4.—The conditions referred to in section 2 of this Act in relation to an interception for the purpose of criminal investigation are—

(a) (i) that—

(I) investigations are being carried out F5[or the F6[Police Ombudsman]], or another public authority charged with the investigation of offences of the kind in question, concerning a serious offence or a suspected serious offence,

(II) investigations not involving interception have failed, or are likely to fail, to produce, or to produce sufficiently quickly, either or, as the case may be, both of the following, that is to say:

(A) information such as to show whether the offence has been committed or as to the facts relating to it,

(B) evidence for the purpose of criminal proceedings in relation to the offence,

and

(III) there is a reasonable prospect that the interception of postal packets sent to a particular postal address or of telecommunications messages sent to or from a particular telecommunications address would be of material assistance (by itself or in conjunction with other information or evidence) in providing information, or evidence, such as aforesaid,

or

(ii) that—

F5[(I) in the case of a serious offence that is apprehended but has not been committed, investigations are being carried out—

(A) for the purpose of preventing the commission of the offence, by the Garda Síochána or another public authority charged with the prevention of offences of the kind in question, or

(B) for the purpose of enabling the offence to be detected, if it is committed, by the Garda Síochána or the F6[Police Ombudsman] or another public authority charged with the investigation of offences of the kind in question,]

(II) investigations not involving interception have failed, or are likely to fail, to produce, or to produce sufficiently quickly, information as to the perpetrators, the time, the place, and the other circumstances, of the offence that would enable the offence to be prevented or detected, as the case may be, and

(III) there is a reasonable prospect that the interception of postal packets sent to a particular postal address or of telecommunications messages sent to or from a particular telecommunications address would be of material assistance (by itself or in conjunction with other information) in preventing or detecting the offence, as the case may be,

and

(b) that the importance of obtaining the information or evidence concerned is, having regard to all the circumstances and notwithstanding the importance of preserving the privacy of postal packets and telecommunications messages, sufficient to justify the interception.