Police made an error in reporting a call of domestic violence prior to a man throwing his girlfriend off a balcony, an investigation has found.
John McAleer was jailed for 15 years for attempting to murder his partner Danielle Hammond at a fourth-floor flat in Hemel Hempstead in June 2015.
Hertfordshire Police received four calls in relation to the couple from August 2014 prior to the fall.
One call was graded wrongly by a police staff member, an investigation found.
The force said it accepted the findings of the Independent Office for Police Conduct (IOPC) investigation.
The IOPC said the member of staff "could not recall why she made the grading, which she acknowledged was inappropriate under the circumstances".
It added the investigation highlighted "some areas of learning" for the force.
During McAleer's trial, St Albans Crown Court heard the defendant was seen pushing up his girlfriend's leg before she went over the railings.
Ms Hammond was left with injuries including a fractured skull, bleeding on the brain and major trauma to abdominal organs after falling 45ft (14m) from the flat at Lord Alexander House and landing in bushes and on a manhole cover.
Her wrists were broken, her hearing and speech was impaired and at the time of the trial she had no recollection of what happened.
McAleer had told the trial he had "stumbled into" his girlfriend before she fell.
The IOPC investigation focused on the police calls prior to the fall and found that while the staff member graded the call incorrectly, there was "insufficient evidence to show whether this grading was a deliberate action by the call handler or a mistake".
A force spokeswoman said: "Since the investigation, we have made significant changes to the way we handle domestic abuse incidents."