Criminal law focuses on behaviors that are sanctioned under criminal code and defined as illegal. Prosecutors and District Attorneys sanction illegal behavior, while criminal defense lawyers represent clients accused of criminal activity. Both prosecution and defense professionals deal with issues of individual liberty, basic rights, and responsibilities. In some Common Law countries other than the U.S., and in most Civil Law countries, the roles of a prosecutor (or procurator) and defense lawyer (or advocate) are separated more clearly into different professional specialties.
Read more at:
National Association of Criminal Defense Lawyers