What is the legal term for being accused of a crime that was committed prior to the date of when the act became a crime?

What is the legal term for being accused of a crime that was committed prior to the date of when the act became a crime?

I remember learning this in high school civics class, and the Latin term has been illuding me for months and it is driving me crazy. I have tried various search engines and the computer just cannot understand the question I am asking. In other words, on Monday you pick your nose, and Tuesday there is a law made to make nosepicking illegal, and Wednesday your are arrested and penalized for picking your nose on the previous Monday. I just know that I learned a Legal Latin term describing this circumstance, but I just can’t remember.

Asked on August 2, 2010 under Criminal Law, California

Answers:

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