Importance of segmental hair analysis in a suspected case of attempted homicide by flocoumafen and difenacoum

The 4-hydroxycoumarin derivatives are the most used rodenticides and act as classical anticoagulants, interfering with the production of clotting factors in liver by antagonizing the action of vitamin K reductase, thereby inhibiting recycling of vitamin K1, involved in activation of blood clotting factors, resulting in massive bleeding. In this paper, we present the case of a 72-year old man providing abnormal coagulation parameters (PT-INR between 16.1 and 19.1) after hospitalization. Blood samples tested positive for flocoumafen and difenacoum, two superwarfarin rodenticides. Patient's hair specimens, sampled 19 days after his hospitalization, showed that traces of both difenacoum and flocoumafen were detected in the first 1 cm; in the intermediate segments (1–2 and 2–3 cm), both difenacoum and flocoumafen were absent, while in the distal segment (3–4.5 cm), only difenacoum was found, but in significant amounts (140 pg/mg). Exposure to difenacoum in the past months, at least 4–5 before hospitalization, was confirmed by the presence of the rodenticide in the distal segment. Moreover, among the seized material, two specimens resulted compatible with the two rodenticides.