Suppose you wanted to graffiti someone else’s fence without getting caught. The color of the graffiti isn’t important; it’s about sending a message. That means you can choose any color paint you want. Naturally, everyone in the neighborhood has access to the same colors (so no particular choice would draw suspicion) except for one: it’s a special, rare color that you are known for producing. You aren’t the only one who has any, but you did invent it.

Now, are you going to use that color to paint the fence?

That’s how you sound when you say Russia used Novichok to poison people.