Well it looks like one of the nightshades - did your father in law grow this deliberately, or did it pop up on its own? As for whether its atropa belladonna (toxic) or Solanum nigrum (eaten in some parts of the world, but generally considered toxic, mostly because of differentiating between it, Atropa and Deadly nightshade), it would have been useful to have seen the flowers.

It's not Atropa belladonna. Deadly nightshade has single berries not clusters. I'm inclined towards Solanum nigrum. The clusters of berries look very much like Solanum dulcamara, woody nightshade, but black instead of red.

Still wouldn't recommend eating the berries...

And how about a real outside guess, Huckleberries?
Still would not recommend eating them though, just in case.