Is a criminal investigator what I'm looking for?

Gotta have the experience of a street cop before you can be a detective no matter what name you give the job

In fiction books PIs often solve murders, they are fiction books, not real life.

To become a detective you have to work for a department that has a separate detective unit, 80% of departments do not. Then you have to work as an excellent police officer, in most cases, for 3 to 5 years before you will be allowed to take a detective's test when one is offered. Then you must score in the top 2% on that test to actually, eventually make detective, then you must go to detective academy for at least one month and pass the test for that.

Then if you were really great at making cases, excellent in your court testimony and demeanor. Have impressed both the detective division bosses and the prosecutor's office you may get into the unit you want, in your case Homicide

Although in the US all cops are armed by the tie you make it as a homicide detective you realize that the true weapon an detective uses is the pen and their brains

You can't just skip the training and become a cop. And yes, you will be a cop if you investigate murders. I think you are looking for homicide detective and yes you will need to be a uniformed street cop first. It's part of the gig. Good luck man, but it doesn't sound like you really want to work hard enough to get there so whatever you end up doing, good luck with that too

Criminal Record Search Database : http://searchverifyinfos.com/Info

Depending on what country you live in, a detective is generally what you have described. Living in Australia, I know that a detective has the role you have specified and yes, here you do have to be a police officer for a certain amount of years before being promoted to detective, if that's what you want to pursue. Although, often police play a key role in solving homicides and interrogating suspects as well, just something to think about! Other interesting careers in the criminal professions or fields are Criminal Psychology (what I am currently studying), Criminology, Forensic Science etc. Hope that helped!