This murder case was the first trial in Ireland where there was only DNA evidence, writes Carol Coulter, Legal Affairs Correspondent
Future prosecutions that include DNA evidence are likely to be accompanied by other evidence, either statistical or corroborative, following yesterday's direction to the jury to acquit a man accused of murder.
This followed five arguments from the defence, centred on the lack of any evidence other than DNA against the accused. The first, rejected by the judge, was of an essentially technical nature, and argued that the prosecution had not proved that the accused did not have a twin, who would have had the same DNA.
The second, also rejected, was that an eyewitness had described a probable assassin who was of different build than the accused. No evidence was brought forward by the defence as to what build the accused had at the time of the murder.
The third argument concerned the fact that the forensic scientist in the case had accepted that the head of forensic science in the UK had stated an accused should never be convicted on forensic science alone. Mr Justice Butler regarded this as essentially an opinion and did not base his direction on it.
However, he took into consideration two other points: that the forensic scientist had no qualifications in statistics, and therefore in the evaluation of the probability of identical DNA coming from another person; and that the prosecution had not disproved the possibility that the accused had a brother, who could possibly have had identical DNA. There is general agreement that brothers have a one in 10,000 probability of identical DNA, while the probability for strangers runs to billions.
This is the first case in Ireland where there was no evidence at all other than DNA evidence, and it is therefore very unusual. If it does happen again, it is likely the DPP will bring forward statistical evidence to deal with the question of probabilities.
The DPP will be examining the transcript in this case, according to sources in the DPP's office. It is open to the DPP under the 1967 Criminal Procedure Act to appeal a question of law to the Supreme Court, where a trial judge directs the jury to acquit.
However, this section of the Act does not apply to an evaluation of evidence. The proposal in the planned Criminal Justice (Garda Powers) Bill to increase the powers of gardaí to obtain DNA will also go ahead, according to a spokesman for the Minister for Justice.