You don't really want to catch the animal now, do you?
Hello Snowy
why not catch it in a live trap?
After determining where the cat belongs, the owner gets it back. But then he better make sure it doesn't poop in the garden anymore.
The owner is responsible. How he does that is his problem.
I can think of other methods to teach the animal not to poop in the garden.
Cat owners are strange creatures. Their animal causes damage and they say, I can't do anything about it.
Steven