The petitioner must be a U.S. citizen
By law, only U.S. citizens can request their foreign born fiancé(e)’s to enter the U.S via the K1 visa. Thus, lawful permanent residents must first naturalize in order to request their fiancé(e)s through this process. Proof of U.S. citizenship can be evidenced in the form a of a copy of a birth certificate issued in the U.S., a U.S. passport, a copy of a certificate of citizenship, or a copy of a naturalization certificate.
Both parties must have a bona fide intent to marry within 90 days of the fiancé(e)’s entry.
Both fiancé(e)’s must prove to the satisfaction of the government that they both have an intent to marry for non-immigration purposes. Evidence of this intent is commonly evidenced in a pair of notarized letters from each party. The government may request additional evidence which can include things such as wedding announcements, communications, or other indicators of intent to marry.
The U.S. citizen must provide a certified criminal record if one exists.
This requirement is set out under the Immigration and Nationality Act (INA) section 214(d)(1). Criminal records can be normally obtained from the clerk of the court in the jurisdiction where the conviction occurred. If the citizen has an arrest record, but NOT a conviction, it may be necessary to obtain a letter from either the arresting agency or the court indicating that the case was never filed or that the matter was dismissed.
If the U.S. citizen has a criminal record, other than minor traffic problems, the citizen should consult with an immigration attorney prior to filing the I-129f petition.