post mortem interval

Post-Mortem Interval

Algor Mortis

• the loss of body heat in the corpse

  • as a general rule the body loses heat by 1 ½ degrees fahrenheit per hour until the body reaches the environmental temperature 

• body temperature is highly variable, important factors include:

  • ambient environmental conditions 

  • body habitus (e.g., thin or fat) 

Liver Mortis (lividity) 

• caused by the setting of the blood (as a result of gravity) in the small vessels of the circulatory system

• once “fixed” a change of body position will not result in alteration of the liver mortis patterns

• liver mortis may help the investigation by recognizing subsequent manipulation of the body after death (e.g., when the pattern is inconsistent with the final position)

Rigor Mortis 

• rigor appears within two hours of death, becoming greatest at 8-12 hours after death. it will disappear generally within 36 hours after death

After Death, two decomposition processes take place:

• autolysis

• putrefaction 

  • typically manifest itself in the abdomen as 

    • swelling of tissues/bloating 

    • foul smell

    • black or blue discoloration of tissue

    • protrusion of the eyes or tongue 

    • ultimately resulting in slippage of skin and purging of fluids

Decomposition 

• major factors include environmental conditions, including temperature and humidity  

Forensic Entomology 

• entomological (insect) activity will begin in and around the body very quickly after death (twenty minutes) 

• The various insects involved in this activity have defined life cycles, which if properly noted may assist in defining the post mortem interval 

• the primary insects of interest include:

  • blow flies 

  • beetles 

  • wasps

• These determinations are not straightforward, however. The time required for stage development is affected by environmental influences such as geographical location, climate, weather conditions, and the present drugs. 

Fly activity 

• flies will begin laying eggs on an exposed corpse within 20 minutes of death 

• they lay eggs in and around moist opening: 

  • nostrils 

  • corners of the eyes

  • mouth

  • open injuries 

  • any other opening that is exposed

• by observing and collecting the various stages of flies present on the body and in the scene, an entomologist may be able to estimate the post mortem interval