The Role of the Expert Witness and the Abuse of Differential Diagnoses in Court

The suspicion that a child sustained injuries in non-accidental circumstances does not only have a medical and social but also a potentially legal impact. This sets it apart from all other medical paediatric signs, symptoms, and physical findings in need of a proper differential diagnosis. Probably the most important difference is that when these cases go to court the suspicion can, and in most cases will, be debated by forensic medical experts/expert witnesses who act for the court, the public prosecutor, or for the defence. It is the duty of an expert witness to explain the reasons for the suspicion and to explain the differential diagnoses of the physical findings to laypersons (e.g., child protection and the police) or to the participants in court procedures (judge, public prosecutor, and defence lawyer). The explanation has to be done in understandable lay language and in a neutral and preferably evidence-based way. In this chapter the duties and responsibilities of an expert-witness will be discussed. Also examples will be given of the abuse in court of existing diseases, like e.g. vitamin D deficiency and Ehlers-Danlos, or even the introduction in court procedures of non-existing diseases like temporary brittle bone disease.