How to determine time of death
when a deceased person passed. The time of death calculator is a crucial piece of
information and a tool that is used to measure the time that has passed between a
person death and the detection of his body.
The two important factors for determining the time of death are –
Calculating the time of death using algor mortis (change in
the temperature of the body) and
Calculating the time of death using rigor mortis (change in
the rigidity of the body).
Algor Mortis
The cooling of the body after death is Algor Mortis. As we know that the Normal
body temperature is sustained by blood circulation and when our heart stops the
circulation automatically stops resulted in cooling of body. A normal body temperature
is 98.6 degrees F (37 degrees C) but it may vary. Two terms are important in
calculating the body temperature of the deceased -
The ambient temperature – It is the temperature of the surroundings where the
body was found (e.g., the air temperature) and
The body temperature - The body temperature measured in the
rectum /rectally.
The formula is started by taking body’s temperature rectally. After several hours
one’s heart has stopped beating and the body’s core temperature drops near to
ambient temperature (i.e. room temperature, if indoors). The body loses 1.5 degrees
Fahrenheit per hour, so rectal temperature is subtracted from the normal body
temperature that is 98 degrees F, again divided the difference by 1.5, and that
final number is used to approximate the
time since death.
Time since death = (98.6 – Rectal Body temperature) / the
1.5-degree-per-hour factor
The deceased body loses heat passively by three mechanisms –
Radiation – Body heat lost as infrared heat rays,
Conduction – Body heat passed on to any object that contacts
the body, and
Convection – Body heat lost into the moving air.
The 1.5-degree-per-hour factor works if a number of factors
are expected to be constant, like the ambient temperature hasn’t changed since
the death… or when we found the victim was in clothed and in the air rather
than in a bathtub full of water. Alcohol consumption by the deceased before
death, the size of the corpse and other factors also interferes with body’s
cooling process. A deceased body in a temperate room will drop heat much more
slowly in comparison to one in an icy or flowing stream. The body will lose or
gain heat until it touches equilibrium with its environment. Heavy clothing,
Obesity, warm still air, exposure to direct sunlight and an enclosed
environment slow down the heat loss. Chronically ill or emaciated person dead body
loses heat slowly as compared to body of elderly and children. When the body is
in contact with cold surface ( marble or cool concrete), heat loss will be
greater.
Liver mortis is when heart stops beating, blood stops
circulating, resulted in purplish-blue discoloration of the skin due to the
collection of blood in skin vessels due to gravity (pooling into the parts of
the body closest to the ground).
Blanching is what happens when you press your finger on your
skin and you see for a few seconds a white spot appear.
This lightening of the skin is due to pressure of your
finger pushing the blood away from that area for a few seconds creating a lack
of blood in that area. The blood rushes back after pressure is removed. When
livor mortis has fully set in, blanching totally ends. The discoloration of the
skin becomes ‘fixed’ after a certain period, owing to the breakup of blood
cells and the leak of hemoglobin. After 2 to 4 hours of death livor mortis
starts to progress and it becomes non-fixed or blanchable up to 8 to 12 hours and
fixed or non-blanchable after 8-12 hours from the time of death.
At the crime scene Investigator will press his finger in an
area of pooled blood to see if the area is fixed or not to further determine
the time of death. In addition to the pooling of blood, petechial hemorrhages
or Tardieu Spots also starts( small vessels breakdown throughout the body). If
the markings of livor mortis don’t resemble with the position the body, it
indicate that the body has been moved.
Livor mortis is less helpful on bodies found days or weeks
after death as it does not have very precise measurement of the time of death
after 12 hours.
Rigor Mortis
Stiffening of muscles after death is Rigor mortis. It is caused
by the reduction of adenosine triphosphate (ATP) from the muscles. The stopping
of oxygen supply causes the stoppage of aerobic respiration in the cells and
leads to a lack of ATP production. Buildup of acid in the muscle tissues
resulted in stiffening (not contract but just lock in place) of body in next 24
to 48 hours.
Rigor mortis first appears in smaller muscles over the face,
head, around the eyes and the jaw followed by rigor mortis of the muscles in fingertips,
neck and upper limbs, then moves to large muscles of the lower limbs. Rigor
mortis sets for 18 to 36 hours and then disappears, followed by a phase known
as secondary flaccidity.
In general –
Death occurred under 3 hours, the body feels warm and no
rigor is present.
Death occurred under 3-8 hours, the body feels warm and
stiff.
Death occurred under 8-36 hours the body feels cold and
stiff,
Death occurred more than 36 hours; the body is cold and not stiff.
Factors that impact the onset and timeline of Rigor mortis
are –
Temperature- The rate of rigor (hot) either increase or slow
down (cold) by the effect of temperature around the body.
Illness – Ill person body already have increased amounts of
acid in the muscle tissue (higher concentration) which will increase the rate
of rigor.
Activity before death - Strenuous activity before death also
increases the amount (concentration) of acid in the muscles resulted as increase
the rate of rigor.
Physical conditions where the body is found – A change in
the rigor timeline affected by other environmental aspects like movement of the
body once rigor has set in. If the body was forced to move or bend despite
being stiff, the process of rigor is broken and will not reform back to normal
standards.
Once ambient temperature, livor mortis and rigor mortis are
all in place, determining time of death becomes trickier.
MR. DEEPAK PAWAR has been working as Finger Print Expert / Police Officer in Finger Print Bureau , Delhi Police at New Delhi since 2001 . He is the senior most Finger Print Expert , attending / visited several scene of crime and solved many crime cases .He has passed M.Sc (Chemistry) and he is the Member of International Association of Identification . He is the Member of Delhi Police welfare association . He is supervising the Forensic , New Delhi District , Mobile Crime Team . He is one of the Expert in the Special Investigation Team held for investigation of important cases . He has been giving fingerprint proficient training to Delhi Police personnel's . He has been Presented / giving lectures on topics related to forensic science . He is also making examination paper of Finger Print proficient course . He is awarded with Police Medal by MHA and Delhi Police.