That depends on the state private investigator licensing laws for your state. In many states, the words ‘private investigator’ and ‘private detective’ are interchangeable, but in some states there actually is a difference in their accepted meaning.
For example, in New Jersey those who want to become a private investigator must adhere to the licensing laws as detailed in the Private Detective Act of 1939. The person who has the prerequisite investigative experience is called the ‘qualifier’ and when the New Jersey State Police Private Detective Unit issues the license, the qualifier is actually classified as a Licensed Private Detective. The owner of a licensed detective agency may hire employees, who when properly registered with the state licensing authority, the investigative employees are classified as a Private Investigator.
Historically, the profession of non-law enforcement investigations started back with Pinkerton in the late 1800’s. At that time the term “private detective” was the formal name and the outfit they worked for was called a “detective agency.” There were many movies and books that began using the “private-eye” moniker more and more. It was television starting in the 1974 with James Garner
in the Rockford Files that really brought the investigative profession into the limelight. The show also had a major influence on
most people using the private investigator title. The P.I. title became famous with the Magnum, P.I. television show featuring
Starting around 1960, many states did not want the public to confuse a private detective with that of a police detective. There has been a trend amongst many state licensing authorities and state investigative associations to use the title ‘private investigator’ as compared
to ‘private detective’. In fact, many have actually taken legal steps to stop using the “detective” title.