The Metropolitan Police's Deputy Assistant Commissioner Martin Hewitt said they are trying to "trace unidentified DNA" to understand what happened to Gareth Williams.
He added that the case "remains a current investigation".
Whatever the coroner's verdict today at the inquest into the death of MI6 spy Gareth Williams, many questions will remain unanswered.
Last day of the inquest into the death of Gareth Williams
Experts can't rule out the possibility that the MI6 spy found dead in a bag, locked himself in unaided, before dying.