The "U" Visa was created by Congress in 2000 through
the Victims of Trafficking and Violence Protection Act
of 2000. It is a visa for those that have been victims of
crimes (and typically violent ones) and are cooperating with law
enforcement officials. To be eligible, one has to, among other
things, be a victim of or a witness to a crime and suffer harm
(whether physical or mental), make a report of that crime to the
police, and cooperate with the police. If all these base criteria
are met, an authorized police official or other government official
(like a judge or prosecutor) has to sign a USCIS Form (I-918)
indicating that you were in fact a victim of or witness to a crime
and are cooperating with an investigation as well as describe how
you are cooperating. With this document and signature in hand, you
can apply for the U Visa with USCIS. Once the U Visa is approved,
you are eligible to apply for permanent residence after three years
of being in U Visa status.