Police have failed to solve the violent murders of more than two dozen prostitutes over the past two decades, The Independent on Sunday has found. And the true number of unsolved cases is likely to be much higher, as many more women have been reported missing by friends and family, often presumed dead although their bodies have not been recovered.
Research into some of these deaths reveals widespread regional variations in the way cases are investigated. Experts claim some police forces, the media and the public become interested only when there is a hint of some sensational element – a serial killer, say – to these crimes. The deaths of individual women, they argue, often fail to capture public attention or sympathy, reflecting the negative attitudes many people still hold towards women who sell sex for a living.
Prostitutes working the streets are most vulnerable. While only one in four sex workers are on the streets, they make up three-quarters of the victims. Women who work inside in groups of three or more are the safest, according to international research.
It is only women living at the very edges of society, desperately trying to support themselves, their children, a violent pimp, and often an addiction, who are left working the streets. There are also a growing number of asylum-seekers and refugees, with no access to public funds and little, if any, social support, who work there to buy food, said Hilary Kinnell, author of Violence and Sex Work in Britain.
Campaigners argue that sex workers like those killed in Bradford will remain at risk until police forces adopt a policy of offering amnesty for all sex workers and their clients after every murder or serious attack, in a bid to encourage people to come forward.
An urgent review is needed, they say, of the legislation that forces prostitutes "underground" and into more dangerous situations. The Lib Dems have long promised to decriminalise prostitution, something their new coalition leader, David Cameron, last Friday promised to reconsider.
"Attitudes vary hugely across police regions and the action taken by police to protect, or pursue, sex workers, is often dependent on key individuals," Ms Kinnell said. "There are some areas where police still shrug their shoulders when there is violence against prostitutes, but other areas are doing much better. However, the police, the media and society, are only really interested and outraged when there is a series of murders; individual murders tend to get overlooked."
She said confused and conflicting policing methods hampered investigations. Pleas by the detective leading the investigation into the death of Rebecca Hall, 19, in Bradford in 2001 were hampered by the vice squad's failure to call an amnesty on street workers and their clients, who, as a result, were too scared to come forward with information. Hall suffered a severe beating and died from head injuries. Her body was found in an alleyway more than two weeks after she went missing. Ms Kinnell said: "Just as brutal as the killing was the anti-sex-worker policing, which carried on regardless. It was not the least bit surprising that they didn't get anywhere."
Police crackdowns on curb crawlers and street workers, especially since the 2009 Policing and Crime Act, has forced women into less well-lit and more sparsely populated areas, in order to avoid detection. Bradford sex workers and residents say women were hounded out of the established red-light area, which is a residential area, into an isolated industrial area.
As a result, women are discouraged from coming forward to report violence. One woman from Bradford, who wished to remain anonymous, has been assaulted four times in recent years. She said: "I didn't bother to report this because I knew nothing would be done."
The same happened in Ipswich in 2004 where five women were murdered by Steve Wright. Police came down heavily on sex workers, despite reports of increased attacks, driving the women into darker and more isolated areas.
Efforts to curb the demand for prostitutes also mean clients are less likely to come forward with information, or even to rule themselves out of investigations into rape or other violence, for fear of the consequences.
Cari Mitchell, from the English Collective of Prostitutes, said: "We have seen the same again and again in most towns and cities around the country; crackdowns force women into greater danger. When women, and their customers, are anxious about getting spotted by police, less time is spent assessing the safety of the situation."
One of the problems facing detectives working on these cases is that prostitutes come into contact with complete strangers every night. They often work in quiet areas without CCTV cameras, and may be isolated from friends and family.
However, forensic science advances have improved the murder conviction rate since the 1990s. This has given some of the grieving families hope.
Kent Police last month reopened the investigation into the murder of Glenda Potter, found strangled near a church in Rochester in 1991. The 32-year-old's murder was never solved, despite an appeal on Crimewatch. Officers are hoping new forensic techniques will help solve the crime, as DNA was collected at the time.
For other families, it is probably too late. Emma Caldwell was found dead a month after she went missing in Glasgow in 2005. A former stable girl, Caldwell, from Renfrewshire, became addicted to heroin in 1999 after her sister's death from cancer and took to the streets to feed her drug habit. A huge investigation by Strathclyde Police failed to secure a conviction, even though charges were bought against several men.
The Association of Chief Police Officers' lead on vice, Deputy Chief Constable Simon Byrne of Manchester Police, rejects the accusation that police are failing to take crimes against sex workers seriously. He said: "The police service is fully committed to protecting every member of the community, but, in particular, those members who are most vulnerable. This includes individuals involved in selling sex.
"The complex problems presented by the sex trade industry, which can include drugs, coercion and serious violence, as well as the many needs of the victims, mean a 'one size fits all solution' does not exist ... Acpo has recently established a working group that brings together agencies with a role to play in addressing the challenges presented by the sex trade."
Like many of the women whose killers have never been caught, those murdered in Bradford were living at the edges of society, trying slowly to climb back. A cruel combination of circumstances, relationships and difficult choices meant they ended up living lives for which many people felt little compassion.
Ms Mitchell said: "Prostitution is the visible face of economic crises. Vulnerable women will always turn to it when the chips are down. Yet our laws encourage police to persecute them rather than protect them. Cracking down on these women without dealing with the economic and social causes forces them to take more risks. We see it happening all the time. How many more times must families and communities go through this agony?"
Additional reporting by Jonathan Owen
1990 Gail Whitehouse, 23, a mother of two from Wolverhampton, was strangled and dumped in bushes in Birmingham's red-light district.
1993 Karen McGregor, 26, was not found for days after her battered and naked body was hidden in the Scottish Exhibition Centre car park, Glasgow.
1994 Dawn Shields, 19, from Sheffield, mother of a one-year-old boy, was found naked in a shallow grave at the Peak District beauty spot of Mam Tor by a National Trust warden.
2000 Vicky Glass, 21, from Middlesbrough had been missing for two months before her naked and badly decomposed body was found dumped in a stream in moorland near Danby, North Yorkshire.
1991 Maria Requena, 26, from Manchester, was found dismembered, her body parts stuffed into bags thrown into Pennington Flash, Leigh, and found by two children.
1994 Julie Finley, 23, from Liverpool, was found strangled and dumped naked in a field by a lovers' lane near Skelmersdale, Lancashire.
1991 Diane McInally, 23, was found battered to death in Pollok Park, Glasgow, so disfigured she was recognisable only by her fingerprints.
2000 ZOE LOUISE PARKER, 24, from London, had her severed upper torso dumped in the Thames near Battersea, west London, but the rest of her body has not been found.
1991 Sarah Crump, 31, found dead from stab wounds in her flat in Southall, west London. The main suspect was cleared because of insufficient evidence.
1995 Marjorie Roberts, 34, was found in the river Clyde, not far from where another prostitute's body, that of Leona McGovern, 22, was discovered earlier that year.
2002 Michelle Bettles, 22, was found strangled in woods near Dereham, Norfolk, three days after disappearing from the red-light area of Norwich.
1992 Natalie Pearman, 16, was found strangled at Ringland Hills, Norfolk. Her killer was never found but police looked at a possible link with Ipswich killer Steve Wright.
1991 Janine Downes, 22, a mother of three from Wolverhampton, was brutally murdered and her half-naked body dumped in a Shropshire lay-by.
1996 Jackie Gallagher, 26, was found dead by a roadside in Glasgow. A man was tried in 2004, but the jury did not find not enough evidence to convict him.
2001 Michaela Hague, 25, was stabbed during an attack in Sheffield. She gave police information in hospital before she died, but her killer was never arrested.
2002 Julie Dorsett, 33, from Hackney, went missing in 2002. In 2008, her upper body skeleton was found wrapped in a duvet and dumped in Walthamstow.
1992 Yvonne Fitt, 33, from Bradford was found bound and gagged in a shallow grave. She had an 11-year-old daughter. Three people were questioned but not charged.
1991 Sharon Hoare, 19, from Bristol, was found strangled in her luxury flat in Fulham, west London. Her mother had not known what her daughter did for a living.
1993 Carol Clark, 32, from Bristol was found half naked in the Sharpness Canal. She had had a heart attack after a violent blow to the throat.
1993 Mandy Duncan, 26, a mother of two who was working as a prostitute in Ipswich, went missing and was never found. An anonymous death threat was found in her flat.
1997 Tracey Wylde, 21, was found beaten to death in her Glasgow flat. She had a three-year-old daughter. In spite of the poor soundproofing, neighbours gave no evidence.
2001 Rebecca Hall, 19, died from head injuries after a sustained, vicious and brutal beating, her naked body dumped in a Bradford alley. Her case remains unsolved.
2005 Emma Caldwell, 27, from Glasgow, was reported missing after she left a hostel. Her body was found dumped in woods more than a month later.