Staff at the State's forensic science laboratory will refuse to take any new cases from March 4th because of "a massive and growing backlog", according to the IMPACT trade union.
Forensic staff voted by 37 to nine last week in favour of industrial action, with a turnout of 98 per cent.
An IMPACT official, Mr Ray Ryan, said yesterday the industrial action could escalate after March 4th. This may take the form of staff analysing current cases, but not certifying the results, making them unusable in court.
The union says 52 professional and technical staff in the laboratory are now dealing with nearly 9,000 cases, more than 5,000 of which have been delayed by more than six months, which renders forensic evidence useless in some criminal cases.
Sexual offences, drug offences, armed robberies and other violent crimes are among the types of cases which will be delayed, says the union.
IMPACT is calling for the immediate implementation of a report by independent consultants Deloitte and Touche, which said staff numbers at the laboratory had not kept pace with growing caseloads.
Sources said yesterday that staff were constantly under "phenomenal pressure" to process cases. The report, published last March, recommended that 17 extra technical and professional staff be added.
Mr Ryan also pointed out that the "Northern Ireland forensic laboratory has about 130 staff for a population roughly half ours".
The consultant's report also recommended an improved career structure to retain and motivate staff, and that forensic scientists should be paid on the same pay scales as other scientists in the civil service.
A new organisational structure, better facilities, and the establishment of a national DNA database for convicted criminals were also recommended in the report.
A spokeswoman for the Department of Justice said yesterday it did not comment on industrial relations.
Fine Gael's spokesman on justice, Mr Alan Shatter TD, said that the "failure of the Minister of Justice, Mr O'Donoghue, to recruit new staff at the laboratory is allowing many drug dealers to walk free because drug samples cannot be analysed in time for prosecutions to be brought."