19.—(1) As soon as practicable after it has received a specimen forwarded to it under section 18, the Bureau shall analyse the specimen and determine the concentration of alcohol or (as may be appropriate) the presence of a drug or drugs in the specimen.

(2) Where the Bureau receives 2 specimens of blood so forwarded together in relation to the same person or 2 specimens of urine so forwarded together in relation to the same person, it shall be sufficient compliance with subsection (1) for the Bureau to make an analysis of and determination in relation to one of the 2 specimens of blood or (as may be appropriate) one of the 2 specimens of urine.

(3) As soon as practicable after compliance with subsection (1), the Bureau shall forward to the Garda Síochána station from which the specimen analysed was forwarded a completed certificate in the form prescribed for the purpose of this section and shall forward a copy of the completed certificate to the person who is named on the relevant form under section 18 as the person from whom the specimen was taken or who provided it.

(4) In a prosecution for an offence under this Part or under section 49 or 50 of the Principal Act, it shall be presumed until the contrary is shown that subsections (1) to (3) have been complied with.