The senior garda officer leading the hunt for the killers of mother-of-two Baiba Saulite yesterday described the decision not to prosecute as "a surprise".
Det Supt Walter O'Sullivan said a garda file on the case was sent to the Director of Public Prosecutions (DPP) and had recommended a prosecution.
He pointed out that the office of the DPP was an independent body but it "came as a surprise" to him when it was decided not to press any criminal charges.
Det Supt O'Sullivan gave his views on the decision while giving evidence at an inquest into Ms Saulite's murder.
Coroner Kieran Geraghty said her shooting was a callous and brutal murder, which left her children without the love and protection of a mother.
Ms Saulite (28), of Holywell Square, Feltrim Road, Swords, was shot three times at close range by a lone gunman while smoking at the front door of her home with a friend on November 19, 2006. Her two sons, Ali Alexandre (5) and Mohammed Rami (3), were sleeping upstairs at the time.
Ms Saulite, who was originally from Latvia, was "specifically targeted" and gardai believed the person who shot her was contracted to carry out the hit by a third party, Det Supt O'Sullivan told the inquest.
"It was apparent from very early on that sinister and heartless persons of a serious criminal ilk were involved in the deliberate and violent taking of this young woman's life and that they had prepared well in order to do so," he said.
The investigation has reached a point where it could not progress further in the absence of new information, he added.
The jury at Dublin County Coroner's Court returned a unanimous verdict of death by unlawful killing.
The court heard the mother of two from Riga and her housemate Mudita Antane (53) were standing at the door of the rented house smoking cigarettes when Ms Saulite was shot at 9.50pm.
Ms Antane, who cried while giving evidence, said that she was standing beside Ms Saulite when she noticed a person in grey come from the right side.
"The first time I got to look at him he was in front of me and Baiba. I saw he had a gun. When he fired the first shot, I heard the bang -- I think I heard two shots, but I started screaming so I'm not sure it there was another."
Ms Antane, who said she did not see the person's face as it was dark, went inside and called to her injured friend to "come inside". Ms Saulite staggered inside, clutching her chest, before collapsing in the hall outside the kitchen door.
A friend of Ms Saulite's, Inese Grabante, had left the house just seconds earlier and also witnessed the shooting. Ms Grabante said as she walked to her car, she noticed a sallow-skinned man coming into the estate.
"He looked at Baiba for a few seconds and he took a gun out of his right pocket," said Ms Grabante in her statement. "He pointed it straight at Baiba. I heard three shots. Baiba and Mudite started screaming and this man ran back in the direction he had come from."
He jumped into an awaiting vehicle and left the scene.
When emergency services and gardai arrived, Ms Saulite was found dead on the hall floor.
A post-mortem carried out by State Pathologist Prof Marie Cassidy found the death was due to gunshot wounds to the chest and contributory gunshot injuries to the right arm.
The inquest heard evidence she was in fear of being harmed.
There were knocks to the door two times on the evening of the shooting, the last at 9.00pm but the door was not opened. Det Supt O'Sullivan said it was probably preparatory work for the murder.
"We know from our investigations she had a fear of a person or persons she had an association with who might harm her and for that reason she was afraid to open the door," Det Supt O'Sullivan said.
The persons suspected of plotting and carrying out the murder, along with those who knowingly assisted in any way or withheld information from the gardai, were arrested, detained and interviewed with a view to advancing the investigation, he added.