How can I tell if a mushroom is poisonous?
No as per: "There are no outward characteristics that all poisonous mushrooms have in common, so picking and eating wild mushrooms requires the utmost caution. To be absolutely safe, the only mushrooms you should eat are those found at supermarkets and restaurants!

All the old wives’ tales about how to tell if a mushroom is poisonous – such as whether it tarnishes silverware or turns blue when bruised – are dead wrong. 

There’s a saying that there’s no such thing as an old, bold mushroom hunter."