A federal judge approved an immunity deal Friday to allow former Justice Department aide Monica Goodling to testify before Congress about the firing of eight federal prosecutors.

Goodling, who served as the department’s White House liaison, has refused to discuss the firings without a guarantee that she would not be prosecuted for her testimony. Congress agreed to the deal, Justice Department investigators reluctantly agreed not to oppose it, and U.S. District Judge Thomas Hogan gave it final approval Friday.