A judge criticised police as he jailed a stalker who murdered his ex-girlfriend five months after officers gave her a fixed penalty notice for wasting their time over him.
Mr Justice Green said police "jumped to conclusions" and "stereotyped" Shana Grice as he jailed her jilted ex-boyfriend Michael Lane for life with a minimum term of 25 years.
When she sought help from Sussex Police "she received none", he went on.
Miss Grice, 19, was found with her throat slashed in her smoke-logged bedroom at the bungalow she shared with two housemates in Brighton.
Lane, 27, waited until she was home alone before murdering her last August 25 after she decided to rekindle a relationship with her ex-boyfriend, Ashley Cooke.
It emerged during a two-week trial at Lewes Crown Court that police were told Lane pulled Miss Grice's hair and grabbed her mobile phone last March 24.
But while no further action was taken against him, Miss Grice received a fixed penalty notice for wasting police time after not disclosing she had been in a relationship with him.
Mr Justice Green said: "Shana was issued with a fixed penalty notice and a fine for wasting police time.
"In other words, she was treated as the wrongdoer and having committed a criminal offence, and Michael Lane was treated as the victim.
"There was seemingly no appreciation on the part of those investigating that a young woman in a sexual relationship with a man could at one and the same time be vulnerable and at risk of serious harm.
"The police jumped to conclusions and Shana was stereotyped."
The judge said the incident meant police treated all further complaints by Miss Grice with "scepticism".
When further stalking incidents took place, she felt her complaints would not be taken seriously by the police, he said.
Mr Justice Green added that another consequence was Lane felt the police would not act if he continued his "obsessive stalking".
Police received five reports about Lane's behaviour towards Miss Grice in the months before he killed her and then torched her room in Chrisdory Road, Brighton.
Miss Grice's mother Sharon Grice hit out at Sussex Police, saying she believed her daughter's murder could have been prevented if they had listened to her fears about him.
Sussex Police apologised to Miss Grice's family and referred themselves to the Independent Police Complaints Commission (IPCC), which has launched an inquiry.
Deputy Chief Constable Bernie O'Reilly said: "When we looked at the circumstances leading to Shana's murder, we felt we may not have done the very best we could."
Mr Justice Green said his concerns surrounded the way the complaints were handled, and he directed that his concerns be brought to the IPCC.
A two-week trial heard Lane refused to accept the break-up with Miss Grice and decided no-one else could be with her, telling a friend: "She'll pay for what she's done."
In the months before she died, Lane stalked Miss Grice, the trial heard. He put a tracker device on her car and received notifications via a phone app every time it moved.
Miss Grice also complained about her tyres repeatedly being let down, of receiving heavy breathing phone calls from withheld numbers and of Lane following her.
She was found dead, face down on her bed, in her smoke-filled room by Mr Cooke's father, Ian Cooke, after colleagues reported she had failed to arrive at work.
Mechanic Lane, of Thornhill Rise, Portslade, claimed he discovered her body then left in shock. But jurors convicted him of murder after just over two hours of deliberation on Wednesday.
In a statement following sentencing, Miss Grice's parents, Sharon Grice and Richard Green, said she would still be alive today if Sussex Police had acted on her complaints.
They said: "Shana had complained to the Sussex Police about his stalking her over five times but this was treated as being of low risk and she was given a fine for wasting police time."
Miss Grice's parents said Lane is a "dangerous and obsessive man" who had shown "arrogance and cowardice" by pleading not guilty.
They went on: "In his contemptible defence he sought to blame innocent men for his actions.
"He compounded this by relying on the wholly inadequate police assessment of risk to Shana to suggest he was no danger to her.
"We firmly believe Shana would be alive today if Sussex Police had acted to protect Shana on the many occasions she complained about Lane rather than issue her with a fine for wasting police time."