A "crime of moral turpitude" (CMT) is basically one that was done recklessly or with evil intent, and which shocks the public conscience as inherently base, vile, or depraved, contrary to the rules of morality and the duties owed between people or to society in general.
That's not exactly a bright-line or easy definition, unfortunately. And the CMT definition is one of the most important for non-citizens or immigrants to understand, especially if they've had run-ins with law enforcement.
Having a conviction for a crime of moral turpitude on one's record—or in some cases, even just admitting to the crime—can block one's application for a visa or green card, as described in Crimes That Make U.S. Visa or Green Card Applicants Inadmissible. (See I.N.A. § 212(a)(2)(A)(i)(I).) It can also cause someone who already has a U.S. visa or green card to be removed from the U.S., as described in Crimes That Will Make an Immigrant Deportable. (See I.N.A. § 237(a)(2)(A)(i).)
What's more, it can block a green card holder from showing the "good moral character" necessary for a successful application for U.S. citizenship.
Making the analysis even harder, no one is ever charged with something called a "crime of moral turpitude." It's a catch-all (or catch-a-lot) description, which can apply to almost any type of crime if and when appropriate. Some advocates argue that it's unconstitutionally vague, but this argument has so far gone nowhere.
A crime can be a CMT regardless of how seriously the criminal justice system views it (whether it's a misdemeanor or felony) and regardless of the sentence imposed for it.
Given its importance, you would think that the term "crime of moral turpitude" would actually be defined within the immigration law, or that a list of specific crimes would be included there. However, the lawmakers left this to the relevant agencies—and ultimately the U.S. courts—to deal with.
The definition alluded to above comes mostly from written opinions by the Board of Immigration Appeals (B.I.A.). It has described moral turpitude as a "nebulous concept," and one that "refers generally to conduct that shocks the public conscience as being inherently base, vile, or depraved, contrary to the rules of morality and the duties owed between man and man, either one's fellow man or society in general." It has also said that the person committing it should have had either an "evil intent" or been acting recklessly.
Courts have also called CMTs "per se morally reprehensible and intrinsically wrong."
This collection of words seems to point to a highly subjective determination. In other words, if the immigration official or judge thinks the crime sounds morally wrong, or perhaps mean and nasty, it's probably a crime of moral turpitude.
Among the many specific offenses that the U.S. government and courts have determined to be CMTs in individual immigrants' cases are:
However, the above list contains only brief summaries of various types of crimes. Most criminal convictions are based on state law, so their actual definitions will be lengthier and more complex. The details within the language of the statute might potentially affect the determination of whether or not a particular crime is a CMT.
This is not an area for self help. The law on crimes of moral turpitude is constantly developing, and only a lawyer familiar with local criminal laws as well as the immigration code can provide a full analysis of your case.