The authority of police to establish and protect a crime scene flows from Section 129(a) of the Criminal Code, which makes it an offence for anyone to obstruct a peace officer in the lawful execution of his or her duty. Although the section does not specifically mention crime scene security, establishing a crime scene and protecting its integrity by refusing to allow people access, it is a legitimate part of an officers’ duty to investigate crime.

Temporarily restricting individuals’ liberty, by controlling access to a crime scene, is justified if the two criteria in the so-called Waterfield test are met. The test, which was set out in the English case of Waterfield (1963) and which is used to determine the common powers of the police, prescribes a way for a court to determine whether the exercise of a power not specified in a statute, sometimes called an “ancillary” power, or a power that arises out of a police officer’s fundamental duty, such as the duty to investigate crime, was justifiable in a particular circumstance