Biology Presentation 2013

8/12/2019 Biology Presentation 2013

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IOLOGY


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The application of science to the law/criminal investigations.It applies the knowledge and technology ofscience for the definition and enforcement ofsuch laws.Extremely popular these days especially ontelevision

- CSI

- Law & Order- Forensic Files etc


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Several persons involved in the developmentof forensic science

Leone Lattes(1887-1954)Devised a relatively simple procedure fordetermining the blood group of a driedbloodstain, a technique that he immediately

applied to forensic science.


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Edmond Locard(1877-1966) Locards xchange Principle

The exchange of materials

between two objects that occurswhenever two objects come intocontact with one another

Basically: Every contact leaves a

traceThis is the basis of forensic science


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Can be a room or a large open lot Very important and must be managed properly The first officer on the scene is critical because

he secures the scene (cordon off) and calls thenecessary specialists ( forensic scientists,

pathologist, bomb squad etc) Log book must be kept at the scene to register

who goes in and out. Must be properly documented and recorded

(sketches, photos etc) and pictures of evidencetaken.

The chain of custodybegins here. Point ofcollection to when it gets to Court.


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Physical evidencecan be found here i.e. anyobject that can establish a crime has beencommitted or can provide a link between acrime and its victim or between a crime andits perpetrator

SOC

Victim Accd/Susp


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Types of Crime Scenes:

Sexual Assualt- hair, semen, blood,fibres

Murder- blood, fingerprint, firearmand ammunition, knife

Drug Raids narcotics, packages,chemicals

Arson- empty gasoline bottles,molotov cocktails (bottle bomb)

Fraud- documents, counterfeit Robbery- tools, paint chips, fibres, glass


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Bloodstain Pattern Analysis:is the examination of the shapes,

locations, and distribution patterns ofbloodstains, in order to provide an

interpretation of the physical events

which gave rise to their origin.

Based on the prem ise that al l

b loodsta ins and bloodsta in pat terns

are character ist ic o f the forces that have

created them.


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Bloodstain Patterns are classified as:

i) Passive Bloodstains patterns - results from

blood that has fallen due to gravity


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A transfer bloodstain is created when a wet, bloody

surface comes in contact with a secondary surface. A recognizable image of all or a portion of the

original surface may be observed in the pattern, as

in the case of a bloody hand or footwear.


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Transfer bloodstains can befurther subdivided into:

Contact bleedingSwipe or SmearWipe

Smudge


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Cast-off StainsBlood released or thrown from a blood-bearingobject in motion:


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Arterial Spurt / Gush

Bloodstain pattern s) resulting from bloodexiting the body under pressure from abreached artery:


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Projected Bloodstain patterns

results as theblood source is impacted by some external forcegreater than gravity

It can be internally or externally produced

The size, shape, and number of resulting stains willdepend, primarily, on the amount of force utilized to

strike the blood source.


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MEDIUM VELOCITY

Force of 5 to 25 feet/sec.Preponderant stain size 1 to 4mm in size


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HIGH VELOCITY

Force of 100 feet/sec. and greater

Preponderant stain size 1mm in size and smallerMist like appearance


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Altered Bloodstain patterns - results fromblood that was physically or physiologicallychanged

Altered Bloodstain patterns are :- Clots

- Diluted stains

- Stains altered due to insect activity

- Patterns created as a result of obstructionby an object


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Protection be contamination conscious

Procurement collected evidence mustcoincide with documentation.

Package methods should not in any wayimpede or prevent testing.

Preserve ensure proper storage


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Kastle Myer Test

Luminol

Precipitin

Marking of exhibits


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Kastle meyer Test

The test are based on the peroxidase likeactivity of the haemoglobin in the blood.

The presence of Haemoglobin will acceleratethe oxidation of the phenolphthalin in thepresence of hydrogen peroxide.

Colourless reduced phenolphthalin is oxidisedto pink phenolphthalein.


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Kastle- Meyer Kit


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LUMINOL

A Chemical that reacts with the

Haemoglobin molecule in the blood toproduce different molecules andproduce light.

The light is only detected in darkenedareas


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BLOOD

Determine the species of blood found : is it human

blood? PRECIPTIN TEST is an immuno-electrophoresis

reaction


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Precipitin :An antigen antibody reaction

Antigen any substance that stimulates an

immune response ( human blood)

Antibody a specific protein produced by theimmune system in response to an antigen (anti-

human sera)

The antibodies react with antigens to form a

precipitate


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Preci itin Electro horesis Tank


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Confirming Human blood

Precipitate confirming that

blood source is human


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CONFIRMATION TESTING

BLOODSeratec Hemdirect Assay


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Bloodstain Item of clothing


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Item with mixture of Blood and Semen


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Weapon


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Weapon


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Acid Phosphatase Test

Microscopic Test for

Spermatozoa


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Acid Phosphatase Test

Acid Phosphatase is an enzyme found in high

concentration in semen

Naphthol is liberated from the alpha napthyl

phosphate and reacts with diazonium compound

(Fast Blue) to form an insolouble coloured product


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Semen stains turns purple


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Vaginal

Anal

PenileOral/Buccal


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VAGINAL SWAB AND SMEARS


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Microscopic analysis is done to identify : Red blood Cells

White Blood Cells / Pus cells Spermatozoa

N. gonococci

red blood cell

Pus cells


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Pus cells with gonorrhea causing


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gonococci

Pus cells with gonorrhea- causing

bacteria


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Trichomonas vaginalis


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Azo-spermic males or males with extremelylow sperm count (oligo-spermic) due todiseases or defects or males that had a

vasectomy may not have spermatozoapresent in seminal fluid.

Confirmation Testing


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Confirmation Testing

SEMEN

PSA p30 Test kit

a rapid test identifying prostatespecific antigen (PSA)


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Sweat

Urine

Saliva Faecal matter (semisolid)


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Alpha () amylase is the enzyme found in highconcentration in saliva

Alpha () amylase is also found in highconcentration in faecal matter and pancreatic

juices


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Starch Iodine Test

Starch reacts with Iodine to produce a blue-blackcolour

The salivary alpha () amylase in an extract of

saliva stain will when added to starch solution

break down the starch to maltose and dextrins

Addition of iodine to this resulting solution will notproduce a blue- black colour. This is a positive

result.


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Phadebas Test

A colourimetric commercial test


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Phadebas Test

Phadebas reagent is comprised of starch being

linked or attached to a coloured dye to form starch-

dye complex.

In the presence of salivary amylase the starch is

hydrolyzed (broken down) and the dye is released

Blue dye form a blue stain in the area where saliva

is present


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The basis of the test is to identify the presence of

creatinine

An extract is made of the stain by adding water

One drop of pictric acid and one drop of 5%

sodium hydroxide

The formation of a brown orange colour indicate

the presence of creatinine


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Natural or synthetic Race of person Type of animal If root is presentthen DNA analysis

Natural or synthetic Class of syntheticfiber Colour comparison Texture comparison


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NEGROID

CAUCASIAN

ASIAN


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Biology Presentation 2013