I am informed by the Garda authorities that formal identification parades are the main way identification of a suspect by a victim or witness is tested prior to court. Instructions issued to every member of An Garda Síochána set out how, based on established best practice and case law precedent, a parade should be conducted. At present this process does not involve a two-way mirror.
The current procedure used by An Garda Síochána was introduced following advice from the Law Officers. In order to ensure that there is no doubt as to the person the victim or witness has identified, it is necessary that a clear identification is made. This may be done in a number of ways, including pointing to or stating the position of a person on the line-up or stating a number assigned to them. Prior to this the procedure necessitated the witness or victim placing their hand on the shoulder of the person as part of the identification process.
The conduct of identification parades generally is an issue I am reviewing at present with a view to seeing what improvements, if any, might be made, including the possibility of making the procedure less traumatic for victims or witnesses.