The Serious Crime Review Team had only eight staff at the close of 2015, compared to 15 members in 2013, official figures show.
The team, commonly known as the cold-case unit, is tasked with reviewing unsolved homicides and other serious crimes and provides assistance to local gardaí.
Cases include the murders of Raonaid Murray in Glenageary, Dublin, in September 1999, Irene White in Dundalk, Co Louth, in April 2005, Emer O’Loughlin in Tubber, Co Clare, in April 2005, and Eddie Fitzmaurice in Charlestown, Mayo, in May 1998.
The team is also reviewing the high-profile disappearances of Deirdre Jacob, in Co Kildare in July 1998, Fiona Sinnott, in Co Wexford in February 1998, Jo Jo Dullard, in Co Kildare in November 1995, Fiona Pender, in Co Offaly in August 1996, Ciara Breen, in Dundalk in February 1997 and Annie McCarrick, in Co Dublin in March 1993.
The cold-case unit has been praised for its work, which has led to progress, including breakthroughs, in cases. However, figures released by Justice Minister Frances Fitzgerald show a significant drop in staffing.
In response to a parliamentary question asked by Fianna Fáil justice spokesman Niall Collins, she said numbers fell from 13 in 2011 to 11 in 2012, rising to 15 in 2013. The strength fell to 14 in 2014 and to eight in 2015 — a cut of 47% since 2013.
Former detective sergeant Alan Bailey, who retired from the cold-case unit in 2011, said: “No unit will ever say they have enough, but, to give the commitment needed to conduct reviews, eight members isn’t enough.”
He said the eight included the officer in charge and that at least one member was resting on any given day.
“When I was doing it, I would go down the country to the station to do the review, to do it in situ. If anything arose you could ask people in the station. At least two people, if not three, would go down.
“Now, with only eight members, you could only do one or two reviews at any given time,” he said.
A Garda spokesman said there was a process in place to “increase numbers”.