Laura Langley, 38, was alleged to have killed her seven-week-old daughter Edith who collapsed at the family home in Blackpool, Lancashire, in the early hours of 20 November 2020. The Judge found that the expert evidence in the case of Professor G, of Professor N and of Professor D each at times fell below the high standard expected of expert witnesses giving evidence before the family court in this jurisdiction. This judgment illustrates a number of important lessons for expert witnesses. The criticisms go well beyond a disagreement between experts—they concern the duties of an expert to the court. An expert who appears to defend a predetermined hypothesis rather than follow the evidence risks losing credibility entirely, regardless of their qualifications or experience. This judgment illustrates that methodological rigour, transparency, and impartiality are essential to persuasive expert testimony.