forensics lecture 7- forensic applications Flashcards
what is the purpose of a post mortem interval?
The time that has elapsed since an individual’s death
-Provide a timeline
-Support or refute witness/suspect statements
-Accuracy of estimating the time since death is negatively correlated with the time that has elapsed since death occurred.
how is post mortem interval used as evidence?
-Physical – post-mortem changes, presence of insects
-Environmental - indoor, outdoor, buried, water, burned
-Historical – victim habits/ daily routine, relationships
-Additional evidence – stopped watch, phone records etc.
what are the factors increasing the rate of cooling of the body? (algor mortis)
-small body size
-low fat content
-Body stretched out
-Body dismembered
-Serious blood loss
-Lack of clothes
-Wet clothes
-Strong air currents
-Low ambient temperature
-Body in cold water
what are the factors decreasing the rate of cooling the body?
-Large body size
-High fat content
-Foetal position
-Clothing
-Insulative covering
-Protection from draughts
-Warm ambient temperature
-Warm microclimate
-Exposed to the sun
-High humidity
what is hypostasis?
-Settling of blood due to gravity
-Pale areas (pallor) = areas of pressure
-Body positioning, items in contact, movement of body
-Not as useful for PMI
what is rigor mortis?
-Stiffening of muscles
-Caused by reduction in available ATP
-Evident in smaller muscles first
-Earliest signs 3 - 6 hours following death
-Max rigor between 6- 12 hours
-Completely disappeared by 24 – 36 hours
-Affected by temp, muscle mass, physical activity before death
what is mummification?
-desiccation of remains
-Hot dry or cold dry environment
-Skin dries out – leathery appearance
what is adipocere (grave wax)
-Favoured by damp conditions
-formed by hydrolysis of body fats
how do you calculate the PMI from the total body score?
1- find the total body score by adding the ratings of head, trunk and limbs together
2- to find the ADD then we use the equation ADD = 10 ^(0.002 x TBS x TBS + 1.81) +- 388.16
3- then use the table to find the add closest to the score to predict the estimated date of death
note= Decomp will occur down to 0oC due to salt concentrations in human body
how do you find the hours since death?
98.6oF - 92oF / 1.5 = time in hours
what is fresh stage?
Body starts to cool and autolysis begins. Hypostasis and rigor mortis may be seen.
what is the bloat stage?
Discoloration of skin surface, body swells from accumulation of gasses. Tongue protrudes, fluid expelled from orifices. Soft tissues visibly decaying. Rapid decay owing to intense microbial and invertebrate activity.
what is the active decay/putrefaction?
Tissues begin to liquify. Skin can start to blacken. Body deflates as decomposition gasses escape (purge)
what is advanced decay?
Progressive loss of skin and soft tissues. Decay owing to invertebrate and microbial activity starts to slow down once soft tissues removed and body starts to dry out.
what is dry remains/skeletonised?
Skin and soft tissues lost. Decay proceeds more slowly. Progressive loss of uterus/prostate gland, tendons, cartilage, fingernails, hair. Skeleton may become disarticulated through environmental and biological processes.
