But in 1970 Congress created "use immunity," leaving prosecutors free to use evidence obtained independently of the immunized testimony.

If Ms. Lewinsky refused to testify after being granted use immunity, she could be held in contempt and sent to prison.

"And maybe the prosecutor can get more details than with someone who is under use immunity."

That last point is crucial in understanding the difference between transactional immunity and the more common use immunity.

But prosecutors can and do use other avenues to gather evidence against witnesses who have use immunity.

The players competed for a one-time use individual immunity (one per tribe).

The use immunity, however, must extend not only to the testimony made by the witness, but also to all evidence derived therefrom.

But these defense lawyers said that prosecutors were now taking a different approach, offering so-called use immunity.

Under use immunity, the Government agrees not to use against a witness information that he or she provides while being questioned.

Thus, there is no personal use exemption, nor any fair use immunity for home taping.