SUMMARY
A continuation of an earlier article from 2002, the text explores social work's expert evidence as the meeting point between a discipline-specific technical-scientific instrument —the Social Report, which social workers alone draw up and sign— and a procedural instrument that gives it value before the courts. It recalls that this is a regulated profession with its own Code of Ethics, and traces its incorporation into the justice system from 1979 up to the 2001 Civil Procedure Act, which allows practitioners to act as court-appointed or party-appointed experts. It argues why social expertise is necessary: social workers are the professionals competent to assess and interpret social factors by investigating «on the ground», in the person's own environment. Factors are not added up: they are interrelated into a Diagnostic Interpretation. It stresses impartiality and ethics: commissioning a report means engaging a service, not «buying an opinion».