This visa's origins began in 2000 as part of the Violence Against Women Act, and currently 10,000 U visas are granted each year. Qualifying crimes include domestic violence, felonious assault, and other felonies and serious crimes. Certification is required from the police, prosecutor, or other certifying official that the individual has been helpful.
The U visa can truly be an unexpected blessing and result of terrible circumstances for individuals seeking immigration status who normally have too many hurdles to obtain legal status. With the U visa, a number of common deportable offenses such as unlawful entry into the US, attempted unlawful entry, using false documents, etc. can be "waived" or essentially forgiven. If approved, the U visa applicant can receive legal status and work authorization for 4 years, and after 3 years can in fact apply for permanent residence. Not only that, but derivative family members (including spouses) can also receive the same benefit and potentially permanent residence.
The U Visa is truly a small slice of humanity in the current immigration system. If you were the victim of a serious crime and believe that you may qualify for a U Visa, please feel free to contact me to see if the U Visa is available for you and your family. Good luck!