A bag strap left at the scene of Stephen Lawrence's murder was originally believed to have been discovered further away after punctuation in police notes was misread, it has emerged.
It had been thought the item was found around 80 to 90 metres (260 feet to 295 feet) away from the spot where the 18-year-old was attacked in Eltham, south east London, on April 22 1993.
However, officers established in 2014 that the strap was actually discarded only a few metres from where Stephen was set upon.
Chris Le Pere, the senior investigator in the case, described the discrepancy as an "honest mistake", adding: "In my judgment there is no misconduct involved in this."
He said: "We've established since I took over the investigation in February 2014 that it is not where the original investigation thought it was."
Mr Lawrence's bag was found around 6 metres (20 feet) from a footway, his blood was 10 metres (32 feet) away and the strap was 15 metres (50 feet) away, according to the revised position.
The location of the strap was correctly recorded in notes by examiners who recovered exhibits at the scene.
However, the examiners' statements were written up for them as they were unavailable and they did not have their notes to hand when the statements were signed.
Asked about the difference in the location recorded in the notes to the statement, Mr Le Pere said: "Because the way the actual examiners' notes are ... the punctuation hasn't been read correctly."
He added: "It is a misinterpretation of the scene examiners' notes." Mr Le Pere said he did not know who wrote the statements up.
Mr Lawrence was stabbed to death by a group of up to six white men in an unprovoked racist assault as he waited at a bus stop with a friend.
In January 2012, Gary Dobson and David Norris were found guilty of being involved in the attack and jailed for life.
Scotland Yard renewed its public appeal for information after improvements in forensic testing produced a DNA profile of an unidentified female from the black leather bag strap.
Detectives believe the profile belongs to the main user of the bag and are attempting to trace her.
Mr Le Pere stressed the female is not a suspect.
He said: "She is a witness. There is no evidence to suggest a female was involved in the murder of Stephen Lawrence."
The female may have been a victim of a theft or the bag or strap may have been given to someone unwittingly, Mr Le Pere said.
He said he believed the strap was left at the scene by the suspects, with one possible theory being explored that it was an "adapted offensive weapon".
Officers have spoken to around 110 people in connection with the line of inquiry. Fifty of these individuals gave DNA samples, 46 refused, 12 failed to respond to police requests and the remainder were eliminated for medical reasons.
A reconstruction and appeal was shown on BBC's Crimewatch on Monday night.
Mr Lawrence's father Neville pleaded with anyone with information to come forward, saying: "One small little bit of information can bring it all together."
:: Anyone with information is asked to call the Met Police on 101 or Crimestoppers anonymously on 0800 555 111.