If you're looking to check off all of the careers in Bitlife then one of those you're going to need to do is becoming a detective! We'll walk you through exactly what you need to do to become a gumshoe and solve yourself some crimes along the way. It's not too difficult of a process, but it does require a bit of know how to complete the challenge.
BitLife Detective Guide
Becoming a detective will first require that you head down the track to becoming a lawyer. So, you will want a character that has high smarts. If you get one that isn't so smart, just start a new life and try again. You're looking for around 70 or so, which you can improve overtime. Once you've got your character, age it up until you can head to the library and read books. You can do both of these each year to increase your smarts. You will also want to study harder in school each year as well!
Once you're in High School, it's time to really buckle down. Join at least two extracurricular activities and study each year. You want to do this because you can get a scholarship to university this way. Once you've graduated, you will want to head into a major that will align with going to law school. Something like political science should work. If you don't see one of these options then skip a year and try again.
You'll want to do the same thing in University as you did in High School, and join activities and study hard. Once you graduate, apply for Law School and go for the scholarship. You don't have to study harder in Law School, because there's no real additional benefit.
Once you graduate from Law School, you should become a Junior Clerk. Work harder each year and keep an eye on jobs. If something comes up that will allow you to join the police force, then you should take the job there. Once you've gotten a job with the cops, then you will again want to check the jobs each year to see if Jr. Detective comes up! Once you find that option be sure to apply. You will then need to make it through a few years and working hard to get promoted.
Once you've become a detective, you will have to keep going through the ages for about 10 or so years before you are credited with obtaining the detective career! Just don't do anything crazy to lose your job before then or you won't get the checkmark.