Q. If a Jew appears to have committed a crime, such as possible sexual abuse, why doesn’t the Beth Din deal with him/her?
A. The rabbinic sages were adamant that Ex. 21:1, “These are the mishpatim which you shall place before them”, requires that legal matters – mishpatim – should be handled by Jewish courts. This was for both nationalistic reasons and because the Jewish doctrine of justice was superior to that of other nations.
Over the centuries Jewish communities often enjoyed relative judicial autonomy (handling even criminal cases, laying down punishments and maintaining their own Jewish prison system), and on the whole the results were highly impressive.
However, we have a rule of dina d’malchuta dina (“The law of the land is the law”) which means that in matters in which the state has an inherent concern, e.g. taxation, we do not purport to override or circumvent the state legal system.
These days we have no hesitation about leaving criminal matters to the secular courts. We place no credence on emotional outbursts like “Do you really want to hand over a fellow Jew to the goyim?” Such statements reflect bitter experience of gentiles, but in a modern, democratic state they have no relevance. The police and the authorities who deal with criminal law are not “the goyim”; they are the citizenry and the due processes of law, with Jewish lawyers amongst the legal brains.