Confirming that a person holds a Ph.D. is a fairly simple matter, so long as you know which school awarded the degree. Although some information is protected by the Family Educational Rights and Privacy Act, known as FERPA, degrees are considered "directory information" that may be shared with anyone who requests confirmation. Even after the school confirms that an individual received a Ph.D., it may also be worth looking into the university itself, to determine if it is regionally accredited or a so-called "diploma mill" whose degrees are of little value.
Contact the university listed as the school that conferred the degree, either through the Office of the Registrar or the Office of Student Records. Provide the full name of the student and ask for his degree history. If you do not know the degree-granting school, ask the person directly: If the individual represents himself as a degree-holder, he should have no problem indicating where he received it. If you do not have direct contact with the individual, try an Internet search of the person's name, including the term "Ph.D." Most people holding that high academic rank have some presence on the Internet, and you should be able to determine the name of the issuing school.
Determine the accreditation status of the degree-granting school. The U.S. Department of Education maintains a database of all postsecondary educational institutions and their accrediting bodies; simply enter the name of the school and you can determine if it is recognized by any independent accrediting agency.
Request formal transcripts from the applicant to learn more details about the Ph.D., including courses taken, dissertation and grades. This information is protected by FERPA, and can only be requested by the student.
Do not be misled by fancy diplomas, as these can easily be falsified or produced by schools without accreditation.