DNA profiles from two women killed in Grangegorman nearly 20 years ago were found on a jacket belonging to Mark Nash in 2009, a jury has heard.
Mark Nash (42) has pleaded not guilty at the Central Criminal Court to the murder of Sylvia Shields (60) and Mary Callanan (61) between March 6th and March 7th, 1997.
The trial has heard that the two women were living in sheltered accommodation attached to St Brendan's Hospital in Grangegorman, Dublin at the time.
Counsel for the State Úna Ní Raifeartaigh SC, today called Dr Linda Williams, who told the court that she works in the DNA section of Forensic Science Ireland (FSI).
Dr Williams told the court how, on September 29th, 2009 she received three self-sealed plastic bags containing thread and buttons belonging to the right cuff of Mark Nash’s black pinstriped velvet jacket from Dr Brid McBride, also of the FSI.
Dr Williams told the court that 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.
Dr Williams explained that she extracted DNA from the button threads and compared them to the profiles of Sylvia Shields and Mary Callanan.
She then conducted “DNA quantification”, to assess the “quantity and quality” of the sample. The third step she took was “DNA amplification”.
Dr Williams said that she got a profile match from the threads but she couldn’t say from “which set of threads it came from”.
She said: “The profile taken from the threads matched Sylvia Shields’s DNA profile.
“From the threads, it was a full profile with some minor elements.”
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.
Cold case review
Earlier in the day, Dr McBride told the court that on September 24th, 2009, she examined the right sleeve of a black pinstriped 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: “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 said: “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.
“I removed the particle with a sterile forceps and placed it on a mini tape.”
Dr McBride said she gave the “mini tape lifts” to Dr Williams for DNA profiling on the same day.
Earlier in the day, forensic scientist Dr Maureen Smith, now retired from FSI, was re-examined by prosecution lawyer Brendan Grehan SC about the chances of contamination on the black velvet jacket.
The court previously heard that the jacket and heavily bloodstained 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”.
The trial continues.