Prosecution of a witness using evidence independent of his or her immunized testimony will require the government to meet its burden under Kastigar, supra, of proving that the evidence it intends to use is not tainted by the witness's immunized testimony. In order to ensure that the government will be able to meet this burden, prosecutors should take the following precautions in the case of a witness who may possibly be prosecuted for an offense about which the witness may be questioned during his/her compelled testimony:
- Before the witness testifies, prepare for the file a signed and dated memorandum summarizing the existing evidence against the witness and the date(s) and source(s) of such evidence;
- Ensure that the witness's immunized testimony is recorded verbatim and thereafter maintained in a secure location to which access is documented; and
- Maintain a record of the date(s) and source(s) of any evidence relating to the witness obtained after the witness has testified pursuant to the immunity order.