NYPD Detective investigator and Specialist.?

NYPD gives many of those in specialized units the rank of detective, even though they do no detective work. Many other larger departments give specialists detective pay but do not call them detectives.

At the insistence of the detectives endowment associations (the detectives union) they call those others no investigation specialized detectives to differentiate.

As to street crime. You do excellent work as a patrol officer and if the commander of your precinct believes you can be trusted You can get on the street crimes unit for that precinct.

Detective specialists tend not to wear suits. Some are in uniform, many are in civilian dress.

Real detectives (investigators) wear suits also called conservative business attire.

One is a general duty investigator while the other has some form of speciality training like a unique degree such as computer sciences for a computer forensics detective position.

Both wear plain clothes but one is more or less stove piped into a speciality stream and the other is a generalist.