Alcoholic intoxication is one of the biggest reasons why the Director of Public Prosecutions does not prosecute in alleged rape cases, according to a new report by the DPP’s office.

The DPP’s latest report shows that in the vast majority of alleged rape cases no prosecution is mounted as there is insufficient evidence, the Irish Times reports.

Where cases were not prosecuted for insufficiency of evidence one of the main reason was that the complainant was intoxicated, and could not recall clearly the alleged offence or the details of it.

According to the report, in 58 per cent of cases either the complainant or the suspect were intoxicated at the time of the alleged offence.

Questions also arose concerning whether the complainant’s account was credible and reliable.

Another leading factor in the failure to prosecute was delay in making a complaint, which arose in almost 10 per cent of non-prosecuted cases. Such delay could mean a lack of medical or forensic evidence due to lapse of time.

The report contains the results of a survey of rape files in the office, where 800 such files were examined.

A detailed examination of all files relating to 2005, a total of 296, was carried out, as files originating in this year, if proceeded with, were likely to have gone through the courts, including appeals.

The research found that the majority of complainants, 93 per cent, were women. One in four of all complainants was under 18 at the time of the alleged offence. The research included offences of unlawful carnal knowledge of under-age girls and boys.

Complainants withdrew their complaint in 17 per cent of the cases, usually before the file reached the office of the DPP.

This figure was lower than in the earlier research, and was probably explained by the inclusion of child victims, who are much less likely to withdraw a complaint. In one per cent of the cases withdrawn complainants admitted making a false allegation.

Introducing the research, DPP James Hamilton said that rape offences were very serious, and in all cases it was necessary to prove that the complainant did not consent, and that the suspect knew he or she did not consent or was reckless as to whether there was consent.

All elements of the offence must be proved beyond a reasonable doubt to prosecute successfully.

The overwhelming majority of cases occur in a private location with no witnesses, and most allegations relate to a suspect known to the injured party.

In 35 per cent of files referred to the DPP there was a decision not to prosecute. The main reason for a decision not to prosecute was insufficiency of evidence. In about a third of cases the prosecution went to the District Court, and in the remainder was on indictment to the Circuit Criminal Court or, in the case of murder or rape, the Central Criminal Court.

The report shows a slight fall in the number of acquittals, to 2 per cent in 2009, down from 4 per cent in 2007.

Almost a third of the 2009 files have yet to be heard. Of the cases brought to trial, 97 per cent resulted in a conviction, including 94 per cent following a plea of guilty. The number of files dealt with by the office has more than doubled since Mr Hamilton took office, from 7,321 in 1999 to 15,952 last year.