The easiest way for prosecutors to scuttle a criminal case is to immunize those people who are at the greatest risk of criminal indictment. Often prosecutors will avoid immunity deals in favor of offering plea bargains to key players, tying their cooperation against others to reduced sentences. Although a witness can lose an immunity deal by withholding evidence or lying, a witness can undermine cases against superiors by tailoring their accounts or memories to avoid statements showing intent or knowledge.

Combetta's immunity deal was perplexing. Combetta used a product called BleachBit to eradicate evidence of Clinton emails after a telephone conference with Clinton staffers. When he used the product, he admitted that he knew that Congress had issued a subpoena ordering the preservation of the evidence. Then, this month, it was alleged by a "Twitter sleuth" that Combetta, acting under the alias "stonetear," solicited advice on how to change email records to remove a "VIP's (VERY VIP) email address."  Either Combetta did not disclose this effort in violation of his immunity deal or the Justice Department effectively removed a serious threat of indictment though the agreement. Despite immunity deals pledging cooperation with all parts of the government, both Pagliano and Combetta have refused to answer questions from Congress, and Pagliano is facing a contempt sanction.