More info on expedition

http://uscis.gov/graphics/fieldoffices/texas/aboutus.htm#anchorCONTACT
A detailed explanation of the situation should be provided in a one-page support letter along with any documentation needed to support the expedite request.
AILA members must process their requests through one of the AILA Liaison Co Chairs.

Cases that are not clearly approvable will not be expedited. Requests to expedite petitions or applications that are incomplete will not be granted. All supporting documents not in English must include a certified translation. See “Documents Not in English" on our National Service Center page. There is no appeal of the denial of an expedite request.
http://uscis.gov/graphics/fieldoffices/expedited.htm
USCIS Expedite Criteria

All expedite requests are reviewed on a case-by-case basis, and are granted at the discretion of the Service Center Director. The criteria are as follows:

Severe financial loss to company or individual.

Extreme emergent situation.

Humanitarian situation.

Nonprofit status of requesting organization in furtherance of the cultural and social interests of the United States.

Department of Defense or National Interest Situation (Note: Request must come from official United States Government entity and state that delay will be detrimental to our Government.)
USCIS error.

Compelling interest of USCIS.
If a response to the expedite request is not received within 72 hours, the request is denied. The application or petition will then undergo normal processing.