Mass. Gen. Laws ch. 261 § 27B
Upon or after commencing or answering to any civil, criminal or juvenile proceeding or appeal in any court, including but not limited to civil actions, proceedings for divorce or separate support, summary and supplementary processes, and proceedings upon petitions to vacate, for review or, upon appeal in a criminal case, any party may file with the clerk an affidavit of indigency and request for waiver, substitution or payment by the commonwealth of fees and costs upon a form prescribed by the chief justice of the supreme judicial court and in accordance with the standards set forth in sections twenty-seven C to twenty-seven F, inclusive, and sworn to under oath by the affiant.
An indigent party may subsequently file one or more supplementary affidavits requesting the waiver, substitution or payment by the commonwealth of fees and costs not previously granted at any time while the case is still pending in the original court or elsewhere.
Mass. Gen. Laws ch. 261, § 27B