Someone always deliberately pulls the dog to shit behind my window. What should I do?

If, as you said, someone deliberately led the dog here, it would be a human job, and other measures against dogs would be ineffective. You can ask your family to tell the man face to face the next time they bring the dog to pee, and ask him not to do that again next time. If the man is still like that next time, you can solve it through the property or the police station. This is called giving gifts first, then serving as a soldier.

However, I still tend to agree with babyfaceii's analysis. His method is feasible, you might as well try it first.