I was once called as a witness in front of a GJ. A few weeks prior the federal prosecutor showed up at my work place and interviewed me.First she offered my immunity if I cooperated, answered all of her questions and agreed to testify. I answered all of her questions truthfully that day. The GJ was far away from where I lived at the time, so I caught a ride with two others who were called to testify the same day. (we all had worked together at one point. The investigation was directed at my ex-employer) I had nothing to hide and fervently believed my ex-employer had done nothing illegal. The day of the proceedings she asked mostly the same questions I had already answered, except for one. That question was about my tax filings. It was a little cash job and I was young and dumb, it never even occurred to me to file taxes for it. She phrased the question with, "sitting beside me is Mr X from the IRS and he has agreed not to prosecute you as you are cooperating". I was floored.
The other two I drove there with, one took the 5th on the very first question (she had told us on the drive that was her intent, she didn't do anything illegal either, she was a little "backward", too) They then asked her if she intended to answer the same way to all of their questions, she answered affirmatively, then she was dismissed. The second person had intended to answer all of their questions, like me, he didn't believe he nor my ex-employer had broken any laws. He answered a bunch of questions and then they asked about his old gambling debt/winnings. He stopped there and said he was taking the 5th. He and the prosecutor were then called into the judges chambers to discuss the matter. He told the judge, when he spoke with the FP prior, he told them he would answer anything they liked about the employer as long as they didn't drag his past into it. The judge ruled, if that was what was agreed upon then so be it. He went back on the stand and finished answering all of their questions relating to the employer.
In the end, no charged were brought against my employer.
