You can speak from a bit of a personal angle when answering this question, if you wish. Share with the interviewer what brought you to this career path and how you feel about your choice to become a Detective.
"Growing up, my grandfather was a Police Officer and my father was a Detective. I believe that police work is in my blood and it was such a natural choice for me. Even as a child, I knew that I was going to pursue a career as a Detective. I'm very proud of my work and the path that I have taken."