Glossary
Witness
A person who testifies under oath about what they observed, did, or know. Witnesses can be parties to the case or strangers to it. Their job is to provide information, not to argue for either side.
Witnesses get there one of two ways: voluntarily (a party calls them and they show up) or by subpoena (the court orders them to appear). Once on the stand, they're sworn in, asked questions by both sides, and have to answer truthfully.
A witness who lies under oath commits perjury: a serious crime. A witness who refuses to answer without a valid privilege can be held in contempt.
There are different categories: fact witnesses (testify about what they observed), expert witnesses (qualified by training or experience to give opinions on specialized issues), and character witnesses (in some cases, testify about a party's general reputation).