Graham Dwyer trial: Semen matching that of accused found on O’Hara’s mattress

Beanbag cover ‘stab or cut’ and blood matching that of Elaine O’Hara

A forensic scientist has told the murder trial of Graham Dwyer that semen matching that of the accused was found on three parts of Elaine O'Hara's mattress.

Mr Dwyer (42), an architect from Kerrymount Close in Foxrock, is charged with murdering childcare worker Ms O’Hara (36) on August 22nd, 2012. He has pleaded not guilty.

Dr David Casey with the Forensic Science Laboratory at Garda Headquarters said he carried out DNA testing of several items recovered by gardaí from the area of Killakee Mountain where Ms O'Hara's skeletal remains were located, a second area nearby, the Roundwood reservoir, Ms O'Hara's apartment at Belermine Plaza, Stepaside, and the home of Mr Dwyer in Foxrock.

Dr Casey told the jury he carried out tests on items to examine them for semen and blood for purposes of DNA profiling. The samples, he explained to the jury, can then be compared to DNA reference samples in order to ascertain an identity.


In terms of the mattress from Ms O’Hara’s apartment, he said semen was found in five areas on the mattress.

Of these five areas, three of them had full DNA profiles matching Mr Dwyer, while the other two areas has a partial match to Mr Dwyer. A non-semen stain on the mattress also had a partial match to Mr Dwyer.

Also examined were bloodstains on the mattress. Dr Casey said he carried out DNA profiling on four areas of the mattress where there was blood. Two of the areas had puncture marks, and a DNA profile obtained from those holes matched that of Elaine O’Hara.

There were five “stabs or cuts and three holes” mainly at the top of the mattress.

Also examined was a rug, which had no blood or semen on it and was undamaged beyond normal wear and tear.

A beanbag cover was bloodstained and Dr Casey sampled five areas of it. A DNA profile obtained from each of those five areas matched that of Ms O’Hara.

There was also “a stab or cut” to the beanbag cover.

Dr Casey said he also examined a black dress, possible made of PVC material, which had no semen on it but some other staining inside the hem. There was insufficient DNA to obtain a profile from the dress however.

Under cross-examination from defence barrister Ronan Kennedy, Dr Casey said he examined knots on the dress, which would sometimes yield positive results in terms of ascertaining a full DNA profile.

The absence of such a result in this case however “certainly doesn’t mean the dress wasn’t worn”, he said.

In terms of a gas mask that was recovered from Ms O’Hara’s apartment, there was also insufficient DNA inside it to obtain a profile.

The same was true of a rope that was seized from the apartment by detectives.

Dr Casey also gave evidence of his examination of a pair of tracksuit bottoms recovered from the area where Ms O’Hara’s remains were discovered.

They were in “poor condition” with several holes in them. There was also some “vegetation staining”. The inside, he said, was also stained from “animal or insect activity”. No semen or blood was found on the tracksuit bottoms.

DNA tests of semen from condoms and a condom wrapper at an area nearby were found to be associated with an unidentified male.

Dr Casey was asked to consider the potential length of time they had been there and he said that over time they would begin to discolour.

“Both were unrolled, in good condition, with no obvious signs of weather or degradation,” he said. He agreed therefore that they were more likely to have been “discarded recently”.

Dr Casey also examined the spade which was recovered from near where Ms O’Hara’s remains were found. There was no blood on it. The handle, he said, was examined for skin cells.

These tests revealed a low level partial DNA profile for at least two people, but the amount of DNA recovered meant it was “unsuitable to further interpretation”.

Dr Casey agreed with Sean Guerin SC for the prosecution that the absence of biological material such as semen or blood may not be significant. “You had an extremely low expectation of finding any given exposure to the elements,” he said.

Also giving evidence on Thursday, Chief Superintendent Peter Kirwan, from garda headquarters, said he applied to telephone service providers for data on five mobile phone numbers, under the Communications (Retention of Data) Act 2011.

Conor O’Callaghan, a telecoms engineer with Vilicom Engineering Ltd, said the company worked with telephone services providers in Ireland and dealt with the data they retained.

He explained how “cells” on phone masts are used to connect a person calling to the person they wish to call. He said these cells provide “coverage footprints” over an area in their range.

Sean Guerin SC, for the prosecution, produced maps of coverage footprints from cells in areas including Roundwood, Stepaside, Shankill, Kippure, Ticknock and Fitzwilliam Street Lower. Mr O'Callaghan agreed a cell at Edmundstown Golf Course, Rathfarnham, had coverage that stretched up onto Kilakee Mountain. His evidence continues.

Ms O’Hara’s remains were found in forestry on Kilakee Mountain, Rathfarnham, on September 13th, 2013.

Ms O’Hara was last seen at about 5.45pm near Shanganagh Cemetery in Shankill, Co Dublin, on August 22nd, 2012.

Her remains were found in a forested area on Killakee Mountain, Rathfarnham, on September 13th, 2013, by a woman walking her dog.

The trial continues in front of Mr Justice Tony Hunt.

Colin Gleeson

Colin Gleeson

Colin Gleeson is an Irish Times reporter

Fiona Gartland

Fiona Gartland

Fiona Gartland is a crime writer and former Irish Times journalist