Thomas Dalton wrote:
"In the Cardassian legal trials are entirely a formality and only have a ceremonial function. The verdict is determined long before the actual trial is held. The person prosecuted learns what he or she allegedly committed at the trial."
Which is a generalisation based on a single episode. Is it universally true? Do we care?
It could be written better ("In Episode X a Cardissian legal trial is shown to be entirely a formality..."), but the episode is a valid source.
The episode would be a valid source for how Cardassian law was applied in that episode, but even in fiction one should resist the temptation to generalize. Such bad habits could too easily be adapted to the real world. If the episode makes a specific statement about Cardassian law that would be an entirely different matter. "Shown to be" can be problematic because it can harbour a veilled POV.
Ec