Key Legal Principles
A peace officer may arrest without warrant a person who has committed an indictable offence or who, on reasonable grounds, he believes has committed or is about to commit an indictable offence (section 494(1)(a) Criminal Code).
An arresting officer must not only subjectively believe that he or she has reasonable and probable grounds for the arrest, but that those grounds must also be justified on an objective basis, as seen from the perspective of a reasonable person standing in the shoes of a police officer with comparable experience to that of the arresting officer. See R. v. Storrey,  1 S.C.R. 241, at p. 249-50; R. v. Tran, 2007 BCCA 491, 247 B.C.A.C. 109, at para. 12.
Police officers may form the grounds for arrest based on information received from other sources (thus, hearsay may form the grounds for arrest).
In assessing the objective grounds for the arrest, the court must take into account the nature of the information taken in the context of the totality of the circumstances relied upon by the arresting officer.
Appellate Review of Reasonable Grounds for Arrest
The existence of reasonable and probable grounds is anchored in the factual findings of the trial judge and entitled to deference. Whether those facts amount at law to reasonable and probable grounds is a question of law and reviewable on a correctness standard: R. v. Shepherd, 2009 SCC 35,  2 S.C.R. 527, at para. 20.
Where the Grounds for the Arrest are based on an Informant’s Tip
Where the information or part of the information relied upon to establish the grounds for arrest comes from an informant, the legal test set out by the Supreme Court of Canada in R. v. Debot (1989), 52 C.C.C. (3d) 193 (S.C.C.) applies.
It is as follows:
i) whether the information received was compelling;
ii) whether the source was credible; and
iii) whether the information was corroborated in other respects by the police.
Each factor does not form a separate test. Rather, it is the “totality of the circumstances” that must meet the standard of reasonableness. So, for instance, where the police rely on an anonymous tip or on an untried informant, the quality of the information and corroborative evidence may have to be such as to compensate for the inability to assess the credibility of the source.
The recent gloss provide by the Court of Appeal for Ontario is that where such a tip is not compelling or credible enough on its own to justify an arrest it may provide “the initial tableau of information” against which other information obtained by police may be assessed, based on the arresting officer’s experience: see R. v. Anang, 2016 ONCA 825.