Pain relief in hip fracture patients may be sought by injecting local anesthetic such as ropivacaine, bupivacaine, and lidocaine to the femoral area. As femoral veins are a routine sampling site for postmortem blood, this short report aimed to describe the levels of local anesthetics in ipsilateral (i.e., side of surgery) and contralateral (i.e., opposite side) femoral blood in ten medico-legal autopsy cases that had undergone a hip fracture surgery within 7 days before death. Postmortem blood samples were systematically collected from the ipsilateral and contralateral femoral veins, and toxicological analysis was performed in an accredited laboratory. The sample comprised six female and four male decedents who died at the age of 71–96 years. Median postoperative survival was 0 days and median postmortem interval 11 days. Strikingly, ropivacaine concentration was a median of 24.0 (range 1.4–28.4) times higher on the ipsilateral than contralateral side. The median ipsilateral concentration of ropivacaine clearly exceeded the 97.5th reference percentile measured in this laboratory for ropivacaine in postmortem cases representing all causes of death. The remaining drugs did not show high concentrations or notable differences between the sides. Our data clearly advise against performing postmortem toxicology on femoral blood from the operated side; the contralateral side may constitute a better sampling site. Toxicology reports that are based on blood collected from the operated area should be interpreted with caution. Larger studies are needed to confirm the findings, with accurate records of the dosage and administration route of local anesthetics.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00414-023-03000-6.