The 16-year-old was shot in the head as she sat in a car with her boyfriend and a friend at Brookview Way in Tallaght on February 8, 2012.
Melanie McCarthy-McNamara was 16 when she was shot dead
A courts killer was caught with a mobile phone in his cell after officers conducted a general search of the jail, a court heard.
Daniel McDonnell (27) was sentenced to one month in prison when he appeared in custody before Judge David McHugh at Blanchardstown District Court.
The defendant, with a previous address at Brookview Lawn in Tallaght, admitted to possession of a mobile phone at Wheatfield Prison, Cloverhill Road in Clondalkin, on July 20, 2022.
The court heard the defendant had a number of previous convictions.
His defence said McDonnell was serving a life sentence. He had co-operated with authorities, the court heard.
McDonnell received a mandatory life sentence in 2014 after he was found guilty by a jury of killing teenager Melanie McCarthy-McNamara.
McDonnell had denied murdering Melanie, but he wrote two letters while in custody that were used as evidence.
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