Rigor Mortis

Regarding rigor mortis, all of the following statements are correct EXCEPT:

A 32-year-old male labourer is found dead in his locked room in rural Maharashtra. The body is discovered 18 hours after death by his family. On examination, the limbs are stiff and cannot be flexed passively. The jaw is clenched, the fists are tightly closed, and the body assumes a pugilistic attitude. The ambient temperature in the room is 28°C. Which of the following statements about rigor mortis in this case is CORRECT?

A 62-year-old male is found dead in his home after 18 hours. The body shows generalized muscle stiffness affecting all limbs, neck, and jaw. The stiffness is present even in small muscles of the fingers and toes. Which feature best distinguishes this finding from heat-induced muscle contraction (cadaveric spasm) in a body exposed to fire?

A forensic pathologist is examining a body recovered from a river 36 hours after submersion. The body shows generalized rigidity, but the pathologist suspects the rigidity may be due to heat-induced muscle contraction rather than true rigor mortis. Which investigation would best differentiate between heat-induced muscle contraction and true rigor mortis?

A 52-year-old man is found dead in his apartment after 36 hours. The body shows generalized muscle stiffness and the joints cannot be flexed passively. The investigating officer suspects the time of death is approximately 24–48 hours before discovery. Which investigation is most appropriate to confirm the onset and progression of rigor mortis?