The congressman insisted the witnesses against him were lying under government pressure or immunity agreements.

A special immunity agreement was negotiated with the British to allow the scientists to work unharmed.

Administration officials note that more than 100 immunity agreements have been signed.

Niger, for example, has determined that its Constitution does not allow it to grant the immunity agreement.

Under her immunity agreement she cannot talk to the press without his permission.

He testified against his sister and her husband in court in 1951 as part of an immunity agreement.

In those cases, however, the immunity agreements are accords negotiated by both sides.

Because to do otherwise would have violated her immunity agreement, she explains, and "I needed to take care of myself and my family."

But prosecutors wanted another day to talk with her lawyer about whether the immunity agreement should be renegotiated, he said.

After all, that's the purpose of the immunity agreement.