggression in patients and a reduction in impulse control.

But yesterday the claims were refuted by Professor Taylor, who stated that no direct causal link has ever been made between the drugs and violent behaviour and stressed that, in the Netherlands where there was an increase in the prescribing of SSRIs, the homicide rates actually came down.

There have been reports that some patients can suffer agitation as a side effect of the drug, but Professor Taylor added that this would have emerged in Stones within weeks of it first being prescribed to him.

He stressed that, although there is no definite proof, there is only a “remote” possibility that Sertraline could have caused Stones to behave violently.

“I think it is extremely unlikely there is an association,” he added.

The case continues.