A partial DNA profile generated from material preserved 42 years ago matched that found on a beanie hat taken from a murder accused, the Central Criminal Court has heard.
UK forensic scientist Dr Jonathan Paul Whitaker testified that the probability of the recovered DNA profile originating from someone unrelated "to the man in the beanie hat" would be one in 23,000.
Dr Dorothy Ramsbottom, who also gave evidence on Monday, said that based on a database of the Irish population, it was at least 20,000 times more likely that the recovered DNA was a match to that found on the beanie hat rather than an unrelated person.
Evidence has been given that a microscopic slide containing material from a vaginal swab of the victim had to be sent to the UK in 2008 to generate a DNA profile, as Ireland lacked the techniques to interpret low amounts of DNA at the time.
The jury has heard that the pathologist who carried out the post-mortem examination on Nora Sheehan found bruising in the anterior wall of her vagina, and it showed the presence of spermatozoa.
Dr Robert Dermot Coakley conducted the post-mortem examination on Mrs Sheehan on June 13th, 1981, but died weeks after carrying out the examination in August 1981.
Noel Long (74), with an address at Maulbawn, Passage West, Co Cork, has pleaded not guilty to murdering 54-year-old Mrs Sheehan between June 6th and June 12th, 1981, at an unknown place within the State.
Her body was found by forestry workers at The Viewing Point, Shippool Woods in Cork six days after she went missing.
Technological advancements
Dr Whitaker from Forensic Science Services (FSS) in the UK continued giving his direct evidence in the trial on Monday.
He told Brendan Grehan SC, prosecuting, that Low Copy Number (LCN) was a more sensitive DNA profiling technique capable of detecting DNA in much smaller amounts and where a sample is old or has had the opportunity to degrade.
The witness said the LCN method stopped being used in 2012 as there had been another development in DNA profile testing within the scientific community.
"There is no real requirement to have it today as a result of advancements in technology," he added.
In November 2008, Dr Whitaker received a microscope slide of cellular material taken from the body of Mrs Sheehan and a blood stain card from the victim.
Dr Whitaker tested the microscope slide using the LCN methodology, what he said was the most appropriate method available, to maximise the chance of getting a DNA profile from the sample as it was quite old and taken from the decomposed body of the victim.
The blood stain card of Mrs Sheehan was processed by the standard DNA method.
Dr Whitaker agreed that on May 5th, 2022, he received the result of a DNA profiling test performed on a black beanie hat obtained from an address as Maulbawn, Passage West, Co Cork.
Dr Kristen O'Connor, from Forensic Science Ireland, has testified that she received five items belonging to Mr Long on December 1st, 2021, for DNA testing and one of these was a black beanie hat.
Dr Whitaker told the jury it was possible to observe sperm cells on the microscopic slide.
Asked by Mr Grehan what concentration of sperm cells were on the slide, Dr Whitaker said there were approximately 5,000, but that sperm cells have no bearing on the profile interpretation.
The witness said the next step was to separate epithelial and semen cells.
Dr Whitaker said when he tested the epithelial part of the vaginal swab he obtained a female DNA profile which matched the DNA profile obtained from Mrs Sheehan's blood stain card.
Dr Whitaker said a male partial profile or incomplete profile was developed from the seminal part of the sample in the microscope slide. His opinion as to why the seminal fraction was an incomplete profile was because of the poor quality of the DNA.
"It's broken down because of its age or [because] that bacteria has affected the integrity of the DNA; we are dealing with a profile obtained some 28 years earlier," he said.
DNA profile
The witness said a DNA profile from the beanie hat provided to him in May 2022 was compared to the profile obtained from the seminal part of the microscope vaginal slide.
Dr Whitaker said the profile taken from the semen on the microscope slide matched the DNA recovered from the beanie hat.
The witness said if the male DNA profile on the microscope slide had not come from the person whose DNA profile was on the beanie hat then it must have come from somebody else who by chance had the same DNA profile.
Regarding the probability of that particular DNA profile originating from someone unrelated "to the man in the beanie hat", he said it would be one in 23,000.
The next witness, forensic scientist Dr Dorothy Ramsbottom said she was asked to offer her view of a match between material on Mrs Sheehan's vaginal swab and the black beanie hat based on the Irish population.
She estimated it was at least 20,000 times more likely that the DNA matched that on the beanie hat rather than an unrelated person based on the database of the Irish population.
Under cross-examination, Michael Delaney SC, defending, asked the witness what the likelihood ratio would be if a full profile obtained from the semen on the vaginal swab had matched the profile obtained from the beanie hat.
Dr Ramsbottom said it would be a thousand million times more likely where there was a match between two full profiles.
Under cross-examination by Mr Delaney, Detective Garda David Barrett, of Bandon Garda station, agreed that this case had been with the Serious Crime Review Team from 2008 to 2016 before it was returned to Bandon Garda station.
Det Gda Barrett also agreed that he had undertaken an extensive search in Bandon District Headquarters, which comprised of seven Garda stations, for exhibits in the case.
He further agreed that 281 items were recorded on the exhibit log from the investigation but that no items were recovered as part of his search. These items included a blue and white flowered dress found on Mrs Sheehan's body, as well as a blue coat, a shoe with a gold buckle and tights found at the scene.
The remains of a vaginal swab taken from the deceased's body was not recovered either.
The witness said the accused had been charged with the offence on June 28th, 2022.
At the close of Monday's proceedings, Mr Grehan told the jury that the prosecution had completed its evidence in the trial. Mr Delaney said an issue of law arises in the absence of the jury which would take two days.
The trial continues on Thursday before the jury of seven men and four women.
