A murder trial judge has asked the jury to consider whether an 18-year-old drug dealer acted in self defence when he stabbed a Stevenage man who was part of a robbery which went drastically wrong.

Mark Altabas, 48, collapsed and died on April 21 last year after sustaining six stab wounds in his back after he tried to steal drugs from 18-year-old Destao Pedro – who is accused of his murder.

During the final day of Mr Pedro’s trial at London’s Old Bailey, His Honour Judge Martyn Zeidman QC summarised the prosecution case saying that Mr Altabas had met with two other cocaine addicts – Stuart Cuthbert, 49, of Knebworth and 36-year-old Chris Mooney from Stevenage – and smoked crack cocaine from pipes before they raided the house where Mr Pedro was staying in Long Leaves, Stevenage, in the early hours of the morning.

He said Mr Pedro had been living with 43-year-old Katie Holmes and Robert Crook, 53, at the address in an arrangement where he supplied them with drugs instead of paying rent.

Mr Pedro had travelled to London that day to visit friends and buy more drugs for £300, before returning to Stevenage where he sat in the living room of the house waiting for clients to arrive to buy some.

Judge Zeidman said the defence alleged that Mr Pedro had a knife by his side which he found comforting, ‘like a teddy bear’, and had been given to him by Mr Crook.

When the three robbers entered the house he said they had intended to ‘storm’ in, but couldn’t do so because a narrow hallway meant they had to enter in single file.

Mr Altabas had to go through a curtain to get into the front room where a struggle broke out between him and Mr Pedro.

The prosecution, he said, alleged Mr Pedro had deliberately stabbed Mr Altabas in the back six times.

He had, the prosecution argued, shouted ‘I will stab you’ and attacked Mr Altabas with force and intent – the blow that killed him being a deep wound.

This was supported by the fact that when first questioned by police Mr Pedro denied any knowledge of the incident, claiming the wounds had been sustained when he had been ‘stabbed by an Asian man’ and climbed out the bedroom window to escape.

But he later told the court it had been ‘stupid’ not to admit he had acted in self defence.

Judge Zeidman said the defence denied the murder charge saying Mr Altabas leapt on Mr Pedro and attacked him with a knife. Mr Pedro struggled to throw him off, ‘windmilling’ his arms in self defence.

During the struggle, Mr Pedro took a deep cut to his arm. He then came into contact with a knife on the floor and picked it up, continuing moving his arms in the same motion in self defence.

Mr Pedro, he said, didn’t dispute he may have caused injury to Mr Altabas, but didn’t accept he did it deliberately or unlawfully.

Judge Zeidman asked the jury to consider whether the wounds may have been inflicted in self defence or while Pedro had ‘lost self control’, both of which would mean he could not be convicted of murder.

After the robbers left, Mr Pedro allegedly asked Ms Holmes to clean the knife he had used and put on a second pair of jogging bottoms to cover up the blood stains on his trousers.

Judge Zeidman said Mr Mooney alleged Pedro had also lunged at him and stabbed him in the neck, so he shouted ‘get out’ and fled the house. He said Mr Altabas was last to leave, he collapsed once and got back up again, but couldn’t get into a getaway car.

But in an unusual step, Judge Zeidman warned the jury to take care with the evidence of the two robbers because of their previous ‘violent and cruel’ behaviour.

He said: “Each of them has appalling records and Mr Cuthbert has a previous conviction for lying in a murder trial for which he received 18 months in jail.

“There is no doubt that each of them had a propensity to act in a dishonest and violent manner.

“These are people who have an interest of their own to serve in co-operating with the police and in giving the evidence they gave.”

Mr Crook, who admitted he has been a heroin addict for 25 years and sells drugs to fund his addiction, is accused of conspiracy to rob. The prosecution says he helped arrange the robbery by making a series of phone calls to Mr Altabas, updating him on when Mr Pedro would be at home and what drugs he was likely to have available. His motivation was said to be that Mr Pedro owed him money.

Mr Crook denies the charge, claiming he liked Pedro and saw him as a ‘kind of son’ and that he only gave Mr Altabas information so he could buy drugs. He said he would never put Mr Pedro or Ms Holmes – who he loves – in that kind of danger.

Ms Holmes faces a charge of perverting the course of justice by tampering with evidence at the crime scene, including cleaning the knife used in the attack.

Judge Zeidman said her defence stated she left so many blood stains and other clues around the house that she had made virtually no attempt to cover up the crime and had no reason to suspect there would be a police investigation because at the time she had no idea that anyone had died.

The jury retired at 3.15pm yesterday to consider their verdict.