"Public" data is rarely open or publicly available,
and when it is, it's usually not easy to use.
how many people have a criminal record
how many people have served time in prison or jail
how many children are on some type of supervision or probation
how many juveniles become adult offenders
how often people reoffend after release
how many shootings there are in America
how many police are investigated or prosecuted for misconduct
how many people in America own guns
how often police stop pedestrians or motorists
how many incidents of domestic violence are reported to police
what percentage of those eligible for parole are granted release from prison
how many corrections officers are disciplined or prosecuted for abusing prisoners
how many criminal cases are referred to prosecutors and how they decide which to pursue
Federalism
Broad suspicion of transparency
Lack of will
Pick up the phone
Go to the courthouse
Get the piles of paper
Liberate the PDFs
Make your own data that answers the questions you have.