Professional judgment on assessment occurs when decisions must be made. It is especially useful when external controlling measures with regards to wrong decisions have been either inappropriate or lacking. It is intended to uphold assessment quality in three categories of professional action: logical, psychological and moral. Mostly when evaluation is used for certification, professional judgment is subject to numerous tensions between external control procedures which tend to structure this judgment and factors of internal control which make the best use of the professional’s critical reflexivity. The development of new synergies appears as an essential condition to overcome such tensions. One such synergy would consist in applying research valid criteria, whether they are associated with quantitative or qualitative data, to the assessment of evaluation judgment credibility.