According to the Treaty on the Non-Proliferation of Nuclear Weapons (NPT), the safeguarding of fissionable material in the peaceful nuclear industry is carried out by the International Atomic Energy Agency as follows (IAEA (1972)): The operator of a safeguarded facility reports to the IAEA, through his national or multinational authority, the data required for the closing of a material balance. IAEA inspectors verify on-site the validity of the reported data by independent measurements, usually on a random sampling basis. The inspectorate then establishes with the aid of the reported data a material balance upon which it bases its technical conclusions.

In Chapter 7 we dealt with the decision-theoretical aspects of drawing conclusions from unfalsified material accountancy data, postponing the subjects of independent verification and deliberate falsification to the present chapter. Now, in the light of our experience with the subtleties of verification theory, we have first to face a rather fundamental question. Since the possibility of deliberate data falsification on the part of a facility operator intent on concealing a diversion of nuclear material cannot be excluded, and indeed ultimately justifies the very existence of a verification system, should his a a priori suspect data be included at all in the inspector's decision process?