Canadian policing has been strongly shaped by British and American forms of policing. Explain four ways Britain and the United States have influenced Canadian policing subculture Pragmatism. officer's "working knowledge"; for example, part of a police detectives' working knowledge is their ability to decide which cases contain enough information to lead to an arrest and are worthy of further investigation and which will likely lead to dead-ends and The "Fruit of the Poisonous Tree" legal doctrine is used to exclude illegally obtained evidence,.