A forensic scientist told a murder trial jury today that a button from a jacket worn by a man accused of murdering two women eighteen years ago produced a negative DNA result when examined in 1998.
Mark Nash (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 (60) and Mary Callanan (61) between March 6 and March 7, 1997.
The court has heard evidence that the black pin-striped velvet jacket was worn by the accused Mark Nash on the night of Thursday March 6, 1997 when he was attending a charity quiz at the GPO on O'Connell Street.
The black pin-striped velvet jacket is of relevance as 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.
Today Former Det Inspec Brendan McArdle of the Ballistics Section of the Garda Technical Bureau, now retired, told the court how he handed over exhibits related to the murders of Sylvia Shields and Mary Callanan to a forensic scientist by the name of Mr Matthew Greenhalgh who worked in Cellmark Diagnostics, a DNA testing service based in Oxfordshire in the UK on September 18 1998.
Examined by Ms Una Ni Raifeartaigh SC acting for the State, Mr Greenhalgh told the court he was a forensic lab manager at the time and has been a forensic scientist since 1979, specialising in the area of DNA profiling.
Mr Greenhalgh explained to the jury of six men and five women how DNA is a "complex chemical present in many cells of our body and it is possible to extract that from blood stains and compare stains with the DNA of another person to see if they are the same or different.”
Reading from the exhibits transfer form, Mr Greenhalgh told the court he received a DNA profiling request for three buttons and three threads which were received in separate plastic bags and three blood samples from the accused Mark Nash, Sylvia Shields and Mary Callanan.
The court heard that he was told to concentrate on the first button and if he didn't get a result from that, he was asked not to continue to examine the other items.
Mr Greenhalgh told the court that the DNA technique used was called "Short tandem repeat" (STR) and it has been superseded since 2000.
Mr Greenhalgh told the court, how the first button was swabbed by his colleague who tried to extract DNA from it but because it produced a negative result, a DNA profile wasn't achieved.
“There was nothing to compare it with so we didn’t go on to consider any of the other buttons and threads” said Mr Greenhalgh.
The items then remained in storage in the lab until they were collected.
As the items produced to the court today, seemed not to be contained in the individual sealed bags, Mr Greenhalgh was asked under cross examination by Mr Hugh Hartnett SC for the accused if something had gone wrong with the items?
"It would appear the bulk of the items have been removed from their empty bags, I presume that was the lab here" replied Mr Greenhalgh.
"It would be normal to return the item in the bag it came, I'm not sure why the button is not in the bag" added Mr Greenhalgh.
Mr Hartnett put it to Mr Greenhalgh if there was a cause for having separate sealed bags?
"If the button has already been analysed and found to be negative, we send them back as sealed” replied Mr Greenhalgh.
The court also heard from Miss Rosie Amrit, a DNA lab manager at the time who has been employed at Cellmark since 1998 and dealt with certain items which included three buttons and three items of fabric in relation to the Grangegorman murders in January 1999.
The last witness of the day was now retired Det Sgt Alan Bailey who is currently writing a book on the Grangegorman murders which he started when he was serving in An Garda Siochana and previously had a draft of his script which is a work in progress, given to the court.
Cross examined by Mr Hartnett regarding Martin Stafford, a criminal and suspect for the 1997 double murder of the two women who lived in Grangegorman, Mr Bailey told the court, Stafford was eliminated from the investigation on the "basis of the forensics examination on the car."
The court previously heard that Stafford "was a person of particular interest" as he had hijacked a car on March 6 1997 and assaulted a prostitute on the same day.
"A forensic inquiry managed to put Stafford totally out of the picture?" asked Mr Hartnett.
Mr Bailey told the court, a team was sent down from the Garda Technical Bureau to examine Stafford's car by taking samples.
Mr Hartnett said: "Can I suggest there was no report, and the only activity was taking five sellotape lifts off some portion of the car?"
Mr Bailey disagreed and said there was an awful lot of structural work done on the car and it was "quite extensive".
The trial continues.