I have a bush in my back yard, and have also encountered a similar VERY large bush while walking my dog. The berries look for all the world like what we called "wacholder" in Switzerland, perhaps even "Weintrauben." The berries are small, maybe 1/2" in diameter and grow in large clusters with reddish stems connecting to the main shrub. The actual clusters of berries are more or less flat. The leaves are simple oblongs in shape. I know we made jam out of something very similar in Switzerland while I lived there years ago, but have no memory of the appearance of the shrub. I don't want to harvest these berries to make jelly and end up discovering that they are poisonous.

I don't think I've seen black currants in which I'd describe the clusters as flat.

Black currants have a distinctive taste and smell. Just crushing one and smelling it should be enough, shouldn't it?

Hmmmmmm not at all like what I have in my yard and seen elsewhere.... Am very curious as to what they could be. Will try to post a photo to see whether anyone recognizes what they might be. Thanks for the info!

Aronia maybe?

Google 'aronia', then select 'images' from the menu in the upper left hand corner.

If they are ‘Aronia,’ -- the following discussion was interesting:

viewtopic.php?f=1&t=5009

Google: Black Elderberry

Black, red, green Flat clusters are elderberries Sambucus spp