A lawyer representing the family of MI6 spy Gareth Williams whose body was found in a holdall has suggested the secret services may have been involved in his death.
Anthony O'Toole, the Williams' family lawyer, made the accusation in open court during the 31-year-old GCHQ code breaker's inquest at Westminster Coroner's Court.
The allegation came after it emerged MI6 failed to hand over nine computer memory sticks to Scotland Yard.
A black North Face holdall - similar to the one which Mr Williams was found dead in at his flat - was eventually passed to police.
The Metropolitan Police team investigating Mr William's death did not have direct access to his office.
Instead, the force's counter-terror SO15 branch, which has specialist security clearance, acted as a conduit between MI6 and the investigation team.
Two officers from the SO15 unit - Superintendent Michael Broster and Detective Constable Colin Hall - searched Mr Williams' MI6 office.
They only took three items - his phone, some notes and a copy of his birth certificate.
Asked why he did not take the memory sticks, Supt Broster said he did not think they were relevant - and admitted MI6 were left to examine them.
Mr O'Toole said: "So if the person who killed Gareth Williams was a member of SIS (MI6) you would do nothing to investigate because you believed that organisation to be trustworthy?"
Supt Broster insisted MI6 had been fully co-operative.
The officer was also criticised by Coroner Fiona Wilcox, who told him he was offering "total non-sequitur" reasons for failing to pass on evidence.
"I suggest that this means you have not been completely impartial in this case," she said.
Mr O'Toole also accused DC Hall of failing to take the probe seriously.
"If this had not involved SIS and it was the Kray twins you were investigating, you would have gone into this in far more detail," he told the officer.
Members of Mr Williams' family shook their heads as DC Hall revealed his search of Mr Williams' office was called off shortly after the spy was found dead.
Mr Hall said "there was stuff in there of a sensitive nature" in the bag but, when asked what, he said he could not remember.
Mr O'Toole added: "That's about as helpful as a London pea souper."
Earlier, Detective Chief Inspector Jackie Sebire, the police officer in charge of the investigation, returned to give evidence to the inquest and told the coroner she had no knowledge of the memory sticks, or the bag, until this morning.
"Had I known about their existence, I would have expected them to be disclosed and any relevant information to be sent to my team," she said.
It is not clear what relevance if any the sticks and the bag have to the investigation into Mr Williams' death, but DCI Sebire said that MI6 should have told her about their existence.
It was also disclosed that MI6 searched some of Mr Williams' "electronic media" without telling the police.
"What I knew was that Gareth's email accounts had been checked but I did not know that other media had been checked," DCI Sebire said.
Meanwhile, a forensic scientist has been asked to appear again at the inquest, and a new MI6 witness has been asked to give evidence anonymously.
The inquest is due to conclude on Wednesday, but there is a chance now it could continue for longer.
The painstaking investigation has drawn a 20-month blank for detectives.
On Monday, Ros Hammond, a police forensic scientist, expressed hope that tests on a green towel found in the kitchen of Mr Williams' Pimlico apartment could yield a breakthrough within a matter of weeks.
The inquest also heard from a forensic Scientist and from the pathologists who carried out three separate post-mortems on Mr Williams' body.
They told the court all their examinations had proved to be inconclusive, and spoke of the difficulties they encountered because Mr Williams' body was badly decomposed.
A period of up to 10 days passed between when they believe he died and when his body was first examined.
However Benjamin Swift, a Home Office pathologist, said that although the cause of death was "unascertained", he believed that poisoning or asphyxiation such as suffocation were "probably rather than possibly" to blame.
Tests on the Mr Williams body did not reveal signs of any poisons, but the experts said that they could not rule out the possibility that a poison could have disappeared as the body decomposed.