There aren’t really any distinctive features we can use to reliably distinguish berries that are poisonous so your best bet is to build up a thorough knowledge of plants or a good guide. Some people advise against eating berries that are white or yellow, or that grow on vines, because they say these are typically bad for you. Most purple, blue or black berries, however, are said to be okay. Yet grapes grow on vines while deadly nightshade berries can appear purplish-black and are highly toxic. The best rule is not to eat the fruit of any wild plant unless you know for sure that it’s safe.
Answered by Mike Simpson.