Get a degree in any area that you are interested in. It doesn't have to be directly related to sociology or Law. Apply to become a member of the Garda Reserve Gather life experience by travelling before you join.
The Investigative person will usually find a particular area of science to be of interest. They are inclined toward intellectual and analytical activities and enjoy observation and theory. They may prefer thought to action, and enjoy the challenge of solving problems with clever technology. They will often follow the latest developments in their chosen field, and prefer mentally stimulating environments.