@Yog When it comes to street level crime the police are more hampered by a lack of knowledge then power. A well trained mortal with a gun able to call backup is actually fairly threatening to most street monsters. The problem is escalation. Most street level monsters answer to some higher power who the cops can't deal with.
Basically if we empower SI and organize them it turns into a war rather than just better policing.
Edit: To be clear maybe we can empower them enough to win that war, but it would be a war. Unless say we use a fairy favor to get a Queen to publicly acknowledge that Mortal police have the authority to enforce mortal law as they are charged to do my the taxes payers.