What it does
The Criminal Investigation Act 2006 (WA) (the Act) establishes a comprehensive statutory framework governing the exercise of investigative powers by police officers and prescribed public officers in Western Australia. At its core, the Act codifies, limits, and supplements the common law powers of constables (s.7(1)) while providing ancillary rules for the timing, manner, and recording of their exercise. It does not create new offences but supplies the procedural machinery for detecting, preventing, and proving them.
Part 1 contains preliminary provisions, including an extensive interpretation section (s.3(1)) that defines over 40 terms. Key concepts include "reasonably suspects" (s.4, an objective test based on the officer's actual grounds judged objectively), "thing relevant to an offence" (s.5, which extends to animate and non-material items such as distances or visibility), and "officer" (encompassing both police and prescribed public officers under s.9). The Act expressly preserves its relationship with other written laws (s.6) and the common law (s.7), stating that its provisions prevail in cases of inconsistency.
Part 2 supplies overarching rules that apply whenever any power under the Act is exercised. These include the times at which powers may be used (s.14, any time of day or night unless otherwise stated), the ability to obtain assistance (s.15), the reasonable use of force (s.16, subject to The Criminal Code Chapter XXVI), the use of trained animals (s.17), the establishment of roadblocks (s.18), and ancillary powers when stopping vehicles (s.19). Section 20 clarifies that a power to enter one place may extend to adjacent areas in multi-occupancy buildings or where necessary to reach the target. Forensic examination of things is defined broadly in s.21, while s.22 provides a mechanism for ascertaining gender and s.23 creates a presumption against consent to search or procedure that can be withdrawn.