Best site of blood sample collection in autopsy is

The hea is contracted and the chambers are empty when death has occurred from anaemia, but chambers contain blood when death occurs due to asthenia. After death, reduction of oxygen causes capillary dialtation which is followed by stasis of blood in the dilated capillaries and venules. This causes impaired venous return.As a result of which there is raised venous pressure resulting in over distension and rupture of capillaries and venules. This causes congestion and petechia haemorrhages.Haemorrhages are found in the substance of viscera. Postmoem, the blood is fluid and dark,because of increased amount of carbon dioxide. The large veins are full of blood. Hence the femoral vein is the best site of sample collection in autopsy, whereas the viscera are fully congested. Postmoem fluidity of the blood is assessed. Ref: K.S.Narayan Reddy's Synopsis of Forensic Medicine and Toxicology, 29th edition, Chapter 6, page-76,78.