How are you going to determine if a trainer is cheating?
It's already known that not every illegal substance shows up on a test.
When you take the photos in the winner's circle, do you ask any questions?
Pacer2 uses the argument there's cheating in all sports, and the cheaters get caught, same goes for trainers. It's either being totally naive or stupid because as you say, not all illegal substances show up on tests.