Forensics Flashcards
What does body temperature drop by every hour after death?
Roughly 1.5 - 2 degrees
How is body temperature measured?
Rectally or by measuring liver temperature
What is rigor mortis?
Stiffening of the body
How long after death does rigor mortis set in?
4 - 6 hours
Why does rigor mortis occur?
.No oxygen, anaerobic respiration produces lactic acid, this decreases pH in muscle cells. Denaturing the enzymes that produce ATP
.No source of ATP after death so myosin heads attached to actin can’t detach, leaving muscles in contracted state
What 4 factors alter the time taken for rigor mortis to set in?
-Muscle mass
-Temperature
-Activity before death
-Body fat
3 factors that alter reduction in body temperature:
-Body fat
-Position of body
-Clothing
What is forensic entomology?
The study of insects feeding and living off a corpse
Why do tissues break down after death?
Lack of oxygen so cells stop respiring
What 2 conditions influence rate of decomposition?
Amount of water
Temperature
Stages of succession for insects:
1) Bacteria will be found in body immediately after death
2) Flies then lay eggs and larvae will hatch
3) As more soft tissue is consumed by fly larvae it creates favorable conditions for beetles to establish
4) Beetles can decompose dry tissues
5) Once all tissues have been decomposed most organisms will leave the body
What is DNA profiling?
Process to identify individuals based off patterns in the DNA
What is satellite DNA?
Very large bands of non-coding DNA (introns)
What separates strands of DNA into fragments (PCR)?
Restriction endonucleases
What is polymerase chain reaction?
Technique used to make large fragments of DNA from a small quantity (DNA amplification)
What is a primer?
Short pieces of DNA that will attach to the end of the DNA being copied
3 stages of polymerase chain reaction:
.Denaturation - Temperatures raised to 95 C which breaks hydrogen
bonds that hold DNA strands together
.Annealing - Temperature decreased to 50-60 C so primers can attach to ends of single strands of DNA
.Elongation - Temperature increased to 72 C (optimum temperature for Taq polymerase which is high), will build complementary strand of DNA to produce new identical double-stranded DNA
How does gel electrophoresis separate DNA?
Use of electric current in gel, DNA is placed in the cathode end and because it’s negatively charged DNA will move towards the anode end (positive).
What 3 things can be compared in different DNA profiles?
Number, width and position of bands
How can you estimate time of death of a human based on changes in inspect species on a pigs surface? (3 marks)
.Record which insect species are present on human
.Compare with results of investigation from pigs to determine time of death
.Keeping environmental variables the same
Describe the changes that occur inside a body in the first week after death. (3 marks)
Body temperature falls
Stiffening of muscles
Bloating, accumulation of gases
