You cannot be convicted for a crime you did not commit, at least not without it being a wrongful conviction — which, unfortunately, does happen. But just refusing to actually commit the crime does not always mean you’re going to avoid all charges. In conspiracy cases, you can be arrested simply for planning something, even if you never carry it out.
Taking action of some sort is generally part of a conspiracy charge, but that does not mean the action in and of itself was illegal. It was just a step in the process.
For instance, imagine that you and a friend are planning to move a large supply of illegal drugs to another location, where it can be distributed within that market. This is drug trafficking, and it is illegal. You talk about it in person and then through text messages, and you determine that the easiest way to move the product is with a U-Haul van. You go to the nearest center and rent the van.
At this point, the police break the whole thing wide open. Someone tipped them off after seeing the messages on your friend’s phone. They arrest both of you before you can even pick up the shipment.
It’s natural for you to argue that you can’t be charged with drug trafficking because, quite simply, you never engaged in drug trafficking. No illegal substances were moved under your control. And that is true. But it does not mean you can’t be charged with a conspiracy to carry out that same act. You planned to do it and took action toward doing it — even though it is not illegal to rent a van — before the police arrived.
It’s important to know how charges like this are related and how they differ. Your situation is going to determine your best legal defense options, and you also need to understand exactly what they are and what steps to take.