Definition of Testimony
Testimony is evidence provided by a witness during a trial. A testimony can be either oral or written (through a deposition or an affidavit) and is evidence to support a fact or statement. If a witness has been called to provide testimony they have the right to remain silent and not incriminate themselves.
This right is found in the Fifth Amendment of the U.S. Constitution. This Constitutional right includes a defendant's right in a criminal trial to: (1) remain silent, (2) not be called as a witness for the prosecution, and (3) not have the fact that he exercised his right against self-incrimination used against him.
In civil cases parties or witnesses can be called to testify and they may not "enjoy an unfettered right to refuse to answer questions on Fifth Amendment grounds." The jury may also infer that the witness is guilty if they refuse to answer questions. The good news is if you are called as a witness to provide testimony in a trial your attorney will generally prepare for questions in advance of the trial.