Almost all crimes have a mental state requirement, meaning that the prosecution must prove that the defendant acted with a particular state of mind. In that vein, some crimes require that the defendant act “willfully.” But what it means to act willfully can vary.
Under many circumstances, “willfulness” describes a situation in which the defendant acted purposely. In other words, it simply means that the prosecution must prove that the defendant meant to commit the act in question, regardless of whether he intended the result or knew he was breaking the law.
For example, assume John brings down a buck while deer hunting. A state trooper finds and stops him. It turns out that, although John didn’t realize it, he was hunting on private property and thereby broke the law. John purposely hunted on someone else’s property without permission. He knew he was hunting, even though he didn’t know it was someone else’s property. Depending on the law, his knowledge may be enough to meet the willfulness requirement. (But, if the law requires that the defendant know that he is on private property, John isn’t guilty.)
“Willfulness” can also indicate a requirement that the defendant either intend a particular result or knowingly break the law.
If charged with a crime using this variation on willfulness, John could be guilty if the prosecution shows that he actually knew that he was hunting on another’s private land. Or, the prosecution might have to additionally show that he knew it was illegal to hunt on private land.
For more, see General Intent Crimes vs. Specific Intent Crimes.
“Willfulness” can have yet another meaning, one that covers a defendant’s intentional effort to avoid confirmation that he is breaking the law. (For a detailed discussion of this concept, see Willful Blindness and Criminal Liability.)
Returning to the hunting example, suppose John knew there was a possibility that he was hunting on private property. As he entered the property, he saw a far-away sign that he couldn’t read. He didn’t know what the sign said, but, because he was afraid it said, “Private Property—No Trespassing,” he walked past it without looking at it more closely. The law prosecutors charge him with requires that the defendant hunt on private property without permission, with knowledge that the property is private. Given the facts, they may well be able to get a conviction on the grounds that John’s willful blindness satisfies the state-of-mind requirement.