FORS-2106EL Lecture Notes - Lecture 12: Acetic Acid, Heme, Reducing Sugar
27 Jun 2018
School
Department
Course
Professor
Forensic Biology - Day 12 2017.11.02.
-exam
-first section 30 definitions, 2 marks each
-short and long answer questions
-procedures, steps, concepts, and textbook topics
Forensic Serology: Blood Identification
-blood leading event: general term for bleeding
-this was a problem for officers as there could be a lot or a little
-when there’s a lot, it is easy to tell if it is blood or not
-when there was not a lot, you must test to check if it blood or not
-a presumptive test will test for negative or positive of a sample, vs a controlled
sample
-these could give false positive, that will come with the test to ensure you are aware
of the possibility of this
-there is no more dangerous substance that you can encounter, then blood due to the
diseases blood can carry (bacteria, prion (no cure) , viral)
-mad cow disease: brain begins to become spongy and break down (BSE)
Intro
-purpose: to identify liquid and dried substances as being blood or not
-prior to DNA fluids were in the purview of forensic serologists
-blood at the scene:
-indicates blood-letting by victim and/or perpetrator
-you can find blood in almost every single bathroom due to the fact that we release
blood in many ways, so viewing the context of the blood is important
Serology
-They are big on blood type (class physical evidence)
-Blood analyzed to ascertain its source
-Connection between the blood and the victim and/or perpetrator using class physical
evidence
-perpetrators can get cut by hand sliding on blade in stabbing, and defensive
wounds
-Forensic contexts deals with fresh, dried, and degraded samples
-You will not get there fast enough to get liquid blood, most of the time it will be dried
or sucked into a source
-degraded occurs when its so dry that it can be pealed in flakes
-Quality and quantity of the sample dictates the how it will be dealt with
find more resources at oneclass.com
find more resources at oneclass.com
Degradation Factors
-Heat
-destroy the DNA with heat, even sun
-Humidity
-moisture can cause alterations to the blood
-can become greenish colour from bacteria breaking it down
-Careless handling of dried stains
-dried stains flaking
Identification Protocol
-Visual examination for stains
-position, condition, does it make sense, how is it deposited, was it transferred
through touch, did someone smear it (a blood wipe), transferred through blood
source
-Presumptive test of the stain
-will give a positive or negative result, using a controlled sample, another area of the
material where you see no blood, then test the stain itself to see if positive or
negative
-Specific test to confirm blood
-can test for blood types
-h is an antigen we all have, but we still test for it to tell us if the blood is degrade,
because if this comes back negative then you know the blood is not intact enough
to test
-Then it will be tested for A and B, as well as Rh + or -
-Determine origin
-blood type will give us class evidence for finding the origin
-Characterization genetically
-you can do DNA analysis to find where an exact allele comes from
Presumptive Tests
-Positive or negative
-Positive: qualified conclusion
-there is a caveat (warning) on this conclusion, so it is positive but it is not 100%
certain something else may not have reacted with it
-Negative: elimination of sample
-if reagents are 100% effective, this test will exclude the possibility of blood
-Typically done using a colour test or production of light
-chemiluminescence using spray
-Blood has catalytic properties that make these tests possible.
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Rst section 30 de nitions, 2 marks each. Blood leading event: general term for bleeding. This was a problem for of cers as there could be a lot or a little. When there"s a lot, it is easy to tell if it is blood or not. When there was not a lot, you must test to check if it blood or not. A presumptive test will test for negative or positive of a sample, vs a controlled sample. These could give false positive, that will come with the test to ensure you are aware of the possibility of this. There is no more dangerous substance that you can encounter, then blood due to the diseases blood can carry (bacteria, prion (no cure) , viral) Mad cow disease: brain begins to become spongy and break down (bse) Purpose: to identify liquid and dried substances as being blood or not. Prior to dna uids were in the purview of forensic serologists.
