The hunt to catch the Night Stalker was undermined by "basic policing errors" and "simple misunderstandings", a watchdog said today.
Confusion over a suspect and a poor response to a burglary led to the failure to arrest Delroy Grant sooner, the Independent Police Complaints Commission (IPCC) said.
Deborah Glass, IPCC commissioner for London, said: "It is clear that a simple misunderstanding had horrific consequences. Police missed the opportunity because confusion led to the wrong man's DNA being compared."
Three Scotland Yard officers - two detective constables and a detective sergeant - have faced misconduct proceedings over the botched investigation into one of Grant's 1999 burglaries.
The watchdog, which launched its probe in December 2009 after the Met expressed concerns that he should have been arrested, found a crime report from a borough burglary team included information about two different Delroy Grants which led to confusion over DNA samples.
The error contributed to a number of basic investigation inquiries not being done by either team of detectives, the IPCC added.
Ms Glass said: "This mistake set off a chain of events that was compounded by poor communications between, and within, the two teams, meaning that basic inquiries, such as arresting Grant and searching his property, were not done.
"Had an officer from either team done this then Grant may have been charged for the Bromley burglary, leading to his DNA being matched to the Minstead crimes.
"While our investigation identified poor communication and basic policing errors, in which each team believed that the other was responsible, we also have to recognise that we have required officers to account for actions taken 12 years ago, and accept that they could not have foreseen the consequences."