The problem arises years later, when a Green Card holder wants to become an American citizen and tries to complete the Application for Naturalization (Form N-400).
This is a very long form, with hundreds of questions requiring many details and complete accuracy in responses. The Green Card holder realizes - sometimes - that he or she does not remember what information was provided in answer to the same questions on the previous applications or petitions.
This lapse of memory could be a problem, because at the time of the citizenship interview the Immigration Officer will have all the previous files on his desk and will compare all the information that was ever given to the U.S. Citizenship and Immigration Services (CIS) about this applicant for citizenship. A discrepancy, or a contradiction, may cause the CIS to accuse the applicant of lying - either on the present citizenship application (Form N-400) or on the previous immigration forms. This may lead to a denial of the Application for Citizenship, or even to a Notice To Appear (NTA) in Immigration Court for a deportation hearing. (To read more about the Immigration Court - click here).
If many years have passed since the time of your immigration or adjustment of status, and if you do not remember all the details, be candid with your immigration lawyer about what you don't remember. You and your immigration lawyer should delay filing your Application for Naturalization (Form N-400) until your immigration lawyer obtains a complete copy of your file from the CIS (and a copy of your file from the Immigration Court, if there was one), and until a decision can be made how to respond truthfully and accurately to various questions. It is even possible, sometimes, that an experienced immigration lawyer would advise you not to apply for American citizenship, just to remain a Green Card holder.