What made Swango particularly dangerous was the cover provided by his medical credentials — a licensed physician moving between hospitals and countries, poisoning patients in settings built on trust. Estimates of his victims reach as high as sixty, though he admitted to only four deaths, a gap that reflects both the difficulty of detecting physician-perpetrated harm and institutional failures that allowed him to continue practicing after early suspicions arose. He remains one of the most extensively investigated cases of medical serial killing in American history.