Chapter 1: Purpose and Background
USCIS conducts an investigation and examination of all naturalization applicants to determine whether an applicant meets all pertinent eligibility requirements to become a U.S. citizen. The investigation and examination process encompasses all factors relating to the applicant's eligibility:  See INA 335. See 8 CFR 335.1 and 8 CFR 335.2.
Completion of security and criminal background checks;
Review of the applicant’s complete immigration record;
In-person interview(s) with oral and written testimony;
Testing for English and civics requirements; and
Qualification for a disability exception.
USCIS officers have authority to conduct the investigation and examination.  See INA 335(b). See 8 CFR 332.1 and 8 CFR 335.2. The authority is delegated by the Secretary of the Department of Homeland Security. The authority includes the legal authority for certain officers to administer the Oath of Allegiance, obtain oral and written testimony during an in-person interview, subpoena witnesses, and request evidence.  See INA 332, INA 335, and INA 337. See 8 CFR 332, 8 CFR 335, and 8 CFR 337.
The applicant has the burden of establishing eligibility by a preponderance of the evidence throughout the examination.  See 8 CFR 316.2(b). The officer must resolve any pending issues and obtain all of the necessary information and evidence to make a decision on the application. Uniformity in decision-making and application processing is vital to the integrity of the naturalization process. Consistency in the decision-making process enhances USCIS’s goal to ensure that the relevant laws and regulations are applied accurately to each case.
Beginning in 1906, a complete examination and questioning under oath was required of the “petitioner” (now “applicant”) for naturalization and his or her witnesses at the final hearing for naturalization in court.  In 1981 Congress enacted legislation which eliminated the character witness requirements of naturalization, though USCIS has the authority to subpoena witnesses if necessary. Congress amended the statute in 1940 to include English language requirements and a provision for questioning applicants on their understanding of the principles of the Constitution.  See the Nationality Act of 1940, Pub. L. 76-853, 54 Stat. 1137.
Today, USCIS conducts an investigation and examination of all applicants for naturalization to determine their eligibility for naturalization, including the applicant’s lawful admission for permanent residence, ability to establish good moral character, attachment to the Constitution, residence and physical presence in the United States, and the English and civics requirements for naturalization.
C. Legal Authorities