Exhibits in the Stephen Lawrence murder trial were not tampered with despite one officer deliberately sabotaging his own records, a court heard today.
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.
Today 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, asked: "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.
Today the jury was shown photographs of the seals of exhibit packages where the Sellotape appeared to have trapped or picked up fibres and debris.
These included a jacket and cardigan seized from Dobson's house and Mr Lawrence's cardigan, jacket, body warmer and T-shirt.
Mr Roberts also outlined a number of facts that he argued heightened the risk of contamination in this case.
These were that Mr Lawrence's clothes were heavily bloodstained and that they were cut off by medical staff, creating a "shower of fibres" over all the exhibits.
Exhibits were moved several times during the 14 years between Mr Lawrence's death and when the exhibits were taken to the LGC lab.
In addition suspect and victim packages were overbagged together and adhesive seals failed with time, he said.
Stephen Batten QC, for Norris, said that there would need to be "a lot of coincidences" if hairs found on jeans seized from Norris's house had not got there by contamination.
But Ms Hammond replied: "I disagree that it's coincidence."
The forensic expert reviewed the possibility of contamination throughout the investigation, including work done by her own colleagues at a company called LGC.
Prosecutor Mark Ellison QC asked her how she would respond if there were an "unuttered suggestion you bent your proper position as a scientist to favour your colleagues" in her evaluation.
She replied: "That's absolutely not true and an insult to my integrity."
He also asked whether she attached any weight to the fact that such a small amount of forensic evidence was found on the Dobson and Norris clothing.
Ms Hammond said: "Quite a large number of items were examined and were subjected to very detailed and thorough examinations and yet evidence was only found on a few of them. Despite different histories of each of these items, if contamination was a possible explanation then there may be other items where it might be more likely to have taken place."
The trial was adjourned until Monday.