What is the Difference between police investigation and police intelligence?

A police investigation is conducted by sworn law enforcement officers and is done within the constraints of Constitutional laws. The investigation is conducted to determine if a crime has been committed, to determine who committed the crime, and to gather enough evidence to present to a prosecutor for a trial.

A private investigation is conducted by a professional investigator who is in all other aspects, a private citizen. Being a private investigator, several of the constraints of the Constitution do not apply (such as a Miranda warning before giving a statement). Private investigators are not restricted to criminal investigations. PIs work for clients who may request any manner of work, including infidelity investigations, background investigations, asset location investigations, or fraudulent insurance claims. PIs may uncover criminal violations, but are not bound by law to report them to law enforcement. PIs work at the behest of their clients.