Exhibits in the Stephen Lawrence murder trial were not tampered with despite one officer deliberately sabotaging his own records, a court has heard.
Forensic scientist Rosalyn Hammond told the Old Bailey that it would have been clear if any packages had been opened without permission.
The jury has already been told that DC Paul Steed tampered with his own records after being thrown off the case when he was convicted of assault in Spain.
Ms Hammond said: "I'm not going to speculate on why or the motivations for anyone taking any actions but in the course of our examination of the packaging and the integrity of the packaging it would become apparent if there was any irregularity on the sealing in terms of records of what was sealed when and whether there was any unexplained entry into a bag, for example."
The forensic expert, who was involved in the cold case review of Mr Lawrence's murder, again dismissed defence arguments that forensic evidence got on to the suspects' clothes through contamination.
Gary Dobson, 36, and David Norris, 35, deny taking part in the gang attack in which Mr Lawrence was killed in Eltham, south-east London, in 1993.
The prosecution argues that tiny amounts of fibres, blood and hair found on clothes seized from their homes prove they were involved in the murder of the 18-year-old student.
The defence says the samples got on to the clothes through contamination during handling and storage.
In cross-examination, Timothy Roberts QC, for Dobson, said: "We suggest to you that it's not possible to dismiss completely the risk of transference of particulate and fibre material between these packages from such a source of abundant contamination."
She said she had "considered in great detail" that there was possible contamination and said that there was no risk.