Wayne Couzens was accused of flashing six years ago but Kent Police failed to investigate, it can be revealed.
Couzens, a serving Met Police officer, kidnapped Sarah Everard in Clapham on March 3 before raping and killing her.
Now it seems that chances to stop him were missed as two police forces stand accused of failing to investigate allegations of flashing.
The Independent Office for Police Conduct (IOPC) said on Friday that Kent Police failed to investigate an incident of indecent exposure when Couzens was working as an officer for the Civil Nuclear constabulary (CNC).
A separate probe is underway to investigate whether two Met police officers breached professional standards after they failed to investigate allegations of flashing just days before Ms Everard was killed.
IOPC said that 12 officers had been served with gross misconduct or misconduct notices in relation to Ms Everard’s case.
Three officers have been served with gross misconduct notices after a probationary Met Police constable allegedly shared an inappropriate graphic relating to the case with officers over social media.
IOPC said “a number of forces” also breached standards of professional behaviour by sharing information linked to the prosecution of Couzens via a messaging app.
An investigation into how Wayne Couzens sustained head injuries while in custody on both March 10 and March 12 following his arrest has almost concluded, the IOPC said, with all officers involved treated as witnesses.
The IOPC said the serving of misconduct notices does not necessarily mean that disciplinary proceedings will follow.
Couzen admitted the kidnap and rape at a hearing last month, and on Friday appeared at the Old Bailey via video link to plead guilty to murder.
Sitting with his hands clasped between his knees and head bowed throughout the hearing, Couzens said “guilty ma’am” as he entered the plea.