<prompt> In a suspected case of death due to poisoning where cadaveric rigidity is lasting longer than usual, it may be case of poisoning due toLeadArsenicMercuryCopper  <response>: Ans. is b i.e. arsenic Arsenic poisoning delays rigor mortisAlso rememberRigor is delayed by cold and accelerated by heatRigor mortisCommences in about 2-3 hrsDevelops in-12 hrsPersists for-12 hrsPasses off -12 hrsMore questions on Rigor mortisRigor mortis first appears in involuntary muscles and then in voluntary muscles.First involuntary muscles to be involved in rigor mortis - heart musclesFirst voluntary muscle to be involved in rigor mortis - Muscle of eyelid 