Unsolved cases being reviewed after belated conviction
The man who carried out the initial forensic inquiries, following the reopening of the Phyllis Murphy investigation, said a number of unsolved murder cases were being reviewed, although he would not reveal which ones. "They would be unsolved cases where we have items of a forensic nature that could be helpful in light of DNA advances," he said.
It was the development of the advanced method of profiling a DNA sample that eventually led to Crerar being arrested and, along with other evidence, convicted. A blood sample he gave at the time provided the match. At the time, blood samples could only be used to narrow down the number of suspects, as it only went by blood group.
The advances relate to the PCR method, whereby a single flake of dandruff could be enough to link a suspect to a crime scene. PCR makes the sample grow until there is enough DNA the chemical carrier of genetic information in human beings to do analysis. Back in 1997, when DI McArdle first began to look into the Murphy case, the technology was not available in Ireland and samples taken from the crime scene to establish the profile of the murder and the blood to get a match had to be sent to England. It took two years for the process to be completed.
Scientists in the State forensic lab now have the technology to match international standards.
Dr Maureen Smyth, of the State's forensic science lab, said some 2,000 samples were studied every year. They relate to around 200 cases, all of them serious crime, such as murder, sexual assault and serious assault.
She said nobody could deny DNA evidence can be extremely strong, but added that it only forms part of any criminal case.
It places a person at the scene, but the police leg work still has to be done.
"In terms of a jury, DNA evidence is hard to ignore. But other evidence can be just as important and juries can even be switched off to science," said Dr Smyth. "People probably look at the other evidence."
But in the Crerar case, the DNA evidence was clearly the clincher, along with his alibi collapsing. According to DI McArdle, the less advanced technology of the Eighties and early to mid-Nineties would not have produced a match.
The Crerar case was a landmark case. Dr Smyth partially agrees: "It was, I suppose, because it was so old. Twenty years is a long time from the point of view of the guards and the legal team. It had to present difficulties trying to get witnesses together. But it was a case that was solved that could not have been solved without advances in DNA technology."
The technology that has become a strong arm in investigating crimes of violence was first developed in the early 1980s and perfected by Professor Alec Jeffreys, of Leicester University.
It was developed for medical reasons but its importance for forensic investigation soon became apparent. Serious crimes scenes have now taken on the appearance of mini-labs, sealed inside tents with forensic teams in lab suits and face masks to prevent pollution of the scene.
That tiny speck dandruff, hair root or piece of skin may be vital for a prosecution.
