Midterm Exam Study Guide: Biological Evidence

Chemiluminescence

Are designed to detect trace amounts of blood • These assays use an oxidation-reduction reaction which is catalyzed by a heme. • Heme is a component of hemoglobin • The reaction with the heme causes colorless substrates to undergo an oxidation reaction that results in a change of color, fluorescence or chemiluminescence.

What are the subdisciplines of forensic science

Crime Scene Investigation Pattern evidence analysis Forensic Biology Toxicology Trace evidence analysis Controlled substance analysis Fire/explosion debris analysis Questioned document analysis Computer forensics Forensic Pathology

Amylase

Enzyme in saliva that breaks the chemical bonds in starches. Enzymes that cleave polysaccharides such as starches

Antigen

Is a foreign substance that is capable of reacting with an antibody

CODIS (Combined DNA Index System)

Is a national DNA information respiratory maintained by the FBI that allows state and local crime laboratories to store and compare DNA profiles from crime-scene evidence and convicted offenders

Locard's Exchange Principle

Is a theory that cross-transfer of evidence occurs whenever a perpetrator has any physical contact with an object or person. • This is the theory that trace evidence analysis is based on.

Amylopectin

Is highly branched and consists of linear chains of glucose residue branched starch

parts of a blood droplet

Spines satellites tails

Primary reactions

Is the initial binding of 1 epitope of an antigen (Ag) to 1 binding site of an antibody (Ab) to form an antigen-antibody complex. • This is a rapid and reversible reaction• This type of reaction can be measured by techniques such as enzyme immunoassays, immunoflourescence, radioimmunoassays and dye-labeled immunochromatography.

Kastle-Meyer test

It will turn PINK in the presence of blood!

Gunshot injury

Mist‐like spatter caused by bullets entering and exiting the body/entrance wound and exit wound

Read results of RSID kit

negative-line on C Positive-line on C T Invalid-line on T

why there

death penality

Where was it prosecuted

new hampsher

Y chromosome inheritance

direct passing from father to son

mtDNA is inherited from

only the mother

three basic types of bloodstains

passive stains -transfer stains -projected or impact stains

Kary Mullis

polymerase chain reaction. Developed a technique that amplifies a small quantity of DNA

polyclonal antibodies

re produced when an immunogen is introduced into a host animal such as a bird (B), rabbit (R), or horse (H). • These antibodies can either be circulating in the blood or attached to tissue. • Circulating antibodies are also called humoral antibodies.

Cast-off spatter

resulting from blood drops released from an object due to its motion/bloodstain pattern created when blood is flung from a blood-bearing object in motion onto a surface

Semen is composed of

seminal fluid and sperm cells

Most abundant secretion in seminal fluid is

seminal vesicle fluid which accounts for about 60% of the total ejaculate amount

Different types of linkages that evidence can help establish

victim-to-perpetrator established with evidence found at crime scenes such as victim-to-scene or perpetrator-to-scene Blood or other bodily fluids trace evidence modus operandi or MO that distinct pattern can be used to find similar crimes committed in an area.

expert witness vs non-expert witness can testify about...

expert:qualified based on their knowledge, skill, experience, training or education as such they can give an opinion to the court which is relevant to the tests performed. non:may also communicate their findings to the court without giving an opinion if they performed the analysis, but do not meet the criteria to be an expert witness.

what evidence linked to the car(the kid)

fibers, hairs, button paint, DNA

Positive result for Fast Blue

if a purple color develops within 1 min of adding Fast Blue the test is considered positive for semen

Forward spatter

is a fine mist /Blood which travels in the same direction as the source of energy or force which caused the spatter.

Immunogen

is a foreign substance that can cause antibody formation when introduced into a host

Epitope

is the portion of the immunogen that is recognized by the antibody. Each epitope can cause the production of its own antibody

Leucomalachite Green Assay

it is oxidized by the catalysis of heme to produce a Green color

Most commonly used blood group system is

ABO System

Affinity and Avidity

Affinity - the energy of the interaction of a single epitope on an antigen and a single binding site on a corresponding antibody. The bond strength depends on the specificity of the antibody for the antigen. 2) Avidity -the overall strength of the binding of the antibody to the antigen. It is basically the sum of the binding affinities of all the antigen-antibody binding sites. It also reflects the overall stability of an antigen-antibody complex.

fluroescence

An advantage of this testing and fluorescence testing is that the reagents can be sprayed over large areas to search for blood. • A positive reaction not only identifies blood, but can reveal patterns, such as shoe prints and blood spatter. • They are very sensitive, as such they can locate even small amounts of blood. • This makes them useful for crime scenes that have been cleaned and show no visible signs of blood!

More and less fluorescence

Saliva stains usually have a less intense fluorescence than that of semen stains.

Platelets

Small parts of the blood that cause clotting to stop bleeding, trap pathogens, and prevent additional pathogens from entering the body.

Class Characteristics

are a set of characteristics that allow a sample to be placed in a category with similar materials samples Properties of evidence that can be associated only with a group and never with a single source.

monoclomal antibodies

are made from only 1 cell type and reacts with a single epitope. • Monoclonal antibodies are specific, homogenous and can be obtained in unlimited quantities.

individual characteristics

are the unique characteristics of both evidence and references samples that share a common origin to a high degree of certainty. properties of evidence that can be attributed to a common source with an extremely high degree of certainty

impact spatter

(created when a force is applied to a liquid blood source) /A bloodstain pattern produced when an object makes forceful contact with a source of blood, projecting drops of blood outward from the source.

Back spatter

A bloodstain pattern resulting from blood drops that traveled in the opposite direction of external force applied; associated with an entrance created by a projectile, is larger and fewer drops./blood directed back toward the source of energy or force that caused the spatter

5 different types of search patterns

-Spiral investigators move in an inward spiral from the boundary center to the center of the scene or in an outward spiral from the center to the boundary of a scene. - Grid earches exhaustively through a manually specified subset of the hyperparameter space of the targeted algorithm. - Strip executed by the investigators beginning at one end of the search area and continuing forward in the same direction. - Quadrant A search method in which the crime scene is divided into smaller sections (zones or quadrants) and team members are assigned to search - zone breaks the crime scene area into squares. For example, a living room can be divided into four equal sections and examined by an individual

Expirated spatter

A bloodstain pattern resulting from blood forced by airflow out of the nose, mouth, or a wound/caused by blood from an internal injury mixing with air from the lungs being expelled through the nose, mouth or an injury to the airways or lungs.

two phases of bloodstain pattern analysis

1. Pattern Analysis - looks at the physical characteristics of the stain patterns including size, shape, distribution, overall appearance, location and surface texture where the stains are found. Analysts interpret what pattern types are present and what mechanisms may have caused them. • 2. Reconstruction - uses the analysis data to put contextual explanations to the stain patterns: What type of crime has occurred? Where is the person bleeding from? Did the stain patterns come from the victim or someone else? Are there other scene factors (e.g. emergency medical intervention, first responder activities) that affected the stain patterns?

How much saliva is produced per day

1.0 to 1.5 liters

How many loci does CODIS require?

13

How many stages modern forensic biology was developed in

3 1) Antigen polymorphism 2) Protein polymorphism 3) DNA Polymorphism

Complete antibodies vs incomplete antibodies

A complete antibody can perform both primary and secondary reactions that result in agglutination. An incomplete antibody can only perform initial binding and fails to form actual agglutination.

Presumptive tests

A positive result means that the presence of blood is possible, but the assays are not specific only for blood so other substances can give positive results./A negative result however means that blood is not present./are fast, sensitive and easy to perform. Since they are not specific though they should only be used as screening tools/Positive results should be followed up with more specific (confirmatory) testing methods.

BPA range encompasses

BPA can range from investigation and analysis of bloodstain patterns at the crime scene to bench work in the laboratory analyzing and DNA profiling the blood. Limited analysis can also be done using only photographs of the scene

red blood cells

Blood cells that carry oxygen from the lungs to the body cells.

white blood cells

Blood cells that perform the function of destroying disease-causing microorganisms

What type of of bodily fluids can be found at a crime scene

Blood, semen, sweat, saliva, vaginal secretions, urine, fecal, vomit

Blood Pattern Analysis use

Bloodstain analysts use established scientific methods to examine bloodstain evidence at a crime scene including information gathering, observation, documentation, analysis, evaluation, conclusion and technical (or peer) review.

impact the shape of a blood stain

By measuring the width and length of the stain, the angle of impact can be calculated, helping investigators determine the actions that may have taken place at the scene. As the angle of impact changes, so does the appearance of the resulting stain.

The most common staining technique for sperm

Christmas tree stain

Alec Jeffreys

Developed techniques for genetic fingerprinting and DNA profiling. He developed a revolutionary technique using VNTR

Karl Landsteiner

Discovered that blood can be grouped into different types, A, B, AB and O.

4 types of PPE

Disposable coverall body suits- Face masks - Safety eye glasses or goggles- Disposable gloves- Disposable shoe covers- Disposable hair net/Head protection Hearing protection Foot protection Eye protection

common methods for documenting crime scenes

Drawing sketches -starts with a rough sketch that will later be made into a finished work showing positions of people and objects to scale- Taking photographs -should include scales such as a ruler or other marker for accuracy of the size reference later. Should also have a log to note order of photos taken and any other info that might be important at a later date- Taking videos -should use scales as needed and also have a written log to note and relevant info while filming

special conditions for packaging evidence/different sources/if can be folded

Evidence from different sources -items of evidence should NOT be grouped in 1 package due to the possibility for evidence transfer from different sources. The exception to this rule is if all the items were found together then they can be put in a single container Folding of Evidence -folding of clothing, especially wet clothing, can transfer evidence from one part to another. An item must be dry before folding, a piece of clean paper must be placed between the different parts or layers so that they do not come in direct contact Packaging Materials -The best items will be made of paper such as bags, boxes and envelopes. Plastic bags or containers can be used in some cases, but are not acceptable for all evidence such as dried bloodstained evidence Liquid Evidence -tubes containing liquid should not be frozen since liquids expand in freezing temps and that expansion could lead to cracking. Tubes should be placed in their own plastic bags to prevent leaks and cross-contamination. It should be submitted to a lab ASAP.

What makes semen fluoresce

Flavin is the substance that causes semen to fluoresce under UV light which is why it is used when searching for semen stain evidence.

Plasma

Fluid portion of blood

Label sperm cell

Head The middle The tail

Blunt force injury

Objects inflicting this type of injury are usually larger, such as a bat or hammer./ mechanical injury to body resulting in tearing, shearing, or crushing; most common injury seen in healthcare, caused by blows or impact, MVA, and falls

most important reason to use BPA

One of the most important functions of bloodstain pattern analysis is to support or corroborate witness statements and laboratory and post-mortem findings.

Cross-reaction

When antibodies bind with lower strength to antigens that are similar in structure to an immunogen

Sharp force injury

These injuries are caused by an object with a relatively small surface area, such as an ice pick or a knife./occur from weapons with sharp edges, such as knives or blades

How to determine what blood type a child could have

This inheritance follows normal Mendelian principles. • Due to this inheritance pattern, blood type can be used to help determine paternity.

Multiple Analysis of Evidence

an item of evidence is going to have to undergo more than 1 type of testing the non-destructive test should be performed first. For example, collecting a bloody shoeprint should be done before any part of the print is collected for DNA testing

How to sign chain of custody/when it needs to be signed

Whenever evidence is handled or transferred, a custody form should be filled out and placed in the chain of custody document. • Each person who takes custody of an item MUST sign a chain of custody log. • The chain of custody keeps record of everyone who touched the evidence and helps prevent tampering or contamination. • An incomplete chain of custody could be used to make an item of evidence inadmissible in court due to the potential for unknown contamination or tampering.

Blood Pattern Analysis questions

Where did the blood come from? - What caused the wounds? - From what direction was the victim wounded? - How were the victim(s) and perpetrator(s) positioned? - What movements were made after the bloodshed? - How many potential perpetrators were present? - Does the bloodstain evidence support or refute witness statements? What occurred? - Where did the events occur? - Approximately when and in what sequence? - Who was there? Where were they in relation to each other? - What did not occur?

confirmatory test

a test that specifically identifies one substance

Evidence markers

accuracy of the size reference later./help to document the relative positions of evidence items in the crime scene.

ABO in investigations

blood typing is useful in criminal investigations because it allows you to narrow the suspect field based on the 4 blood types. • It is more useful for excluding suspects than including them because there is a high probability that any 2 randomly selected people could have the same blood type, but if the type at the scene is A and your suspect is B, you know that sample didn't come from them.

Oxidants

can cause false positive results by catalyzing the oxidation reaction even without any heme. Bleach and other household cleaners are examples of oxidants.

vasectomy affect semen

can still produce ejaculate, it will just contain only seminal vesicle and prostatic fluid. It will NOT contain any sperm cells.

Projection spatter

caused by arterial spurting, expirated spray or spatter cast off an object

Type of evidence should get the highest priority

corpus delicti

Void patterns

created when an object blocks the deposition of blood spatter onto a target surface or object and the spatter is deposited onto the object or person instead

The role of the 1st responder

should evacuate all living people from the scene and only authorized personnel should be allowed to enter the scene with proper documentation on the log sheet. • Suspects should be detained and questioned• Witnesses should be questioned • If a victim is injured the 1st responder should call for EMS. • All of this should be done as carefully as possible to not disturb the scene and notes should be made if any disturbance to evidence has occurred.

Amylose

simplest form of starch. consists of long, unbranched chains of glucose residues. It reacts strongly with iodine to form a dark blue color and amylopectin turns reddish-purple

what helped convict the police

so few models of the car, able to trace it back, they all told on each other or rolled on

Postzone

the amount of antigen is in excess so each antibody is saturated with antigen and cross-linking can not occur so no precipitate is formed

Prozone

the antibody is in excess so each antigen molecule is saturated with antibody, preventing cross-linking and no precipitate is formed

Zone of equivalence

the maximum level of precipitation occurs in this zone. As the concentration of antigen increases, the amount of precipitate increases since the ratio of antigen to antibody is optimal, cross-linking occurs