DNA found in a getaway car used in the shooting of two British soldiers is almost six trillion times more likely to belong to one of the alleged murderers than someone else, a court heard.
A match between another genetic sample discovered in the vehicle and the second man accused of the killings of Mark Quinsey and Patrick Azimkar is around six billion times more probable than it matching another person, a DNA expert told Antrim Crown Court.
Sappers Quinsey, 23, and Azimkar, 21, were shot dead by the Real IRA as they collected pizzas with comrades outside Massereene Army base in Antrim town in March 2009.
High-profile republican Colin Duffy, 43, from Forest Glade in Lurgan, Co Armagh, and Brian Shivers, 46, from Sperrin Mews in Magherafelt, Co Derry, deny two charges of murder and the attempted murder of six others – three soldiers, two pizza delivery drivers and a security guard.
On the sixth day of their trial, American DNA specialist Dr Mark Perlin revealed the results of tests he carried out on data from a seat belt buckle and a mobile phone found inside the Vauxhall Cavalier getaway car, which was abandoned partially burnt out on a country road just a few miles from the shootings.
Dr Perlin is renowned in the scientific world for developing a computer based statistical system – True Allele – which analyses forensic samples containing the DNA or two or more people.
The expert compared the results of swabs taken from the buckle and the phone along with samples of Duffy and Shivers’s DNA.
As the two defendants watched from the dock, Dr Perlin told judge Mr Justice Anthony Hart that a DNA sample found on the belt buckle was 5.91 trillion times more likely to be Duffy’s than someone else’s.
“A match between the buckle and Mr Duffy would be 5.9 trillion times more probable than a coincidental match,” he said.
He said a sample retrieved from inside the mobile phone was 6.01 billion times more likely to belong to Shivers than another person.
Dr Perlin, whose technique was used in a bid to identify the victims of 9/11, also carried out tests on a matchstick found at the car that the Crown claim also links Shivers to the scene.
The expert is due to reveal his findings on the match to the court tomorrow but Shivers’ defence lawyer Patrick O’Connor today voiced concern over the evidence.
The QC said Dr Perlin had earlier this month revised his original calculations in regard to the matchstick after receiving amended data, but that the defence had only received the new results today.
Mr O’Connor did not make an official application in regard to the evidence but indicated a concern about a “fair trial” because his team had no time to analyse the revised figures.
“We are in absolutely no position to deal with this drastic revision at all,” he said.
Earlier both Mr O’Connor and Barry McDonald QC, representing Duffy, questioned the reliability of Dr Perlin’s True Allele statistical approach.
They both indicated they would be challenging whether the judge in the non-jury trial should admit it as evidence
Mr McDonald said: “The reliability of that method is to be challenged.”
Mr O’Connor said the evidence was not strong enough for the judge to take it into account when reaching his verdict.
“The methods of Dr Perlin in reaching his conclusions fall below the threshold of reliability to be admissible in court,” he explained.
Mr Justice Hart said the evidence should be heard and challenged by the defence before any ruling on its admissibility was made.
Dr Perlin’s “cybergenetic” technology has emerged in the last two decades as an alternative to the long established human review technique to extract individual profiles from mixed DNA.
Before using his method for forensic use, True Allele had originally been developed as a diagnostic test to identify muscular dystrophy.
He told the court that it is now recognised by a range of international standards organisations and was recently approved for use in the New York police’s forensic labs.
The expert said True Allele data had also been admitted as evidence in criminal cases in the USA.
But he added that in one case in England a judge had decided not to allow True Allele evidence to be heard before the jury.
Dr Perlin said the system was used in the aftermath of the World Trade Centre attacks to help identify victims’ charred remains.
He explained he worked with data from 18,000 human body pieces recovered from the site in a bid to match them to profiles of 2,700 missing people.
He said his system had been subjected to rigorous validation tests by the US’s National Institute of Standards and Technology.
The expert said human review techniques did not use all the genetic data in a sample
“The effect of discarding the data is typically to lose information,” he said.
Judge Hart asked did that mean his approach provided a “better informed picture of any match probability”?
“Exactly My Lord,” the academic replied.
He said the computer was also totally objective because it only ran a statistical test and was not setting out to find a match with a suspect’s profile.
Dr Perlin added: “The computer’s goal is not to produce a big number or a small number, it’s to produce the most accurate number.”
Crown counsel Terence Mooney QC asked Dr Perlin to explain to the court why his system was more informative than other techniques.
“Simply because it makes more use of the data that’s present,” he responded.
Mr Mooney noted that a defence expert had challenged Dr Perlin’s technique in a written report in which he claimed more validation of its reliability had to be undertaken.
Dr Perlin said around 15 studies to establish the validation of True Allele had been completed or were ongoing.
The trial continues.