CIS Adjudicator's Field Manual:

Foreign Language Documents and Translations.

11.3 Foreign Language Documents and Translations.

(a) Document Translations . All documents submitted in support of an application or petition must include complete translation into English. In addition, there must be a certification from the translator indicating that the translation is complete and accurate and attesting to his or her competence as a translator. See 8 CFR 103.2(b)(3) .

NOTE: Sometimes the keeper of a record will issue an “extract” version of the document. This often happens in countries where the complete document is lengthy and filled with extraneous information. Such official extracts are acceptable, but only if they contain all the information necessary to make a decision on a case. For example, an official extract of a birth certificate which fully identifies the child’s parents may be used in support of a visa petition; one which only lists the child’s name and date and place of birth may not. Furthermore, only extracts prepared by an authorized official (the “keeper of record”) are acceptable. A summary of a document prepared by a translator is unacceptable.

From time to time, you may have need to translate a document which is relevant to a case but not submitted as part of the supporting documents. In other instances, you may have reason to suspect the accuracy of a translation which has been submitted. Some offices have access to translation services provided by employees or others. In addition, USCIS officers may request translation services for documents in all major languages from the New York District Office. [(b)(2) or (b)(7)(E)]

(b) Interpreters . If a statement is taken in a foreign language, using an interpreter, and transcribed into English, it may be necessary to produce the interpreter at a subsequent hearing. Thus, when it is known or believed that the statement will be attacked on the ground that it was not correctly interpreted, it is a good practice to have the interpreter available to testify not only as to knowledge of the language but also that the statement was correctly interpreted when it was made. If the interpreter is not a regular USCIS or DHS employee, the statement should show certification that the individual was a qualified interpreter and interpreted to the best of his or her ability. Furthermore, before anyone who is not a regular USCIS or DHS interpreter can be used in such capacity, he or she must first be sworn to give full, accurate and compete translation.