They are wild black cherries, Prunus serotina. The ripe fruits are nutritious.

Are the Italian researchers discussing the same choke cherries found in North America (Prunus virginiana)? I can't imagine how the patiend described in that case got enough cynide to cause poisoning, unless she ate raw, unripe berries without removing the pits.

There is also a group of plants found here called Choke berry, genus Aronia (not closely related at all), as well as plants with Choke berry as one common name, Amur Cherry (Prunus maackii).

Choke cherry (Prunus virginiana)leaves are high in cyanide, released when livestock bruises and eats them. Horses appear to be especially vulnerable. http://cal.vet.upenn.edu/projects/poison/plants/ppchoke.htm