From an old 1911 Encyclopedia
Affidavit (Med. Lat. for he has declared upon oath, from affidare, fides, faith), a written statement sworn or affirmed to before some person who has authority to administer an oath or affirmation. Evidence is chiefly taken by means of affidavits in the Chancery Division of the High Court of Justice in England on a petition, summons or motion. Interlocutory proceedings before trial are conducted by affidavits, e.g. for discovery of documents, hence called affidavit of documents. Affidavits are sometimes necessary as certificates that certain formalities have been duly and legally performed (such as service of proceedings, &c.). They are extensively used in bankruptcy practice, in the administration of the revenue and in the inferior and county courts. In testamentary causes, all documents of any kind, such as wills, codicils, drafts or instructions of same must be filed in the form of affidavits (termed affidavits of scripts.) In Scotland the testimony of witnesses by affidavit is almost unknown, except in a few non-contentious cases as prima facie evidence. In the rules of the Supreme Court (R.S.C. Ord. Xxxviii.) certain formal requirements are laid down for all affidavits and affirmations in causes or matters depending in the High Court. An affidavit must consist of title, body or statement and jurat. It must be written or printed on foolscap, bookwise, in the first person; give correctly the names of the parties to the action; and the description and true place of abode of the deponent. An affidavit is confined, except on interlocutory motions, to such facts as the witness is able of his own knowledge to prove. The signature of the deponent must be written opposite to the jurat, which must contain the place, date and time of swearing, and this signed by the officer or magistrate before whom the affidavit is sworn. An affidavit sworn on a Sunday is not invalid. Quakers, Moravians and Separatists were first privileged to make a solemn declaration or affirmation, and by the Common Law Procedure Act 1852 and other statutes all persons prevented by religious belief from taking an oath were allowed to affirm; and, finally, by the Oaths Act 1888, every person who objects to be sworn is allowed to affirm in all places and for all purposes where an oath is required by law. By an act of 1835 justices are permitted to take affidavits in any matter by declaration, and a person making a false affidavit in this way is liable to punishment. The same act prohibited justices of peace from administering oaths in any matter in which they had not jurisdiction as judges, except when an oath was specially authorized by statute, as in the bankruptcy law, and excepting criminal inquiries, parliamentary proceedings and instances where oaths are required to give validity to documents abroad. Scottish justices can act in England and vice versa. The Oaths Act 1888 and the Commissioner of Oaths Act 1889 consolidated all previous enactments relating to oaths and gave the lord chancellor power to appoint commissioners for oaths to take affidavits for all purposes (see Oath.) Under the Debtors Act 1869 a plaintiff may file an affidavit for the arrest of a debtor (affidavit to hold to bail) when the debt amounts to L. 50 or upwards, where it can be shown that the debtor's absence from the kingdom would materially prejudice the prosecution of the action.
Affidavits may be made abroad before any British ambassador, envoy, minister, charge d'affaires, secretary of embassy or legation, consul or consular agent.
In the United States affidavit has the same meaning as in England and its general uses are the same, but it is not substituted for oral evidence in court to anything like the extent to which that is done in the English courts of chancery. The statutes of each state designate the persons before whom affidavits may be made outside the state, and special commissioners are appointed for that purpose by each state. Affidavits made abroad must be made before such commissioners or persons so designated, who are usually diplomatic and consular officials, justices, notaries public or mayors. Affidavit of documents is not generally used in the United States; discovery is procured by motion.