You can for the most part evaluate intent based on actions. There are some actions which can have multiple possible intents behind them, where things get trickier. But in most situations, there is one primary consequence of something, and the action needs to be taken with deliberation, hence you can state with high certainty what the intention was, based purely on what was done. Consversely, if a person has complete freedom to complete some action, but chooses not to, then we can say their intention wasn't to do that thing.