The death of MI6 spy Gareth Williams, whose body was found in a padlocked sports bag, was probably an accident, UK police have said.
Last year, a coroner said it was likely Mr Williams, 31, from Anglesey, had been unlawfully killed.
But Deputy Assistant Commissioner Martin Hewitt said a review of evidence had found "it was more probable" no other person was present when he died.
The code-breaker's body was found naked at his London flat in August 2010.
At the time of his death, Mr Williams - originally from Holyhead in north Wales - had been on a three-year secondment with MI6 from his job as a communications officer at the GCHQ "listening post" in Cheltenham, Gloucestershire.
Police officers had gone to his flat in Pimlico after colleagues raised concerns for his welfare.
His body was discovered inside a zipped-up red North Face sports holdall, in the empty bath of his bathroom.
It had taken a week for MI6 to investigate Mr Williams' disappearance, meaning a post-mortem was carried out nine days after he died - when there had already been extensive decomposition of his body.
The examination by a Home Office pathologist failed to determine the cause of death.Deep-clean 'fallacy'
During a seven-day inquest in May 2012, the question of whether Mr Williams could have padlocked himself into a bag in a bath was central.
Coroner Fiona Wilcox concluded that "most of the fundamental questions in relation to how Gareth died remain unanswered".
But she said he was, "on the balance of probabilities", unlawfully killed.
At a briefing on Wednesday, DAC Hewitt said he was satisfied that it was "theoretically possible" Mr Williams could have padlocked the bag from the inside.
But he said there was no evidence that the MI6 officer had intended to take his own life or that his death was connected to his work.
There were about 10 to 15 traces of DNA in the flat from which it had not been possible to gain full DNA profiles, but all other DNA profiles and fingerprints had been eliminated, said DAC Hewitt.
He also said there was no evidence that Mr Williams' flat had been forensically cleaned, adding it was a "fallacy" that it had been deep-cleaned in such a way that only certain DNA was left in the premises.
Mr Williams' family are understood to be standing by the coroner's findings.