Many countries have a Court of Audit, a body charged with performing financial audits on the government. Or put simply a Court of Audit has to check whether public expenditure is used in a sensible way. Because of this role, this body should be independent from the government.
However, virtually all Courts of Audit are either appointed by either the executive branch or the legislature. Therefore the independence of this institution might be questioned, as its members are appointed by the people they have to monitor. Nor seems the direct election of auditors by the public a sensible option.
Since a Court of Audit is charged with reviewing government policy rather than deciding on such matters, this body seems to be suited for sortition. This means that the auditors are randomly selected from either the general public or from a pool of volunteers. In this manner the independence of the auditors will be ensured.
This Court of Audit will be supported with a professional staff of civil servants trained in financial and legal matters. Nonetheless, it will be the auditors who will decide upon what investigations are undertaken and what question are made. Also the auditors will have to authority to hear people in their inquiries.