Moral turpitude is a legal concept in the United States and some other countries that refers to "an act or behavior that gravely violates the sentiment or accepted standard of the community". This term appears in U.S. immigration law beginning in the 19th century.
The concept of "moral turpitude" might escape precise definition, but it has been described as an "act of baseness, vileness, or depravity in the private and social duties which a man owes to his fellowmen, or to society in general, contrary to the accepted and customary rule of right and duty between man and man."
The classification of a crime or other conduct as constituting moral turpitude has significance in several areas of law. First, prior conviction of a crime of moral turpitude (or in some jurisdictions, "moral turpitude conduct", even without a conviction) is considered to have a bearing on the honesty of a witness and might be used for purposes of the impeachment of witnesses. Second, offenses involving moral turpitude may be grounds to deny or revoke state professional licenses such as teaching credentials, licenses to practice law, or other licensed profession. Third, this concept is of great importance for immigration purposes in the United States, Canada (prior to 1976), and some other countries, since offenses which are defined as involving moral turpitude are considered bars to immigration into the U.S.
A conviction for a crime involving moral turpitude (CIMT) causes a person to be inadmissible to the United States under section 212(a)(2)(a)(i) of the INA (Immigration and Nationality Act). There are petty offense exceptions to this rule, but these exceptions do not change the meaning of the question on the Visa Waiver Program or on the visa application form, and cannot be self-certified. A controlled substance violation causes the alien to be inadmissible to the United States under section 212(a)(2)(i)(II) of the INA. They are two different sections of the law. A controlled substance violation is a CIMT. The immigration administrative proceeding does not use a controlled substance violation as a CIMT. A visa waiver program applicant admissibility is determined at the port of entry and they are subject to section 212(a) and 217 of the INA.
The second question on document I-94W for those visiting the U.S. on the Visa Waiver Program asks:
Have you ever been arrested or convicted for an offense or crime involving moral turpitude or a violation related to a controlled substance; or been arrested or convicted for two or more offenses for which the aggregate sentence to confinement was five years or more; or been controlled substance trafficker; or are you seeking entry to engage in criminal or immoral activities?