AS killer Peter Hastings meticulously polished his shoes, little did he know that he was zealously sealing in evidence of his horrific crime.

Hastings had realised he had the blood of his girlfriend Jean Bellis on his footwear after stabbing her to death in his Birmingham home in 1993. What he didn't realise was that, by polishing his shoes, he was wiping on a protective sheen, sealing in the microscopic specks of blood which would later incriminate him.

Shortly after his girlfriend's death, Hastings was charged by police with her murder, only for the case to be dropped on the grounds of insufficient evidence. It was six years later that advances in forensic science led to his conviction. A DNA profile could be picked out from the blood and he was found guilty of murder and received a life sentence in prison.

The Hastings case is one of hundreds where the rapid advances in DNA profiling are helping to turn over criminals who thought they had got away with their crimes long ago. Today, a DNA sample - the chemical which carries genetic information from one generation to the next - can be taken from samples naked to the human eye. A few skin cells left on a dead body; a drop of saliva or even badly degraded blood stains are all that is needed to create a DNA profile capable of matching a suspect. And where it may once have taken three weeks to receive the results, now the police can get their DNA profiles in three to four days.

"It has leapt ahead at a phenomenal rate, and that is very exciting," says Geoff Knupfer, a former Detective Chief Superintendent and deputy director of the Centre for Applied Socio-Legal Studies at Teesside University.

"In the early days, in the mid-1980s, it was sophisticated but it wasn't as discriminatory as it is now. It is enabling the police now to go back to a number of major crimes and look at the exhibits. They can look at saliva left on a cigarette or chewing gum, all kinds of areas that we couldn't previously have got DNA from."

With a national DNA database now in existence, the chances of catching a killer or rapist, even in long ago cases, is stronger than ever. It is with this in mind that Northumbria Police yesterday launched Operation Phoenix, one of the first of its kind in the country.

The force has already earmarked 300 unsolved rapes between 1992 and 1997 where they could get positive results by re-visiting exhibits from past crimes. They are expecting to look at hundreds more, spanning the last two decades, and the chances of a successful outcome are high.

The database, perhaps one of the most powerful crime-fighting weapons to date, was set up by the Forensic Science Service (FSS), an executive agency of the Home Office, and already contains more than one million DNA profiles. For every person who faces court proceedings, a swab is taken from their mouth for a DNA sample which is incorporated into the database. Remarkably, it is scoring hits of between 1,500 to 1,700 crimes per week, matching suspects with crime scenes and crimes with other crimes to establish links.

It was the database which caught the killer of 14-year-old Roy Tutill, who was sexual assaulted and murdered in April 1968. As developments were made in forensic science, semen stains were taken and kept in the freezer, for a time when they could be put on the database.

It was 33 years later that police got their man in the form of Brian Lunn Field from Solihull in the West Midlands. Field had been stopped by police in 1999 on a drink-driving offence and a routine DNA swab was taken and fed into the database. Further re-testing proved a match and Field eventually changed his plea to guilty and was sentenced to life imprisonment.

Cathy Turner is a major crime specialist advisor based at the FSS's Wetherby laboratory in West Yorkshire, which takes samples from police forces across the North-East.

"Right at the very start of DNA profiling it was the case that you would need quite a large amount of material to generate a profile and the test was reserved for the more serious cases - it was an expensive technique at the time. As time has gone on, the tests have become much more sensitive and more robust and you can deal with degraded and old samples much more effectively," she says.

It is the painstaking efforts of the 2,500 people working for the FSS which also ensures killers such as mechanic Roy Whiting are locked up for life. It took forensic workers more than 17 months to meticulously gather enough DNA evidence for Whiting, 42, to end up in court, for the killing of Sarah Payne.

Sarah had gone missing in July 2000 after playing in a field near her grandparents' home in West Sussex. Scientists at the FSS were able to match fibres found on the Velcro strap of the eight-year-old's shoe to both a red sweatshirt and a clown curtain found in Whiting's van.

There were also fibres from the red sweatshirt, socks and the driver's and passenger seats of the van found in Sarah's hair. A blonde hair found on Whiting's shirt also turned out to be hers. The evidence helped convict Whiting of kidnap and murder.

DNA evidence has increasingly been taken more seriously in the courts over the years.

Says Mrs Turner: "I think the courts have certainly accepted DNA evidence much better, but the technology is well validated and it's backed up with statistical evidence.

"If you have a profile which matches, it tends to be accepted and the courts will maybe look at other areas to see how that DNA was deposited. If you have a full profile, and that is a one in a billion chance, then they would look at the area in which the crime was committed, for example. But I would say there are very few cases where people will go to court without additional evidence."

Like many involved in forensic science, Mrs Turner is understandably reluctant to discuss future advances in technology. You never know who may be reading this article, after all. "We're a bit restricted in what we can say," she says.

But she points out that they can already tell the gender of a person from DNA and there are developments in respect of hair colour and other distinguishing features. There have also been reports that in a few years' time police officers will even know the skin shade and facial features of the type of person they are looking for.

As a former police officer, Geoff Knupfer is aware the police will have to adapt to the technological advances themselves, if they want to secure convictions.

"It is essential, more than ever before, that the last thing you should do if you've been to the crime scene is go and talk to the suspect," he says. "If there were certain fibres at the crime scene which were later found to belong to the suspect and the officer went from the crime scene to arrest him, it could be argued that he had contaminated him. These are the kind of difficulties you face as the technology gets more sophisticated.

"But I think DNA profiling is a very positive way of either implicating someone or eliminating them. The days of police interviewing people, hoping that they may confess, are long gone."