You’re talking about the legal system. Our laws are pragmatic, and account for things like lying.

OPs post is a philosophical question. The premise is whether it’s moral for you to fuck roadkill based on whether you killed it or now. Concerns like lying to a courtroom or to the people around you, are out of scope.

So philosophically:

them doing it intentionally and claiming it was an accident

This would be immoral, since they still killed the animal to fuck it.