Mystery Puzzles

After death of a rich old man, his children are surprised to know that he has left all of his money to his oldest son Jacob, who loved him dearly, and ignored his other children, who hated him.

So, the funeral is a day or two later, and the other sons and daughters have decided to kill Jacob and take his inheritance. Since his father’s death, Jacob has taken to drinking, and they know that, at the wake, he’s going to be gulping down the liquor like it was nectar of the gods. So they decide to poison the drinks. One of the other sons, John, tends bar, and gets the poison all ready.

So Jacob comes up, crying and depressed, and orders a scotch on the rocks. John serves him one, and he chugs it down in two seconds. “Give me another.” Jacob gives him a second glass of scotch, which he also drinks in a matter of moments. The other siblings are puzzled…the poison is fast-acting; Jacob should be convulsing on the floor and retching his guts out. Finally, fifteen minutes later, a rather inebriated and very much alive Jimmy orders one last glass of scotch, but as John hands it to him, he changes his mind and leaves, sobbing. The other siblings come over to John, and wonder what’s going on. They talk about what could have gone wrong for a few minutes, and figure the poison’s harmless. So John sips the drink he poured for Jacob, and is pronounced DOA thirty minutes later.

Why did Jacob live ? (He had no immunity to the poison, he didn’t know it was coming, and the poison was obviously deadly.)