Example of a case law defining the term:

When the word "knowingly" is used , it means that the defendant realized what he was doing and was aware of the nature of his conduct and did not act through ignorance, mistake, or accident. Knowledge may be proved by the defendant's conduct and by all the facts and circumstances surrounding the case.[United States v. Kisting, 159 Fed. Appx. 725, 728 (7th Cir. Ill. 2005)]