In law, attendant circumstances (sometimes external circumstances) are the facts surrounding an event.

In criminal law in the United States, the definition of a given offense generally includes up to three kinds of "elements": the actus reus, or guilty conduct; the mens rea, or guilty mental state; and the attendant (sometimes "external") circumstances. The reason is given in Powell v. Texas, 392 U.S. 514, 533 (1968):

...criminal penalties may be inflicted only if the accused has committed some act, has engaged in some behavior, which society has an interest in preventing.

The burden of proof is on the prosecution to prove each "element of the offense" in order for a defendant to be found guilty. The Model Penal Code §1.13(9) offers the following definition of the phrase "elements of an offense":

(i) such conduct or (ii) such attendant circumstances or (iii) such a result of conduct as

(a) is included in the description of the forbidden conduct in the definition of the offense; or

(b) establishes the required kind of culpability; or

(c) negatives an excuse or justification for such conduct; or

(d) negatives a defense under the statute of limitations; or

(e) establishes jurisdiction or venue;