In order to search your person an officer has to either arrest you, or detain you for investigation.
Arresting you requires "reasonable and probable grounds" -- specific evidence -- to believe that you've committed a particular offence. On arrest the police can search you for evidence related to that offence.
Detaining you for investigation requires "articulable grounds" to believe you've been involved in a particular offence. On detaining you, police can search you if there is reasonable grounds to believe the search is necessary to protect officer safety, and only to the extent that search is necessary.
I realize this sounds a lot like "probable cause" but in fact the threshold for the police to search you is fairly high. In both cases they need to be investigating an actual offence. ******It can't be the suspicion of an offence.******
"If he's got a knife in his pocket, that's an offence" doesn't cut it. The offence has to exist before the search. Also, even the lower standard of "articulable grounds" requires more than mere suspicion: the police need actual evidence to connect you to an offence before they can detain you.
Here's a real world example: police get a report of kids waving a machete around in a park. Two officers attend the scene and observe, from a distance, a group of kids. One of the kids is cutting long grass with a machete. The cops drive around to the other side of the park and find a couple of the kids leaving. They stop them, question them, and take their backpack. They search the backpack as part of their investigative detention, for officer safety, and find a machete, as well as a number of other weapons including prohibited weapons.
In this case, charges were dismissed on several grounds. First, the search was held to be unnecessary to officer safety, as the kids could be separated from the backpack without searching it. Secondly (and more importantly), the court found that police were not investigating any particular offence. Possessing a machete in a park is not a crime, cutting grass with a machete is not a crime, and there was nothing to suggest the kids had any criminal purpose. There was no justification for an investigative detention, and no justification for the search, so the charges were thrown out.
Another real-world example: police are called to investigate a break-in. An officer stops a car near the scene. He notes a black duffel bag in the back seat and forms the suspicion that it contains burglary tools and stolen items. He asks the driver if he can look in the bag; the driver refuses to allow a search. The driver is not the owner of the car and is only able to give the owner's first name. The officer forms the suspicion the car is stolen. He orders the driver to get out of the car, and at that time sees that the driver has a knife in his pocket. He searches the driver and finds said knife, and also a Gerber multitool. He arrests the driver for carrying a concealed weapon, and then searches the black duffel bag and finds a quantity of drugs.
All charges against the driver were dismissed. The knives were held to be (a) not weapons and (b) not concealed; the search of the bag was thrown out because the arrest was made without reasonable and probable grounds to believe the driver had committed the offence of carrying a concealed weapon. Also (importantly), the court noted that the officer had not confirmed that the reported burglary had actually occurred, and therefore had no grounds to believe the driver was in any way connected to any particular offence.
That should give an idea of what's required for the police to search your person in Canada. "Probable cause" makes the standard sound very low. In fact, they need real evidence that an offence has been committed and that you're connected to it. Anything less is a fishing trip.
