Officers from Warwickshire Police are to call on suspects in the village of Ansley Common and the surrounding area, near Nuneaton, to collect samples. They will be compared with a DNA "fingerprint", probably obtained from a sample of the attacker's blood, discovered at the murder scene.
Naomi, 15, was found dead beneath a slide 200 yards from her home at Bretts Hall estate, Ansley Common, on 14 September after she had gone out to post a letter. Her attacker had sexually mutilated her and cut her throat. She was found by her father, Brian, and her best friend, Emma Jones.
The police will take mouth swabs from males aged 15 to 28, from which scientists can obtain a DNA profile. It is not compulsory to give a sample but police have said those who refuse will be investigated and could eventually be arrested and forced to take a test.
Mass DNA testing in a murder inquiry was first used successfully in 1987, when Colin Pitchfork, 27, a baker, was convicted with the help of genetic fingerprinting following the rape and murder of two girls.
The police believe that the technique will be useful in Naomi's murder because a psychological profile has suggested the killer is a local who knew her or was familiar with the recreation ground in which she was stabbed. Because the number of people living near by is relatively small, police have been able to compile a list of suspects from official registers.
However, a growing number of people have questioned the reliability of DNA testing. Some forensic scientists and prosecutors cite the chances of a random match as 40 million to one, but this has been challenged as grossly misleading.
Other experts say DNA profiles are only a probable, not a definitive identification of an assailant. In some communities, in-breeding can confuse the sample. Also, interpretation can differ as to how closely profiles match.
The Court of Appeal ordered the retrial of Michael Gordon, 29, who was jailed for 12 years for raping two students in Manchester. The court did not doubt the validity and value of DNA evidence in general, but said it was arguable whether the probabilities of DNA match that was put to the jury could be sustained.
In December 1992, DNA evidence against Terence Hammond, accused of armed robbery, was rejected when doubts were cast on the prosecution's claim of a probability of 10 million to one against an innocent person having the same genetic fingerprint as Hammond. The doubts centred on how the DNA comparison was made in the laboratory.
The decision to carry out the tests in Warwickshire follows a lengthy investigation in which more than 1,800 people have been interviewed and witness statements have been taken from another 441. Five men were arrested during a series of dawn raids, but no one has been charged.
The police hope to test about 150 people a week and the profile will take about 10 days to complete. DNA samples have already been taken from people at the scene on the night, including relatives, to rule them out of the inquiry.
Det Supt Tony Bayliss, who is leading the investigation, said yesterday: "It is now a question of when and not if we catch this offender. I am aware that there has been concern that the inquiry was losing its momentum. I can reassure you this is not the case.''
He added: "This testing may provoke some unusual behaviour, someone leaving the area unexpectedly. We will be watching for that."Reuse content