Gardaí now believe the man who murdered a teenage girl, Niamh Murphy, in a derelict house in Ballsbridge, Dublin, on May 10th was known to her.
The man, who is in his 20s and has alcoholic and psychiatric problems, has already been questioned by detectives and is under surveillance.
Detectives have questioned a number of vagrant people who stayed in the derelict house on Pembroke Road and are satisfied that there is no threat of a repeat murderer stalking the city centre.
They believe the man had known Niamh for some time, but the reason he murdered her is not yet clear.
Niamh (17), originally from Salthill in Galway, had been living rough for about two years after running away from home. She spent time with a group of alcohol- and drug-abusers in Galway and was involved in petty crime on their behalf. At one stage she was arrested for trying to pass a forged cheque.
She moved to Dublin last year and again fell into the company of vagrants living around the city centre. She was not addicted to heroin but had developed an alcohol problem.
In recent months she had been staying on and off in the derelict and squalid house on Pembroke Road, opposite the American embassy.
On Friday, May 10th, she was murdered with an old pair of garden shears from the house. One of the blades was used to cut her throat.
Since then gardaí have been building evidence of her murder from forensic examinations of the scene and by interviewing other men and women who stayed in the house in recent months. Final post-mortem tests are still awaited. Sources close to the investigation said there was no sign of a sexual assault.
Niamh had problems settling in any normal form of accommodation. Her family tried to provide her with help on many occasions, and she was offered hostel accommodation by the social services but refused it. She preferred to live rough and begged in the city centre.
Gardaí said she was one of dozens of teenagers living rough in the city centre. Most have drug or drink problems and come from broken homes.
However, some like Niamh, who was an adopted child, come from caring families unable to prevent their slide into dereliction.
The man suspected of Niamh's murder comes from a very disturbed background. His extended family includes several figures with drug and alcohol problems and with involvement in crime. He has been living rough in the city centre for a number of years and has a criminal record.
The house is one of several locations in Dublin used by homeless people. It is owned by a Dublin property firm which has plans to redevelop it either as apartments or offices. It has lain derelict since the mid-1970s. Homeless people who have stayed there accessed it through a broken back gate on to a lane.