The 12 hour period runs from the time of your arrest but you may agree to a rest period between 12 midnight and 8 am and this will not be included in the 12 hours. In general, if you are arrested you do not have to say anything.However, if you are detained under the Criminal Justice Act 1984 you must tell the Gardai your name and address. The Gardai have no general power to take fingerprints or make forensic tests.he 12 hour period runs from the time of your arrest but you may agree to a rest period between 12 midnight and 8 am and this will not be included in the 12 hours. In general, if you are arrested you do not have to say anything.