What does Perjury mean?
Perjury is the criminal act of giving false information to government officials or in testimony. Perjury occurs if an individual provides false information on certain types of official documents or if they are under oath. Perjury specifically occurs if the false statements are "of great importance that seriously threaten the integrity of governmental processes and that indicate a disposition on the part of the speaker to subvert governmental action." False statements which are simply careless or lack precise information may not be considered perjury if they are not material in nature. Proving materiality can be very difficult and courts have held that some statements, even though they are clearly lies, were not considered perjury because they were innocent and not material to the case.
In criminal trials the act of perjury is very serious because the judicial system in the United States is predicated on the assumption that testimony presented to the court is accurate and reliable. Witnesses do, however, have the right to plead the fifth and refuse to testify if they believe such testimony could be self-incriminating. This right is outlined in the U.S. Constitution under the Fifth Amendment.