Secret Service Protective Privilege Act of 1999 - Amends the Federal criminal code to prohibit testimony by Secret Service personnel or former personnel regarding information affecting a protectee (defined as the President, Vice President, and specified other officials) that was acquired during the performance of a protective function in physical proximity to the protectee from being received in evidence or otherwise disclosed in any proceeding in or before any court, grand jury, department, officer, agency, regulatory body, or other authority of the United States, a State, or a political subdivision thereof.

Makes exceptions: (1) with respect to information that, at the time it was acquired by Secret Service personnel, was sufficient to provide reasonable grounds to believe that a crime had been, was being, or would be committed; or (2) if the privilege is waived by the protectee or the legal representative of a protectee or deceased protectee.

Specifies that the proximity of Secret Service personnel to a protectee engaged in a privileged communication with another shall not, by itself, defeat an otherwise valid claim of privilege.