Definition - What does Material Witness mean?
A material witness is someone believed to have crucial information in a civil or criminal court case. Because the result may hinge on their testimony, allowances must be made to ensure their appearance in court. In some cases, the hearing or trial will be postponed until a material witness can testify.
Justipedia explains Material Witness
Someone can be classified as a material witness if they are the only person with specific information, or are one of only a few people with that information. Their knowledge about the issue at hand must be so convincing that it could determine the outcome of a criminal or civil matter.
Prosecutors often rely on material witnesses in criminal cases. As a result, federal law allows them to secure warrants for material witnesses in certain circumstances.