Blood clots forming in the legs and migrating to the heart or lungs can certainly cause sudden death. Physicians maintain a high index of concern for this kind of problem with patients that are immobilized for hospitalization, surgery, as well as other medical reasons.
The three classically discussed factors leading to blood clot formation are stasis (immobilization), blood vessel wall damage, and medical conditions causing an increased tendency of clotting. These three factors are classically referred to as Virchow’s Triangle.
There is a genetic abnormality (Leiden factor V) observed in higher prevalence in today’s Galilean Jews, which carries an increased risk for blood clot formation. It has been suggested that Jesus may have had this condition, which along with immobilization on the cross, lead to the formation of a blood clot which then migrated to his heart or lungs causing sudden death. This has been offered as an explanation of Jesus’ rapid death on the cross, namely within six hours. Crucifixion often lasted much longer, even several days before the victim finally died.
While such an occurrence is not impossible, Jewish migration over the past 2,000 years does not allow direct comparison of population genetic profiles from Jesus’ time to that of today. Additionally, crucifixion victims were not immobilized but would have been writhing on the cross to facilitate respiration and attempt to relieve pain. So, the stasis factor of Virchow’s Triangle was not present. Also, Jesus’ brief time on the cross seems inadequate to allow for clot formation.