What is the earliest definite site of external putrefaction?

Ans: (c) Right iliac fossaRef: NG Rao, Textbook of Forensic Medicine and Toxicology, 2nd edition, Page 150Greenish or bluish green discoloration is a sign of decomposition.This discolouration is due to formation of sulphamethemoglobin from H2S and hemoglobin.Sites of occurrenceInternally, it is first seen as Reddish brown discolouration on inner surface of vessels especially aorta (earliest sign). It is also seen on undersurface of liver where it is in contact with transverse colon (along with external discolouration).Externally it is seen as greenish discolouration in the Right iliac fossa in skin over the caecum (as contents of bowel here are more fluid and full of bacteria).Timeline since deathAppears in 12 to 18 hours in summer and 1 or 2 days in winter.Passage of bacteria through blood vessels results in formation of sulphamethemoglobin along route causing greenish or reddish brown liner branching pattern on skin (marbling) first on shoulder, roots of limbs, thighs, side of abdomen, chest and neck - prominent in 36 to 48 hours.