What is the initial sign of decomposition observed in a deceased body?

The initial sign of decomposition in a deceased body is green discoloration. This change is typically associated with the breakdown of hemoglobin in the blood, which occurs shortly after death. When red blood cells break down, they release a pigment called biliverdin, which can lead to a greenish hue in the skin, especially in areas where blood pools, such as the abdomen. This discoloration is generally visible within 24 to 72 hours post-mortem, depending on environmental conditions such as temperature and humidity.

In contrast, rigor mortis involves the stiffening of the muscles after death due to biochemical processes, and it typically appears several hours after death. Body stiffness, which is essentially another way to describe rigor mortis, occurs later in the decomposition timeline. Blood pooling, or livor mortis, refers to the settling of blood due to gravity, which happens before the body shows significant signs of decomposition and typically develops within a few hours after death. Thus, it is the green discoloration that serves as the earliest external marker of the decomposing process.