The number of homicides in the four years to 2013 fell by 5%, new figures reveal. Of the 83 homicides in 2013, proceedings were taken in 53 cases, with convictions in 23.
The CSO figures show there were 83 homicides in 2013, compared with 88 in 2009.
However, there was a 35% increase in sexual offences - mostly for rape and sexual assault. There were 2,010 sexual offences recorded in 2013.
The CSO has warned that these statistics should be interpreted carefully.
The figures showed gardaí detected* just over half of sexual offences and just one in five burglaries, 40% of which took place in the Dublin area.
The number of robbery, extortion and hijacking offences also increased, by 13%.
The figures, which cover 2009 - 2013 also show road traffic offences dropped by 47%.
*A crime that is "detected" includes ones where a summons or charge has been issued, or where resolution has been reached through the issuing of a caution or the enacting of a juvenile diversion programme.
The CSO said today a previous study indicated garda estimates of detection rates may overstate the actual detection rates by up to 16%.