forensics

Question 1

different blood group systems

Answer 1

ABO blood group
rhesus
MNS

Question 2

what are secretors ?

Answer 2

75-85% of the population.
- are indivudlas who secrete blood group antigens (ABO) into bodily fluids eg saliva
however more susceptible to norovirus

Question 3

good and bad sources of DNA

Answer 3

good source- what blood cells
-sperm cell (semen) and vaginal fluid
-hair with root

bad source- skin cells (dead)
-urine (DNA degraded due to PH)
-hair shaft
-faeces (bacteria)

Question 4

DNA profiling methods

Answer 4

autosomal STRs-
slight DNA deviation not a problem
-small sample size
-excellent discrimination

autosomal SNPs-
maintained in a population and have no effect on amino acid
-very small sample size can be used and can be inherited ancestry

Question 5

what is a DNA profile database?

Answer 5

dna sample is taken and turned into DNA profile database.
only people on the database are people convicted of a crime, if proven innocent there database is removed.

Question 6

why examine STR patterns of several loci?

Answer 6

by examining several loci can get a better profile as some may be degraded.
more effective allele frequency comparison within a population
less coincidental matches

Question 7

the analysis of low copy number DNA (LCN)

Answer 7

DNA available is very small
- copies 10 STR regions (takes longer)

Question 8

What is partial profiling?

Answer 8

obtaining DNA from a sample which not all loci are present eg DNA has degraded.
use LCN profiling

Question 9

what is familiar searching in partial profiling?

Answer 9

if you have a full DNA profile but no matches on DNA database, look for similar DNA profiles eg age, ethnicity

Question 10

what is forensic entomology?

Answer 10

study of insects to aid legal investigations.

Question 11

what is metaphorphosis and why is it important in forensics?

Answer 11

we rely on insects going through development in a predicted pattern.
very temperature dependent (warm occurs fast) (cool occurs slowly).
helps predict span on when someone died

Question 12

what is succession in forensics

Answer 12

insects arrive in a set pattern. The type of organism which can be found on a body change over time

Question 13

4 ways invertebrates are associated as forensic indicators ?

Answer 13

1) detrivores attach to dead bodies (break down and decay body)
2) invertebrates leave the body when it stops working
3) invertebrates can be accedendly associated with crime scene eg caught in clothes

Question 14

stages of decomposition for insect succession?

Answer 14

fresh- blowfly law eggs

bloat- blowfly eggs are more developed as more food available. burying beetles occur for body decomposition

purification- eggs have advanced, no blowfly’s and phorid flys mop us loose liquid

dry remains- no blowflies.

Question 15

succession/ lifecycle of blowfly

Answer 15

1) adult blowfly arrives to body within minutes and lay around 300 eggs in wounds

2) within 24 hours eggs hatch and enter 1st instar stage (how long insect has been on the body)

3) feed, moult to 2nd instar larvae
feed moult to 3rd instar larvae
feed moult to prepupae larvae, then move away from body and restart as adult blowfly

Question 16

how to establish PMI using insects

Answer 16

21hours- ist instar
31 hours- 2nd instar
26 hours- 3rd instar
as larvae was found mid 3rd instar that’s half developmental time = 50/2=25

calculation-
21+31+26+25+48(hours after death)
=151hours= 6.29 days

range between- 126 and 176 hours

Question 17

calculation for estimating hours since death?

Answer 17

98.6- corpse core temp. / 1.5

Question 18

factors affecting the rate of body cooling (algor mortis)

Answer 18

-small body size
-low fat content
-body stretched out
-serious blood loss

Question 19

definition of hypostasis and rigorous mortis

Answer 19

hypostatis- settling of blood due to gravity
-pale areas

rigor mortis-
stiffening of muscle due to the reduction of ATP. occurs 3-6 hours after death and max 6-12 hours

Question 20

5 stages of decomposition?

Answer 20

1) fresh dead= body cools= hypostasis and rigorous mortis

2) bloating= discolouring skin and body swells due to gas build up

3)active decay/ putrefaction=
skin blackens and body deflates

4) advanced decay= invertebrate and microbial decay slow down due to loss of skin and soft tissue

5) dry remains/ skeletonised=
skin and physical features lost

Question 21

visible decay features

Answer 21

-green discoloured skin
-skin slippage (epidermis from demas)
-MARBLING
-BLOAT

Question 22

decomposition phenomenas in different environments (mummification and adipocere)

Answer 22

mummification- occurs in hot dry or cold dry environments. skins dry out

adipocere- occurs in damp conditions due to the hydrolysis of body fat

Question 23

look at notes to calculate PMI based on total body scoring (TBS) and accumulated degree days (ADD)