Continuity mistake: Before Halleck eats the cursed pie, a fork appears next to the pie between shots.
Continuity mistake: The position of the gypsy changes after Billy hits her.
Continuity mistake: After Halleck hits the gypsy, she leaves no blood on the windshield, but in the next shot there is blood on it.
Answer: I believe strychnine is odorless, so a dog would not be able to smell it. At the same time, it apparently has a bitter taste, which would question why a dog would ingest it - but some dogs tend to "swallow" or gulp food without chewing it, so may not notice the strychnine's bitter taste.
KeyZOid