What is the ruling regarding a person who gives false testimony before the police or prosecution, without swearing an oath, in a matter that is before the courts, outside a judicial setting and only for informational purposes, and whose testimony was later proven false, whether or not any harm ensued?

This comes under prohibited false testimony which is one of the major sins. Even though the testimony was not given before a judge, it takes the same ruling because prosecution is the first step in the judicial proceedings, especially if this testimony has a direct bearing on the judicial ruling.

And Allah Almighty knows best