You would need to complete a 4-year college degree, then 3 years of law school, and passing a written bar examination. During the first or year and a half, law students study core subjects, then they specialize in their favorite field of law like Criminal Law. For details see the link below:
www.bls.gov

 When a society and its government come up that certain behaviour is evil to
citizens, or damaging to the society as a whole, such a thing is considered as
c crime and is made punishable by sanctions such as fines and imprisonment.
Most crimes are noticed in statutes that have been enacted by federal, state,
and local government legislatures, in response to issues that affect the
jurisdiction. For example, a city may determine that it is a crime to be drunk
in public, while the federal government decides bank robbery is a federal
crime, since most banks are federally insured. So I recommend you go for it
because it is good.