Investigative Techniques To Determine Time Of Deat

Essay, Research Paper

Investigative Techniques to Determine Time of DeathOne of the first steps involved in a homicide investigation is the determination of the time of death. While knowing the time of death is not crucial in each and every homicide case, it can be of significant importance in some. Except for a bullet passing through a victim’s head and striking a clock in the same room, determining time of death is not an exact science. However, there are a number of different indicators, most of which are evaluated during the autopsy, that can estimate the time of death to within hours. Accuracy will depend on such factors as the condition of the cadaver and its state of decay. Beginning at the crime scene, police officers can make a preliminary determination of the time of death by the body’s appearance and surroundings. Factors such as indicative acts, postmortem body temperature (algor mortis), postmortem lividity (livor mortis), stiffening of the body (rigor mortis) and putrefaction can all help to roughly estimate the time of death. Later, during the autopsy, forensic pathologists can examine more closely the above information as well as other factors such as stomach contents, chemical changes within the body, and insect activity, also known as “forensic entomology”. Starting at the crime scene, an investigator might look first at the indicative acts of the deceased. (O’Hara, 538)Indicative acts are those activities which the deceased may or may not have performed before death. If the victim is found in his or her home, non-medical evidence such as dates on uncollected newspapers, the condition of food in the house, or other customary acts not performed may give a relatively close estimate on time of death. In an outdoor crime, something such as the area underneath the body being unaffected by rain or snow could also set certain limits to the time lapse since death. (O’Hara, 540) However, probably the most reliable form of non-medical evidence are the statements of witnesses. (Hendrix, 19) If indicative acts or other non-medical evidence are not sufficient, then more scientific methods must be used, such as determining the postmortem temperature. Algor mortis, which means “the temperature of death” describes the cooling of the body. In ideal conditions, the rate at which a body cools is one degree per hour. However, factors such as the air temperature surrounding the corpse, body fat content, or immersion in water will cause the estimate to vary greatly. The following chart is based on a careful study of cadavers in a controlled environment with temperatures ranging from 59 to 68 degrees Fahrenheit:Rectal Temperature Time in Hours to Reachof the Cadaver the Indicated Rectal Temp. Minimum Maximum93 2 690 3 986 4 1282 6 1579 9 2075 12 2472 18 30This table shows that accuracy in pinpointing time of death decreases as the body’s core temperature decreases. Obviously, a span of 18 to 32 hours will be of little help to an investigator. (Wilber, 38). Fortunately, there are other methods to rely on, such as postmortem lividity. Livor mortis, which means literally “the color of death” is the discoloration of the skin caused by flow of blood into the venous spaces under the influence of gravity. Simply put, it is the blood pooling or settling into the lowest portions of the body. Livor is not considered to be a good indicator of postmortem interval, but there are some standards which can be seen. (Hendrix, 21). Anywhere from one-half to one hour after death livor can begin to be seen. Its appearance is similar to a bruise. In the early stages of lividity, (less than four hours) the skin, unlike a bruise, can be blanched when pressed. After four hours, the lividity has begun to set, and by six to ten hours, it has reached its maximum and is permanent. (Wilber, 39) Postmortem lividity is caused by the red blood cells settling into the veins and capillaries in the lowest portions of the body which causes a red color to appear in the skin beneath. Later, the red cells will break down and squeeze out of the capillaries into the body, thus making the lividity permanent. Therefore, livor is commonly used by investigators to determine whether or not a body has been moved after death. (Baden, 37) Because lividity, as stated earlier, is not a good indicator of postmortem interval, investigators may also look to another sign of death, rigor mortis. Rigor is a more common indicator of postmortem interval. Under normal environmental conditions, the muscles of a cadaver will stiffen (not contract) with a set pattern and rate. This is caused by dead muscle production of lactic acid fusing with the myocin in the muscles and forming a gel. This gel causes the stiffness. (Starkeby, Internet 1) The smaller, shorter muscle groups of the face and neck are affected first, and the stiffness gradually works its way down the body to the legs. Rigor can begin to set in fifteen minutes after death or fifteen hours after. The average time is five to six hours. (O’Hara, 539) Different temperatures can cause variations in the rate that the body stiffens. Heat will cause rigor to set in quicker, whereas cold will slow the process; therefore, these factors must be considered when making a determination of the time of death. (Wilber, 27) In temperate regions, the following rule of thumb can be used in estimating death, but it must be used with caution:If the body feels:Warm and not stiff: Not dead more than three hour