Topic 3 biochemical analytical technique part 1 Flashcards
explain forensic entomology in criminal investigation
- it denotes the study and application of insects as evidence in a legal investigation.
- it is done by studying the insect population and developing larval stages
- can estimate the post-mortem index, any change in position of the corpse as well as the cause of death
what is the role of a forensic anthropologist in criminal investigation? and what are the three types
forensic anthropology is the study of skeletal remains that involves applying skeletal analysis
the 3 types:
- FUN dating
- fluorescence spectroscopy
- carbon-14 dating
describe FUN dating
bone nitrogen content fresh bone = 4% weight decreases with age
bone fluorine and uranium content of fresh bone = 0% increases with age (from ground water)
- only useful for skeletal remains less than 100 years old
- only useful for comparing samples from the same site, fluorine and uranium in ground water/ minerals vary from one site to the other
describe fluorescence spectroscopy
indicates remains are 100 years old or more
describe carbon-14 dating
- for very old human remains (>400,5000 years old)
limitations
- not very accurate for <500 years old (amount of ^14C decay too small)
- cannot be used for samples deposited since 1950 due to nuclear bomb testing
used to examin skeletal remains such as
- the BOG people
- the body in the ice: otzi
- the lindow man
what is bloodstain pattern analysis (BPA)?
-> it is the interpretation of bloodstain at a crime scene in order to recreate the action that causes the bloodshed.
role of FS:
to assist in reconstruction of those events of an alleged incident that could have created the stains and stains patterns present at a crime, on items of physical evidence recovered from that scene and on items of clothing that were present at the crime scene. analysts examine what did or did not happen
what are the 3 types of blood patterns ?
- passive bloodstain
- projected bloodstain
- transfer or contact bloodstain
what is passive bloodstain ?
patterns created simply from the source of gravity
what is projected bloodstain ?
patterns that occur when a force is applied to the source of the blood
examples include:
- low/medium/high impact spatters
- arterial spurting
- expiration blood blown out of the nose,mouth or wound
what is transfer/contact bloodstain?
when a wet, bloody object comes into contact with a target surface
- this can be used to identify an object or a body part
describe latent fingerprint
-> a fingerprint left on a surface by deposits of oils and/or perspiration from the finger
- when a fimgerprint is found a crime scene, it is usually known as a ‘latent fingerprint’
- it is usually not visible to naked eye
what are the 3 principles of fingerprints
1st principle: no two fingers have the same prints INCLUDING identical twins
2nd principle: fingerprints do not change during a lifetime (and remain after death for some time)
- it might fade away due to ageing scarring or genetic issues
3rd principle: patterns can be classified
what are the 3 types of latent fingerprint visualisation (qualiattive analysis)?
- dusting power
- types of powder:
A. molybdenium disuphide
B. aluminium
C. carbon black
- choose powder according to background contrast
- chemical visualisation reagents
- ninhydrin (apply and heat) reacts with amino acids
- iodine sprays
- silver nitrate - alternate light source
- alone or using a dye
describe Fourier transform (FTIR) microscope
- FTIR coupled with a high resolution microscope
- non-destructive qualitative and quantitative technique
- analytical tool to visually and chemically analyse illicit tablets, hairs, fibers, inks and paints found in a crime scene
describe electronic databases
not rly impt
- fingerprint database - criminals
- give close matches but not perfect matches
- human judgement is still required
