IT is one of the most significant scientific advances that has helped solve dozens of criminal cases. The use of DNA (deoxyribonucleic acid) profiling and testing has also led to convictions in some of the country’s high-profile “cold cases” that otherwise would have remained unsolved.
And this week it provided the most important piece of damning evidence to cage the man who abducted, raped and killed teenager Hannah Foster.
Maninder Pal Singh Kohli is starting a life sentence for the brutal murder of the studious 17-year-old who he snatched from a street just yards from her Grosvenor Road home.
But if you go back 14 years, would a jury have had the same level of conclusive proof that he was responsible?
The answer is questionable.
It was in 1995 that the Forensic Science Service (FSS) achieved a breakthrough by inventing the chemical that enables DNA profiling, following years of research that began in 1987.
As a result the organisation, which has bases across the country, pioneered the world’s first DNA database that stores the DNA of hundreds of thousands of criminals. Used by police forces in England and Wales at the early stage of any investigation, it can immediately rule in or out a potential suspect.
The FSS has the ability to carry out testing within 24 hours, faster than anywhere else in the world, while its profiling is even faster – with the results of mouth swabs or from samples of blood obtained in less than ten hours.
In Kohli’s case, detectives knew quickly after receiving his name as a suspect that he was their man.
Although his DNA didn’t flash up as registered on the database, by taking swabs from the mouths of his two young sons and his wife Shalinder Kaur, scientists were able to determine the various components belonging to the 41-year-old who was at the time on the run in his native India.
The samples matched with those on Hannah’s bruised body and gave jurors conclusive proof that he must have raped her when the results showed a one in a billion match.
Senior forensic scientist Steve Harrington, based in Chepstow, was in charge of the forensic testing of items sent to the FSS by Hampshire police.
In the early days of the inquiry, priority was given to what should be tested first – and among that was Hannah’s clothing, which revealed traces of Kohli’s blood. Spots inside Hannah’s boot were a one in 3.8 million match to him, while blood on her jacket was again a one in one billion match.
Called to give evidence in the trial at Winchester Crown Court, Mr Harrington told how his team also carried out fibre examinations – using tapings lifted from Hannah’s clothes and boots as well as other items such as the seat and headrest of Kohli’s sandwich van, in which he abducted her.
In total Hampshire police spent around £130,000 getting the material tested, including items seized by officers at the scene where Hannah’s body was found.
The costs were more than two-and-a-half times that spent in an average homicide case (normally around £50,000).
The process was so thorough that the examinations only finished after the final few of the 68 elements were submitted in December last year – nearly five years after Kohli murdered Hannah and dumped her body in Allington Lane, West End.
After six weeks of evidence during the trial, the DNA results are undoubtedly what helped jurors reach unanimous verdicts and send Kohli to prison for his crimes.