Around £30k was spent on the trial of two Lithuanian men, which collapsed after concerns were raised about translation by an interpreter.
It is understood other interpreters alerted the court when they voiced concern about the translation of evidence given by an alleged rape victim who is also Lithuanian.
The Justice Minister David Ford confirmed the matter is under investigation after the trial at Craigavon Crown Court was aborted last month.
The men were charged in connection with the July 2011 rape and imprisonment of a woman in her Lurgan flat and an attack on her ex-boyfriend.
Darius Porcikas (24) from Upper Edward St in Newry faces 14 charges including five counts of rape, two of sexual assault, two of false imprisonment, causing actual bodily harm and assault, all in relation to the woman. He also faces charges of causing grievous bodily harm in relation to her ex-partner. Vytaytas Mikulinas (23) from Birch Hill Park, Portadown faces a single charge of causing actual bodily harm to the ex-boyfriend.
To date £8k has been paid for interpretation in the case. Almost £9k has been paid out in legal aid and a further £7k on prosecution counsel in the case so far. The PPS said that, with the PSNI and Court Service, it had a joint contract with the Northern Ireland Council for Ethnic Minorities (Nicem) for interpretation services.
“This contract is managed by the Department of Justice and Nicem source and provide interpreters at the request of the PPS for prosecution witnesses,” said the spokesman.
“The circumstances of this trial are the subject of an ongoing inquiry and a retrial of the case itself and we will be unable to comment further until that inquiry is completed and until the case itself is concluded before the courts.”
Nicem said its business arm, Connect-Nicem, is responsible for interpretation services. Its director Gabrielle Doherty said the interpreter was qualified and had never before been the subject of a complaint. “The interpreter... is cleared to work with the criminal justice agencies.”