Many perjury cases fall under the general perjury statute set forth in 18 U.S.C. §1621. This statute describes two basic perjury situations.
In each case, to be guilty, a person must be willfully professing the truth of a material statement which that person knows is not true. In the first situation, that statement is made under oath in a situation where U.S. law allows for an oath to be administered. The second situation includes any statement or declaration in which the person making the statement asserts that the “foregoing is true and correct” “under penalty of perjury under the laws of the United States of America.”
These provisions are fairly broad and cover not only verbal statements made under oath or in a hearing, but also statements made on documents. The government must prove that the person making the statement knew it to be false and that the statement was material to the matter at hand. So, these aspects may provide grounds for a defensive strategy. In addition, the common law “two witness” rule often applies to prosecution under this statute, meaning that in many situations, there must be two sources of evidence to establish the perjury.