Rigor mortis is typically observed how many hours after death?

Rigor mortis, which is the stiffening of muscles after death, typically sets in between three to six hours following a person's death. This process begins as the body's biochemical changes commence due to the cessation of circulation, leading to a lack of oxygen and energy and resulting in muscle stiffness.

Within this timeframe, the body undergoes several physiological changes as enzymes begin to break down the cells, and the lack of ATP (adenosine triphosphate) causes myosin and actin filaments in muscle cells to become locked together, resulting in rigidity. The process generally peaks around 12 hours after death, and rigor mortis continues for around 24 to 36 hours before the body begins to relax again as decomposition progresses.

The timeframe mentioned in the correct choice aligns well with the scientifically established understanding of rigor mortis and its development post-mortem.