Don't poison the dog, but give the dog ex-lax every other day. After a few weeks of shit in the house, the owner will get rid of the dog on his own.
I realize this is a year old thread, but I cannot help but wonder how did the whole thing end?
If you poison the dog, the owners may wonder what happened and get blood tests done at a vet (we had a dog die, and found out it was from a rare type of mushroom that shut down the dogs liver).
Now, if they do so and find out it was a type of poison, well...who do you think they are going to look at? I mean, there's no way they'd turn their suspicions to the neighbor who has visited them several times, and also called the city on them, right?
Dumb idea.
Don't poison the dog, but give the dog ex-lax every other day. After a few weeks of shit in the house, the owner will get rid of the dog on his own.