Forensic psychology and policy (101-style questions)

TLDR:

• Do forensic psychologists ever take the stage with their data to influence policy? Is that rare
• What spheres of influence do forensic psychologists take part in in the criminal justice process?
• What is risk assessment? e.g. is it a data-driven, empirical arm of criminal justice? e.g. gathering a large corpus of cases, diving into common denominators and pulling the factors that matter.
• What's a good case in favor of punishing misdemeanors and petty offenses w/ arrest, prosecution, etc? In the big picture, it can reduce crime and make the public safer. Has anyone in forensic psychology ever successfully argued against a statute?

I am a 101 at this, so feel free to fire off basic stuff or correct / clarify misunderstandings you think I may have, I won't mind if you link to broken windows policing on Wikipedia, cite a favorite textbook.