In your petition, clearly explain why you are being held illegally. No. PETITION FOR WRIT OF HABEAS CORPUS AD TESTIFICANDUM.Federal habeas corpus petitions are filed in the federal district where the prisoner is incarcerated or from which he or she was sentenced. State concisely every ground on which you claim that you are being held unlawfully. Summarize briefly the facts supporting each ground. This petition, called a writ of Habeas Corpus, is filed in Federal Court (US District Court ) whether you are serving time in a federal or state prison. All Illinois Courts must accept these forms. Completing the Habeas Corpus Petition. Complete the habeas corpus petition according to the directions on the form which is enclosed in this packet.