Reasonable and Probable Grounds
Reasonable and probable grounds — sometimes called "reasonable grounds" — is the legal threshold for many investigative powers in Canadian criminal law. The standard is required before police can: arrest without warrant under section 495 of the Criminal Code; obtain a search warrant under section 487; make breath demands for evidentiary samples under section 320.28; obtain wiretap and production orders; and exercise other significant statutory powers. The standard balances investigative effectiveness against Charter protection of liberty and privacy.
What the standard requires
Reasonable and probable grounds has two components: subjective belief — the officer must actually hold the belief that the grounds exist; and objective justification — a reasonable person standing in the officer's shoes, with the officer's training and experience, would also hold the belief. The Supreme Court's leading case is R v Storrey, 1990, which set out the two-part framework.
Where the standard sits
Reasonable and probable grounds is more than reasonable suspicion (the lower threshold for some investigative powers, including investigative detention and ASD demands) and less than proof beyond a reasonable doubt (the trial standard). It is approximately equivalent to a credible-based probability — meaning the officer must reasonably believe the proposition more likely than not, supported by evidence rather than mere suspicion.
How it's applied
Courts assessing reasonable and probable grounds look at the totality of the information available to the officer at the time, not in hindsight. Factors include: information from credible sources (witnesses, complainants, other officers); physical evidence at the scene; the officer's observations of conduct, demeanour, and surroundings; the officer's training and experience; and any corroborating circumstances. Information from anonymous tipsters carries less weight unless corroborated.
Charter implications
Where police act without the required grounds, the resulting actions are unlawful and engage Charter rights — section 8 (unreasonable search and seizure), section 9 (arbitrary detention), and section 10 (rights on arrest or detention). Evidence obtained as a result of the breach can be excluded under section 24(2) using the three-part Grant test. Successful grounds challenges are frequent and consequential in defence practice.
Strategic role
Challenges to reasonable and probable grounds are a foundational element of Charter defence work — particularly in drug, firearm, and impaired driving cases. Mass Tsang's criminal lawyers review every grounds determination carefully, looking for gaps in the officer's information, errors of fact, or improper reliance on stereotypes or generalizations.
Related glossary terms
