On January 15th, 1924, a maidservant in Beijing was murdered at the home of her employer, a bank accountant named Shen Ruihong and his wife. The case became a protracted legal battle as police, prosecutors, and the Shens’ defense lawyers argued different theories of Mrs. Shen’s involvement in the murder on the basis of divergent interpretations of fingerprints and blood stains found at the crime scene. This presentation uses this case to examine the new role that expert witnesses played in Republican China and the complex politics of professional knowledge and authority that accompanied their involvement in the legal arena.