You should have left them indoors. Cats are to be indoors not outdoors you are the protector. This crazy neighbor should be slapped. I am so sorry for sounding so harsh. The cop should have put the cuffs on both of you. One for letting your cats outs...
Maybe he needs his own litter box. I am a Siamese breeder I recommend you to try to retrain the cat by putting him or her in a room by his self with a litter box till he catches on. He may not like the litter maybe you should try a new kind. Keep it ...