http://travel.state.gov/passport/get/minors/minors_834.html
5. Present Parental Application Permission Documentation
(for minors under age 14)
1. Both parents must appear together and sign or
2. One parent appears, signs, and submits second parent's notarized statement of consent authorizing passport issuance for the child (a notarized Form DS-3053, Statement of Consent: Issuance of a Passport to a Minor Under Age 14 , or a notarized written statement with the same information on a sheet of paper from the non-appearing parent) or
3. One parents appears, signs, and submits primary evidence of sole authority to apply (such as one of the following):
Child's certified U.S. or foreign birth certificate (with translation, if necessary) listing only applying parent; or
Consular Report of Birth Abroad (Form FS-240) or Certification of Birth Abroad (Form DS-1350) listing only applying parent; or
Court order granting sole custody to the applying parent (unless child's travel is restricted by that order); or
Adoption decree (if applying parents is sole adopting parent); or
Court order specifically permitting applying parent's or guardian's travel with the child; or
Judicial declaration of incompetence of non-applying parent; or
Death certificate of non-applying parent.
If none of the above documentation is available, the applying parent/guardian should submit a Form DS-3053: Statement of Consent: Issuance of a Passport to a Minor Under Age 14 .
See site for complete details...