139 Cautioning of persons
(1) For the purposes of section 138(1)(a), evidence of a statement made or an act done by a person during questioning is taken to have been obtained improperly if—
(a) the person was under arrest for an offence at the time; and
(b) the questioning was conducted by an investigating official who was at the time empowered, because of the office that he or she held, to arrest the person; and
(c) before starting the questioning the investigating official did not caution the person that the person does not have to say or do anything but that anything the person does say or do may be used in evidence.
(2) For the purposes of section 138(1)(a), evidence of a statement made or an act done by a person during questioning is taken to have been obtained improperly if—
(a) the questioning was conducted by an investigating official who did not have the power to arrest the person; and
(b) the statement was made, or the act was done, after the investigating official formed a belief that there was sufficient evidence to establish that the person has committed an offence; and
(c) the investigating official did not, before the statement was made or the act was done, caution the person that the person does not have to say or do anything but that anything the person does say or do may be used in evidence.
(3) The caution must be given in, or translated into, a language in which the person is able to communicate with reasonable fluency, but need not be given in writing unless the person cannot hear adequately.
(4) Subsections (1), (2) and (3) do not apply so far as any Australian law requires the person to answer questions put by, or do things required by, the investigating official.
(5) A reference in subsection (1) to a person who is under arrest includes a reference to a person who is in the company of an investigating official for the purpose of being questioned, if—
(a) the official believes that there is sufficient evidence to establish that the person has committed an offence that is to be the subject of the questioning; or
(b) the official would not allow the person to leave if the person wished to do so; or
(c) the official has given the person reasonable grounds for believing that the person would not be allowed to leave if he or she wished to do so.
(6) A person is not treated as being under arrest only because of subsection (5) if—
(a) the official is performing functions in relation to persons or goods entering or leaving Australia and the official does not believe the person has committed an offence against a law of the Commonwealth; or
(b) the official is exercising a power under an Australian law to detain and search the person or to require the person to provide information or to answer questions.
Expressions defined in the Dictionary are identified in bold print. Click here to access the Dictionary.
Continuity and change – moderate change
Cautioning of persons
‘Questioning’: s139(1), (2)
I do not believe that the word means 'a conversation during which questions are asked'. Clearly to my mind the section was aimed at formal or informal interrogation of a suspect by a police officer for the purpose of the officer obtaining information ... (R v Naa (2009) 76 NSWLR 271;  NSWSC 851 at ).
‘Under arrest’: s139(1)(a),(b); and see (2), (5), (6)
Communicating the caution: s139(3)
operates on the ability to understand the concept underlying the caution and the function of a caution. The caution is meant to convey to an arrested person that he/she has the right to choose to speak or to remain silent. It is meant to ensure that the person is aware that if he/she speaks, what he/she says may be given in evidence (R v Deng  NSWCCA 153 at  per Greg James J).
there is no such failure if a reasonable person in the position of the officer, acting with proper respect for the rights of suspects, did not and could not reasonably have been expected to perceive that the suspect did not understand the caution (R v Taylor  ACTSC 47 at ).
Significant other sections that are or may be relevant
Other sections include:
Last updated: 4 July 2017