By Chris Summers
Three prostitutes have been found dead in Suffolk and there are now concerns about two other women who have gone missing. How do police handle such killings?
Vicky Glass was among dozens of street girls murdered in Britain in recent times
Carol Clark's family are still waiting for her murder to be solved, 13 years on.
The 32-year-old Bristol prostitute left her boyfriend on 27 March 1993 to work in the centre of the city. The following day her body was found in the Sharpness Canal in Gloucestershire.
Carol is one of dozens of street girls who have been murdered in Britain in the past 20 years and only a small minority of these killings have been solved.
Gail Whitehouse, Lynne Trenholme, Natalie Pearman, Julie Finlay, Vicky Glass, Tracy Wylde. The list goes on and on.
They often had the same sad biographies, marked by drug addiction which led them to sell their bodies to fund their habit.
The problem facing detectives working on these cases is that a prostitute comes into contact with complete strangers every night.
If they are killed by a "punter" the police will be looking for a needle in a haystack.
Sir Michael Bichard made recommendations about inquiries
Suffolk Police will be throwing huge resources at this investigation this week in the hope of turning up a key piece of evidence which could give them a lead before the inquiry loses momentum.
They will be looking for CCTV footage showing one of the girls getting into a car, or perhaps an eyewitness who noticed some sort of commotion. They will also be waiting for forensic tests to be carried out which might give them a clue.
The Bichard Report, which came out in the wake of the Soham killings, made a number of recommendations about how murders should be investigated and information shared between forces.
Four of these recommendations were implemented by the National Centre for Policing Excellence (NCPE), which is based at Wyboston in Bedfordshire.
The NCPE developed a set of guidelines, based on "core investigative doctrine" which all detectives are now trained in.
This includes basics such as cordoning off a crime scene, preserving the evidence, taking witness statements and making house-to-house inquiries.
But it also includes a wider philosophy. Detectives are now trained to follow the evidence and hope it will lead to a suspect, rather than settle on a suspect and try to make the evidence fit.
This is designed not only to prevent miscarriages of justice, but to ensure that detectives remain open-minded and inquiries do not end up following dead ends.
Another recent development in investigating major crimes is Opsline, a 24-hour resource which is available for all British police forces.
NCPE Spokesperson, Erica West explained: "The Senior Investigating Officer (SIO) can contact the Opsline facility, explaining the situation and request further professional operational assistance if needed. We have a list of experts in various fields who can work closely with the SIO on the case and provide additional operational support, including geographical profilers or forensic psychologists".
She said the NCPE had appointed a Regional Operations Manager - who is at inspector level - to work closely with the SIO, Detective Chief Superintendent Stewart Gull.
But Ms West pointed out: "We do not parachute people in to take over. We are only there if they need us and we will offer as much support as they want."
One thing which marks out the Suffolk cases from previous clusters of prostitute killings is the very short window of time they occurred within.
It is very unusual for serial killers - in real life, rather than the movies - to strike so often in such a short space of time.
The Yorkshire Ripper, Peter Sutcliffe, who is often seen as the classic example, killed 13 women over a five year period. The shortest gap between killings was 10 days.
Lorry driver Alun Kyte was jailed in March 2002 for killing two prostitutes
But Gemma Adams and Tania Nicol went missing from the same red light district within days of each other, and it appears that at least one other prostitute from the same area may also have met her death in this same period.
All of which suggests the killer may be local and may have connections with each of the dead girls.
Neither girl was sexually assaulted which also suggests the motivation may lie elsewhere.
From time to time, there are killers at large who target prostitutes.
In March 2000 Alun Kyte, a lorry driver from Stafford, was jailed for life for murdering two Midlands prostitutes, Samo Paull and Tracey Turner. Detectives have since interviewed him in jail in connection with several other prostitute murders.
In 1996 a national database was set up, under the name Operation Enigma, in an attempt to look for possible links between such unsolved murders.
It is to be hoped that the Suffolk murders are solved quickly an do not end up being added to the growing list of unsolved killings.