THE victims of a double murder in Limerick both died from "catastrophic" single gunshot wounds to their head areas, the jury in a trial has heard.

State Pathologist Professor Marie Cassidy told prosecuting counsel Brendan Grehan SC that Desmond Kelly, in whose house the double shooting took place, was shot "at close range in the right temple area of his head".

She said the second victim, Breda Waters, who was found in an upstairs bedroom, died as a result of a single gunshot injury to the neck area.

It was day three of the trial of first cousins Patrick O'Brien (31), of Glanntan, Golflinks Road, Castletroy, Limerick and Thomas Stewart (28) of The Cedar, Briarfield, Castletroy, Limerick who have both pleaded not guilty to the murders of Mr Kelly (23) and Ms Waters (28) on January 9, 2011, at O'Malley Park in Limerick.

Prof Cassidy said she visited the scene the day after the shootings and located Mr Kelly lying on the kitchen floor in a pool of blood on his left side with his hips and knees bent.

"There was a large shotgun wound to the right temple area and as there was gun residue and soot surrounding the area, the shot was fired at fairly close range," said Prof Cassidy.

She said Mr Kelly collapsed and died immediately and there was no sign of any struggle.

She said she located an exit wound on the left side of the head and there was blood and tissue splatter on the walls and cupboards.

She said Mr Kelly was dressed in a dark blue dressing gown and blue boxer shorts and wore rosary beads around his neck.

She said Mr Kelly had no drugs nor alcohol in his system at the time of death and was an otherwise healthy person.

Prof Cassidy told counsel she found Ms Waters lying on her back on a bed in a front, upstairs bedroom.

"It would appear she was standing up and collapsed back onto the bed when she was shot in the neck," she said.

"There was a large gaping wound to her lower neck area and she wore rosary beads around her neck," she added.

She said because there was no apparent gunshot powder residue at the wound it would appear Ms Waters was not shot at close range but by someone standing a few feet away, possibly in the bedroom doorway.

She said there was no exit wound and clusters of bullet pellets were found in her upper neck spine and jaw line and her lower jaw was fractured.

"There was no evidence of any other injuries to Ms Waters and she was a healthy person prior to her death," added Ms Cassidy. "There was also no alcohol in her system but traces of therapeutic tranquilisers in her system."

She said there was also no evidence of a struggle and Ms Waters died as a result of a single gunshot wound to her neck.

"Both injuries were catastrophic," she said.

Ballistic expert Janet O'Neill, who attended the scene gave evidence that the front door did not seem capable of being locked and there was no presence of a firearm at the scene.

She examined a discharged gun cartridge found at the scene and concluded it was a 12-gauge, English-manufactured BB shot size suitable for a 12-gauge shot gun.

She said the discharged gun cartridge found near Mr Kelly's body was consistent with the cartridge found on the stairs but that an A-shot size bullet was found in the body of Ms Waters.

The trial continues before Mr Justice George Birmingham and a jury of six men and six women.