DNA profiles from two women killed in Grangegorman nearly 20 years ago were found on a jacket belonging to murder accused Mark Nash in 2009, a jury has heard.
Mark Nash (aged 42) who has last addresses at Prussia Street and Clonliffe Road in Dublin, has pleaded not guilty at the Central Criminal Court to the murder of Sylvia Shields (aged 60) and Mary Callanan (aged 61) between March 6 and March 7, 1997.
The trial has heard that the two women were living in sheltered accommodation attached to St Brendan's Hospital in Grangegorman at the time.
Counsel for the State, Ms Una Ni Raifeartaigh SC, today called Dr Linda Williams, who told the court that she has been involved in DNA analysis and has worked in the DNA section of Forensic Science Ireland (FSI) since February 2003.
Dr Williams told the court how on September 29 in 2009 she received three self sealed plastic bags containing thread and buttons belonging to the right cuff of Mark Nash's black pin-striped velvet jacket from Dr Brid McBride, also of the FSI.
Dr Williams told the court that she realised the threads from the black velvet jacket should be kept separate from everything else and she separated the threads from these buttons for DNA extraction.
"DNA is a chemical or a complex molecule that is present in the body, its present in the skin cells and stays the same throughout your life.
With the exception of identical twins, no two people have the same DNA, Dr Williams explained to the jury of six men and five women.
Describing the procedure she took with the threads in 2009, to the court, Dr Williams explained she extracted DNA from the button threads and they were then compared to the profiles of Sylvia Shields and Mary Callanan.
Dr Williams told the court, the second step she took in the lab was "DNA quantification", to assess the "quantity and quality" of the sample.
Dr Williams then told Miss Ni Raifeartaigh that the third step she took was "DNA amplification".
The court heard how Dr Williams placed the threads into a tray and cut them open with sterile blades and then put the threads from the three buttons into a tube, but not the buttons "to maximise her chance of generating a profile."
Dr Williams told Miss Ni Raifeartaigh she got a profile match from the threads but she couldn't say from "which set of threads it came from."
"The profile taken from the threads matched Sylvia Shields' DNA profile," Dr Williams told the court.
Miss Ni Raifeartaigh asked Dr Williams if the profile generated from the threads was a "full or partial profile"?
“From the threads, it was a full profile with some minor elements” replied Dr Williams.
The court then heard from Dr Williams how a DNA profile obtained from a "particle" found inside the seam of the right sleeve of the black velvet jacket, also matched the deceased Mary Callanan.
Earlier in the day, Dr Brid McBride, who was working in the biology section of Forensic Science Ireland (FSI) for the last 25 years told Ms Ni Raifeartaigh that on September 24 2009, she examined the right sleeve of a black pin-striped velvet jacket for the microscopic presence of blood staining, belonging to the accused Mark Nash, as part of a cold case review.
Dr McBride told the court today: “I hand picked some of the remaining sewing thread, focusing on the right sleeve, I unpicked the seam and examined the lining inside the right sleeve with a low powered microscope and took samples."
Dr McBride told the court about finding "a small brown hard particle" inside the seam of the right sleeve of a black pin striped velvet jacket belonging to the accused on September 24, 2009.
Dr McBride told the court: "I observed a small brown hard particle, it was inside the seam, it would not have been exposed to air and I did a KM test for the presence of blood staining".
"I tested the actual particle and when it was tested, I got a faint KM positive reaction, with a speck inside it of 1 mm, which was indicative of blood staining," continued Dr McBride.
"It didn't look like a blood flake, it had the appearance that it was more of dried tissue."
“I removed the particle with a sterile forceps and placed it on a mini tape" she continued.
Dr McBride told the court, she did a number of other samples on the jacket but "didn't detect any other blood stains".
The same day, Dr McBride gave the "mini tape lifts" to Dr Williams for DNA profiling.
Today Dr Williams told the court she generated a profile from the "small particle, which was like a small piece of grit" and it matched Mary Callanan's profile.
The court previously heard from Mr Brendan Grehan SC, when opening the prosecution's case, how in July 2009, "a spectacular breakthrough" was made in relation to the black velvet jacket with new tests and how DNA belonging to Ms Shields and Ms Callanan, was found on it.
Earlier in the day, forensic scientist Dr Maureen Smith, now retired from FSI, was re examined by Mr Grehan about the chances of contamination on the black velvet jacket.
The court previously heard that the jacket belonging to the accused and heavily blood stained clothing and bedding found at the scene were examined in the same room at a laboratory six weeks apart.
Dr Smith told Mr Grehan it was her opinion that contamination was "not a danger in this case."
When asked by Mr Grehan about a previous contamination incident in FSI in 2013, she replied: "The contamination issue was that a DNA profile found in one case, matched another individual in another case, the items were examined in the same room on the same day, they were two unrelated cases, it was picked up and recorded in the report."
The court also heard that the prosecution have nearly finished giving their evidence.
The trial continues.