Armed police were last night at the bedside of Deith Bridges, 21, who was shot in the leg and chest by two men in a car as he left a pub in Ruislip, north-west London.
He has been accused of being part of a conspiracy to murder businessman Graeme Woodhatch, who was shot dead by a woman while making a telephone call in hospital.
The latest shooting occurred on the day that Te Rangimaria Ngarimu - who has admitted murdering Mr Woodhatch - was due to give evidence.
Mr Bridges was on bail and staying in the Ruislip area during the trial. His co-accused, Paul Tubbs, has had his bail withdrawn and is being held in custody for his own protection.
A Scotland Yard spokesman said they were considering whether the incident was connected to the trial. Officers were concentrating their inquiries in the Ruislip area but have not ruled out questioning former associates of Mr Woodhatch. The spokesman refused to say whether extra security would be given to the jury or other defendants.
Mr Bridges was shot from behind as he returned home along Queen's Walk at 12.55am yesterday after drinking at the Clay Pigeon pub. Two men called his name and shot him with a .22 semi-automatic. Residents heard Mr Bridges screaming and called the police.
One witness said: 'He was covered in blood. Apparently he had been shot through the leg and the bullet had passed straight through. He had also been shot twice in the chest. He looked very bad and was in a complete state of panic.'
Mr Bridges was taken to Hillingdon hospital where he had surgery to remove a bullet lodged near his heart. His condition was said to be serious but not life-threatening.
There were gasps of shock from the jury as the judge, the Recorder of London, Sir Lawrence Verney QC, told them of the attack. The trial was postponed until Monday.
The trial of Mr Bridges, 22, of Chapeltown, Leeds, and Mr Tubbs, 35, of Enfield, north London, began on Wednesday. They are accused of conspiracy to murder and perverting the course of justice by disposing of a gun. They deny all charges.
The court was told that they plotted together to kill Mr Woodhatch, 38, a roofing contractor who had cheated both men out of money.
Nicholas Atkinson QC, prosecuting, said Mr Bridges hired as the killer his friend Ngarimu, a 28-year-old student and barmaid. Mr Bridges provided the gun and Mr Tubbs was to pay her pounds 7,000 for the murder, he said.
Ngarimu, who has admitted the murder, went to the Royal Free Hospital, London, on 24 May where Mr Woodhatch was recovering from an operation. She shot him in the face, head and shoulder.
The trial continues.