Since the police are being so helpful
Aren't there any animal groups or a dog warden or ASPCA that maybe more willing to help with the proof you have? Someone with an interest more of animals.
I really don't think the police will help you with any amount of proof you may get. IMO
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Rhonda, Bailey, Josie and my angel Bella Rue'
"Until one has loved an animal, a part of one's soul remains unawakened."
~Anatole France~