The president may also refuse either to sign or veto a bill. Investigations are conducted to gather information on the need for future legislation, to test the effectiveness of laws already passed, to inquire into the qualifications and performance of members and officials of the other branches, and, on rare occasions, to lay the groundwork for impeachment proceedings. Frequently, committees call on outside experts to assist in conducting investigative hearings and to make detailed studies of issues. There are important corollaries to the investigative power. One is the power to publicize investigations and their results.
Most committee hearings are open to the public and are widely reported in the mass media.
Congressional investigations thus represent one important tool available to lawmakers to inform the citizenry and arouse public interest in national issues. Congressional committees also have the power to compel testimony from unwilling witnesses and to cite for contempt of Congress witnesses who refuse to testify and for perjury those who give false testimony. In contrast to European parliamentary systems, the selection and behavior of U.S. legislators has little to do with central party discipline. Thus the members of Congress owe their positions to their local or state electorate, not to the national party leadership nor to their congressional colleagues. As a result, the legislative behavior of representatives and senators tends to be individualistic and idiosyncratic, reflecting the great variety of electorates represented and the freedom that comes from having built a loyal personal constituency.