Question

The time a murder victims deatg is commonly estimated by the flexibility/stiffness of the body. Explain why this is possible. What other information would be beneficial?

Answer 1

Rigor mortis or cadaveric rigidity, initiates in the body 1-2 hours after death. It takes around 12 hours for Rigor mortis to complete development. Rigor mortis will remain in the developed state for another 12 hours. Only after this 12 hr period is over, will it disappear in the next 12 hours. Thus, the time of death can be predicted.

Rigor mortis start typically in the eyelid muscles by 1-6 hrs (around 2-4 hrs) of death. It then affects the lower jaw muscles and muscles of trunk, upper and lower extremities. The muscles of fingers and toes are affected last. This same sequence also applies to disappearance of Rigor mortis.

When a person dies, there will be no ATP generated. ATP is required for muscle contraction. When the supply of ATP to the muscle stops, the muscle will be stiffened as the myosin cannot detach due to lack of ATP. Hence, the muscle will remain in a contracted state permanently. It takes some time for rigor mortis to set in as anaerobic respiration will provide some ATP to the muscle for contraction and relaxation.

The table indicates estimation of time of death by examining the body.

Body condition                                                                                 Time since death

Body is warm with no rigor mortis                                            Death is within 3 hours

Body is warm and stiff                                                                  Death occurred between 3-9 hours possibly

Body is cold and stiff                                                                       Death occurred 9-36 hours prior                               

Cold and no stiffness                                                                     The person died 36 or more hours previously

Other parameters checked are:

1) Drying of blood/ Pallor mortis: Blood contains cells and water. Hence, after death, due to reduction in water content, the blood will start drying off. Circulation ceases by 15-30 min after death. Thus, the body starts becoming pale.

2) Algor mortis: Human body will start cooling after death as they can no longer control their body temperature.

2) Livor mortis: Due to the heart stopping its function, the blood depends on gravity and will start collecting in different parts of the body. Hence, depending on how the body is placed, the parts of the body that have pooled blood will differ. Blood collects at base if the body is lying down.

Biochemical studies of C.S.F., Vitreous Humor, Aqueous humor can also be used to determine death. Parameters include discoloration stains on body, whether the body is putrefied or there is saponification of body fat, as well as maceration. Maceration cause softening of tissue due to collection of water. The physical condition of person may also be beneficial to know as they can affect rigor mortis. Rigor mortis occurs faster if the person has fever. Antibiotics may affect the time of bacterial mediated putrefaction. Contents of the stomach indicate how early food was ingested and how much digestion has occurred.