The Mortis Brothers
Rigor Mortis, Algor Mortis and Livor Mortis – sometimes referred to as the “Mortis Brothers”
Rigor Mortis
Rigor Mortis is due to a biochemical change in the muscles that occurs several hours after death, though the time of its onset after death depends on the ambient temperature.
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Within ½ to 1 hour = becomes apparent
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Approx 12 hours = increases to max
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Approx 12 hours = set / stays
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Approx 12 hours = decreases / relaxes
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Once fully established, the breaking of rigor in joints is irreversible and it will not reappear.
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Rigor mortis appearance and disappearance is accelerated by prior exercise, convulsions, electrocution or hot environmental temperature. In a hot environment, for example, the rigor mortis may disappear in only nine to twelve hours.
Algor Mortis
Under average conditions, the body cools at a rate of 2.0 F to 2.5 F per hour during the first hours, and slower thereafter, with an average loss of 1.5 F to 2 F during the first twelve hours, and 1 F for the next twelve to eighteen hours.
Livor Mortis aka Lividity
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Postmortem Lividity or postmortem hypostasis is a purplish-blue discoloration due to the settling of blood by gravitational forces within dilated, toneless capillaries of the deceased’s skin.
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Blood loss and/or anemia can cause difficulty in discerning Lividity.
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In individuals with dark skin pigmentation, Lividity in the skin can go unnoticed.
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In early stages, livor can be blanched by compression.
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In certain cases, it may be difficult to distinguish between postmortem livor and ante mortem bruises. Incision of the skin may be required.
There are many factors that affect rigor mortis, so the times listed above are only averaged guidelines. Whether a person is obese or thin and muscular play a big factor since rigor occurs in the muscles, and certain disease processes can alter the time as well. We use stages of rigor to help determine if the story we are told, as well as the scene, fits with the way we find rigor to be. For example, if we are told someone was speaking just before death, but they are stiff with rigor, we know the story is not accurate. Another example would be if the rigor was not consistent with the position the person is now observed. We cannot pin point a time of death from rigor mortis. We can only determine if it is consistent with the time frame and story we are told.
Algor Mortis
Under average conditions, the body cools at a rate of 2.0 F to 2.5 F per hour during the first hours, and slower thereafter, with an average loss of 1.5 F to 2 F during the first twelve hours, and 1 F for the next twelve to eighteen hours. As with rigor mortis, algor mortis times are a guideline and not exact. A person’s condition (such as body fat or disease) can play a part in how quickly – or slowly – their temperature drops. If they are on a pillow top mattress they will stay warmer longer because the pillow top retains body heat. If they are inside but near an open window and with cold air blowing in, they will cool down faster. If we know someone has been deceased for awhile – such as several hours – but they are outside and their temperature is still very high, and especially if it is higher than normal, then we must consider heat exposure as a factor in their death. This can occur inside too, when someone does not have adequate temperature regulation and it is very hot outside. If it is very cold, and the decedent is inadequately dressed or outside, then we use their temperature to help determine if exposure to the cold could be a factor in their death.
Livor Mortis or Lividity.
Postmortem Lividity or postmortem hypostasis is a purplish-blue discoloration due to the settling of blood by gravitational forces within dilated, toneless capillaries of the deceased’s skin.
Blood loss and/or anemia can cause difficulty in discerning Lividity. In individuals with dark skin pigmentation, Lividity in the skin can go unnoticed. In early stages, livor can be blanched by compression. In certain cases, it may be difficult to distinguish between postmortem livor and ante mortem bruises. Incision of the skin may be required.
Lividity is often mistaken for bruising by the untrained. One of the ways we check lividity, is by applying moderate pressure with a finger. If the pressure is able to change the color to white, we consider that “blanching” and lividity is NOT set. If the coloring does not change, then we consider the lividity “set” or “fixed.” (see pic)
Occasionally we will see some lividity on both the anterior (front) and posterior (back) of the body. This indicates the body had been in a position for awhile, then moved to another position. If we are told the decedent was NOT moved, then our findings contradict the story. This is important, however it is not unusual for someone to find their loved one face down and roll them over when they don’t respond. If they admit this up front, then mixed lividity would not be as surprising. Lividity can often tell us where the person had been laying. See the photo inserted. You can see where the decedent had been lying on a flat service causing part of their back to not have lividity.
In an investigation, we use each finding as part of the puzzle of what happened. By checking many different factors, we can discover if there is something that does not fit with the story and/or the other findings. This helps us determine if there is something suspicious in what might otherwise appear to be a nature or non-criminal death.
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