WEEK 10! Flashcards
Why are PMC important?
They confirm death and allow the PMI to be estimated
What are the problems with PMC?
They can produce confusing artefacts, destroy evidence of injury, identify and disease.
When are PMCs useful?
In forensics
When do early changes occur?
Within minutes, hours or days
When do late changes occur?
Within weeks, months or years
What are the three early stage changes?
Algor mortis
Rigor mortis
Liver Mortis
What is algor mortis ?
- Used to estimate PMI within first 24 hours, only in temperate climates, can be problems with this when the person does not die at 37 degrees.
Reasons why a person doesn’t die at 37 degrees
Hypothermia Cardiac failure Haemorrhage Heatstroke Fever exercise cocaine
In what ways can heat be lost from the body?
Conduction
Convection
Radiation
Evaporation
What is livor mortis?
Darkening of death. Seen as pink/purple discolouration of the skin. Results in the gravitational pooling of blood in the vessels forming a horizontal fluid level.
Compression on tissue prevents blood from pooling there.
Why is livor mortis not a good PMC?
It can start before death i.e. in cardiac failure
What is rigor mortis?
Stiffening of death.
Muscles require ATP to unbind and when you run out of ATP then there is no way to unbind the muscles.
Calcium also builds up promoting binding.
Can rigor mortis be broken?
Yes and it will not return
Will a body at a higher temp get rigor mortis faster than a body at a low temp?
Yes
Timescale of rigor and algor mortis
Warm and no RM <3
Warm and RM 3-8
Cold and RM 8-36
Cold and no RM >36
Timescale of livor mortis
<6 blanching
10-2 partially fixed
>24 fully established
What are the two late stage changes?
Autolysis
Putrefaction
What is autolysis?
The enzymatic breakdown of cells and tissues it happens first
What is putrefaction?
Bacterial breakdown of cells and happens between 21-38 degrees. Bacteria from the GI and respiratory or infections. Green discolouration, swelling on the face and neck because of gas, redding fluid from the nose and mouth, skin slippage, blistering, hair slippage etc
What temp is required for putrefaction?
21-38
What are the 5 method of decomposition?
Adipocere Maceration Wet putrefaction Skeletonization Mummification
What is adipocere?
Saponification of soft tissue , requires wet conditions, transformation of body fat to oleic and appears yellow, white and brown and waxy
What is maceration ?
Sterile autolysis of the foetus
What is wet putrefaction?
Enzymatic and bacterial
What is skeletonization?
happen a long time after death
What is mummification?
Desiccation of soft tissues, occurs in cool dry conditions, skin dries and shrinks and becomes leathery.
What is a injury?
Damage causes by heat, cold, electricity, chemicals and radiation
What is a lesion?
Any area of injury, disease or local degradation in a tissue causing a change in its structure or function
What factors effect the injury?
Degree of force Areas of application Duration Direction Tissue properties
What is the Ek?
Kinetic energy, E=1/2 mv^2
What considerations should you make when determining the cause of an injury?
Superficial or deep Areas of perceived harm Accessibility of area Fatality hesitation Concealment
What are the different types of mechanical force that can cause an injury?
Impact Angulation Compression Traction Torsion Shearing Acceleration
What is a blunt force wound?
Injury caused by contact with a blunt instrument. Normally occur together.
Types of blunt force injury?
Abrasion
Bruise
Laceration
What is an abrasion?
Superficial/partial thickness skin injury. Not clinically significant but important in forensics. Often imprint abrasions.
What are the 3 types of abrasion?
Imprint - Crushing vertical force
Scraping - Tangential force
Graze - Board surface (i.e. road rash)
What is a bruise of an organ called?
Contusion
What should you always consider about a bruise?
May have moved, colour doesn’t tell you anything (red is new kind of)
What are the different types of bruise ?
Patterned bruise - Mirror image of the weapon
Examples of patterned bruising
Tram-tracks
clustered discoid
Black eye
What is a laceration?
Cut or tear in the skin due to crushing or rotation. Ragged edges inc. tissue bridges
What are sharp force wounds?
Occur by themselves and after contact with a sharp object.
What are the two types of sharp wound?
Incised
Stab
What is an incised wound?
Superficial from slicing etc. Longer than deep Knife usually Clean edges Lots of bleeding
What is a stab wound?
Deeper than long
Bleed a lot
Clean edges
slit or concave if against the grain of the skin
What are chop wounds?
Hybrid of blunt and sharp Heavy bladed instrument Occur along side many other types of wound often cause bone fractures normally longer than deep
What is clinical biochemistry?
The study of changes in chemical composition of body fluids
What is histopathology?
Study of diseases
