Why are both the study of victims of crimes and debating called forensics?

Forensic science is the study of crime-related data, and is so-called because the results are to be used in a court trial. The word 'forensic' derives from the Latin forensis, law court. So forensic debate would be debate in a law court.

The word "forensics" derives ultimately from "forum", the central square and meeting place of the city. In that place debate of both intellectual and lega forms took place. The former led to the use of "forum" as an area for discussion, the latter to "forensics" as "related to courts" - which took place, initially, in the forum. It is interesting to note therefore that the most dominant (and thus presumably important) feature of legal trials is that they took place in the forum i.e. in public view.

Thank you. That all makes sense.