Proving a pet smell isn’t impossible, but it’s also not easy when you’re trying to withhold part of a security deposit to remedy a pet smell.
It has to be documented, and proven beyond normal wear and tear. Visible damage is evident and simple to prove. Smells are completely different. They cost more to remedy, and you may need to interview people in the home to document a smell.
Testimony recording multiple people walking through the home describing what they smell and where as they go through the home is a good practice.If you’re in doubt, go to a local courtroom to watch how things are handled. Since these things can be subjective, it’s good to know how a local judge and/or magistrate decides.