Essex Police failed to investigate sexual assaults because the victim was not believed due to her history of mental illness, a watchdog has said.
The Independent Police Complaints Commission (IPCC) said officers made "singular and collective failings" in the case, which stems from 2007.
A man was jailed in 2008 only after the intervention of the 56-year-old's family, the IPCC said.
Essex Police said the way it dealt with the case was "totally unacceptable."
The woman made two separate reports that her village home was broken into and that she had been seriously sexually assaulted.
After the incident in January, officers reported that no offence had occurred and the incident was disposed of.
The IPCC said the decision was made because officers did not believe the woman's account due to her mental health history.
In August, officers reported for a second time that no offence had occurred and the incident was deferred.
The woman's family and GP intervened and in September 2007, James Abrahams was arrested.
He admitted sexually assaulting the woman in August and in March 2008 was jailed for six years.
A relative of the victim made a series of formal complaints against police, the IPCC said.
Four officers fined
It served notices on 11 officers to advise them their conduct was under investigation and interviewed a number of officers under caution.
Four officers have been fined between five and 13 days' pay over the case, the IPCC added.
Another received a reprimand and one received a caution.
IPCC Commissioner Len Jackson said the serious allegations deserved a far more sympathetic, professional and determined response.
Complaints by the family that officers were "adversely influenced by the woman's mental health history" have been substantiated, he added.
"Police wrongly focused on the existence of a mental health condition, yet for instance failed to make arrangements for possible DNA evidence to be secured at the scene, despite the woman offering such evidence to the officers.
"The lack of help and support on two separate, traumatic occasions... stemmed from very poor policing and totally inadequate supervision."
Deputy Chief Constable Andy Bliss said changes had been made within the force and they had apologised to the vistim and her family.
"This case was a wake-up call to us about the way we deal with people with mental ill-health," he said.
The victim's solicitor said she was considering legal action against Essex Police.