At The National Association of Social Workers (NASW) website, Carolyn I. Polowy, JD and law clerk Joel Gilbertson, write on Social Workers as Expert Witnesses:
Courts of law rely upon information offered in evidence as the basis for decisions rendered. Evidence comes in many forms, including photographs, recordings, devices, forensic evidence, documents, and individual testimony. Oral testimony by witnesses is, however, often the major source of evidence at a trial.
Witnesses who testify as experts play an important role in interpreting data, explaining complex material, and drawing knowledgeable inferences based upon their training and experience. Social workers are called to testify as expert witnesses on a variety of subjects. This Law Note discusses the role of the expert witness and reviews case law confirming the role of social workers as expert witnesses in a variety of settings.
For more, see NASW.