DHS Special Events Program and Support Act This bill provides statutory authority for the Department of Homeland Security (DHS) to conduct security assessments and provide security and situational awareness support for pre-planned special events that are not designated as National Special Security Events. (National Special Security Events are major federal government or public events so designated by the President or DHS, such as presidential inaugurations, major international summits, and major sporting events.) Under the bill, DHS must establish a standard process for federal, state, local, tribal, and territorial officials to voluntarily submit requests to DHS for event assessment and possible security and situational awareness support. DHS must assess such requests using a risk-based methodology and include a process for expedited consideration and, where appropriate, for reassessment. DHS must also carry out research and development of technologies and techniques for enhancing DHS's security and situational awareness support to such officials relating to mass gatherings in a manner consistent with constitutional, privacy, civil rights, and civil liberties protections.