What is the test for reasonable and probable cause?

There can be no dispute that a consideration of whether or not reasonable and probable cause for a prosecution existed at the relevant time involves both a subjective and an objective analysis, as is necessary when considering the lawfulness of an arrest. It is further the case, based on Oniel v. Toronto, that reasonable and probable cause must be considered from various points along the investigative time-line. In other words, even if there were reasonable and probable grounds to make an arrest, in certain cases, additional information may be obtained that may vitiate the original grounds. In those circumstances, continued detention or prosecution would establish this third element of the tort.