Chapter 1 - Purpose and Background
One of the general requirements for naturalization is good moral character (GMC). GMC means character which measures up to the standards of average citizens of the community in which the applicant resides.  In general, an applicant must show that he or she has been and continues to be a person of GMC during the statutory period prior to filing and up to the time of the Oath of Allegiance. 
The applicable naturalization provision under which the applicant files determines the period during which the applicant must demonstrate GMC.  The applicant’s conduct outside the GMC period may also impact whether he or she meets the GMC requirement. 
While USCIS determines whether an applicant has met the GMC requirement on a case-by-case basis, certain types of criminal conduct automatically preclude applicants from establishing GMC and may make the applicant subject to removal proceedings.  An applicant may also be found to lack GMC for other types of criminal conduct (or unlawful acts).
An officer’s assessment of whether an applicant meets the GMC requirement includes an officer’s review of:
The applicant’s record;
Statements provided in the naturalization application; and
Oral testimony provided during the interview.
There may be cases that are affected by specific jurisdictional case law. The officer should rely on local USCIS counsel in cases where there is a question about whether a particular offense rises to the level of precluding an applicant from establishing GMC. In addition, the offenses and conduct which affect the GMC determination may also render an applicant removable.
The Naturalization Act of 1790 introduced the long-standing GMC requirement for naturalization. Any conduct or act that offends the accepted moral character standards of the community in which the applicant resides should be considered without regard to whether the applicant has been arrested or convicted of an offense.
In general, an applicant for naturalization must establish GMC throughout the requisite periods of continuous residence in the United States. In prescribing specific periods during which GMC must be established, Congress generally intended to make provision for the reformation and eventual naturalization of persons who were guilty of certain past misconduct.
INA 101(f) – Good moral character definition
INA 318 – Prerequisite to naturalization, burden of proof