56-year-old Terence Goulding, a police designated detention officer, was on Tuesday convicted at Kingston Crown Court of the theft of between £6,000 and £10,000 cash from Kennington Police Station.
In the early hours of 18 March 2006 a bag containing a large amount of cash that had been seized from a prisoner was removed from a safe within the custody suite at Kennington Police Station in Kennington Road SE1.
Goulding was on duty as designated detention officer (a police staff role with similar status to PCSO) that night.
He was arrested on 11 December 2006 as a result of an inquiry into the theft.
Goulding will return to court for sentencing on 15 April.