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Solving the Crime

Manual on how a CSI Investigates a Crime Scene

Ashley Aguasin

on 20 June 2011

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Transcript of Solving the Crime

Solving the Crime Bloodstains Tool Mark Evidence Shoe Print Evidence Forensic Entomology The Fire Basics Tire Track Evidence fingerprints Hair and Fiber Evidence Bite Mark Evidence Bloodstain Pattern Analysis So, basically there are 3 types of blood "patterns"

Passive Bloodstains
-patterns created from the force of gravity.
-drop, series of drops, flow patterns, blood pool, etc.

Projected Bloodstains
-patterns that occur when a force is applied to the source of the blood
-it also includes low, medium and high impact spatters

Transfer or Contact Bloodstain
-patterns created when wet, bloody objects come in contact with target surface
-wipe or swipe patterns from an object leaving a bloodstain The Bloodstains Release Height on Blood Droplets
- the higher the drop falls, the larger thae diameter of the droplet.
- as release height increases, drops get more spines and sattelite
- size change is not very noticeable before 120cm Impact Surface on Diameter and Shape of Bloodstain
- rough surfaces and uneven surfaces have spines
- obsorbent surfaces = smaller droplets with less splatter
- smooth surfaces = rough drops, which are easyest to analize How Can Blood be Evidence in a Crime? -Blood samples
-Blood droplets
-Blood spatter Certain defects or patterns may be left on a tool when it is made or used.
these specific details put on the tools can be used as evidence to link tools at the crime scene, to tools at a suspects home. Features to Analyze when dealing with Tool Mark Evidence -Defects such as nicks or chips
-Ridges or striation pattrens
-Paint chips or metal shards left on tool Investigtors can analyze a shoe to determine its "class" or type of brand name. specialist will look for individual characteristics, such as specific damages or wear patterns. Depending on the quality of the impression, they can identify an estimate of the size of this suspect, anlong with the speed at which they would be wlking or running. Featues to analyze when dealing with Shoe Print Evidence -Wear patterns caused by the way a person walks.
-Material defects or damage
-Tread patterns such as size and depth What do they do? A Forensic entomologist apply thier knowledge of entomology to provide information from criminal investigations. -identification of insects at various stages
-testifying in court to explain insect-related evidence
-determining an estimate for a postmortem interval or "PMI"
-collection and preservation of insects as evidence Specific Jobs The Life Cycle 1)Egg
2)First stage larva
3)Second stage larva
4)Thrid stage larva
6)Adult Terms to know, when Dealing with Fire. The Fire Triangle- Which shows the 3 elements needed o produce and sustain a fire.

The Flash Point- Is the lowest temperture that a substance must be heated in order for the fire to actaully burn.

The Point of Origin- The location in which the fire was started/the source.

The Burn Patterns- Noticeable patterns created by the fire as it burns.

Accelerants- Substances that encourage the fire to grow or "accelerate" the burning process.

Arson- A fire started deliberately. The Fire Triangle: Fuel- can be combustable material in any state of matter. (solid, liquid, gas)
Heat- the necessary enegry to increase the temperture of the fuel.
Oxygen- Fire requires an atmosphere with at least 16% oxygen. Point of Origin Char patterns- created by very hot fires that burn very quickly and move fast along its path:

-char patterns on a door will help an invesigator determine which side of the door the fire was on.
-char patterns on the floor will help an investigator determine the use of an accelerant and its path V-Patterns- fire burns up, in V-shaped patterns, so a fire that starts at an outlet agaisnt a wall.

- a very narrow V-shape might indicate a fire that was hotter than normal
- a wide V-shape might indicate a fire that was slow burning
- V-shapes could indicate that there was a "pool or orgin" rather than a "point" of orgin. Heat Shadows- occur when heavy furniture shields a part of the wall; can help determine the point of origin. Glass- glass fragments can also provide clues to a fire.

- light bulbs tend to burn toward the heat source
- shatters or cracks in glass of the windows can provide indications as to how the fire burned
- a dark layer on the glass could indicate a slow, smoldering fire
- clear glass with an abnormal pattern of cracking may imply a very hot fire To solve a crime of fire or arson, what would an investigator manage a fire scence? *hypothesize the reaosns for a the fire
*determine the heat source
*collect evidence
*document with notes, photographs and videos
*interview witness' Tire tracks are always important for investegations and are usually found in road accident scences.Tracks help investegators identify the type of vehicle that left the track. Processes such as ink prints of a tire, plaster casts or the track and photographs that can later be proven to match. Featues to Analyze when dealing with Tire Track Evidence *Tread patterns
*Width and depth of tread patterns
*Unique characterisitcs due to wear patterns of defects Arch Loop Whorl
(5%) (60%) (35%) Fingerprint Classes
There are 3 classes for all fingerprints the simplest type of fingerprints that are formed by ridges that enter one side of the print and exit on the other. No deltas are present 2 tpyes of Arches
-Plain Arch: ridges enter on one side and exit on the other side
-Tented Arch: similar to "plain" but has a spike in the center must have one delta and one or more ridges that enter and leave on the same side. 3 types of Loops
-Radial Loop: loops open toward the thumb or radius bone on the right hand.
-Ulnar Loop: loops opens toward the little finger or ulna bone on the right hand.
-Double Loop: whorls are made up of any two loops combined into one print. have atleast one ridge that makes a complete circuit. Have atleast 2 deltas. there are technically 3 types of whorls. 2 by poistion and one by visual differnce.
-Plain Whorls.
-Central Pocket Whorls.
-Accidental whorl: contain 2 or more patterns, or does not clearly fall under any of the other categories. The Science of Ridges Ridgeology: the study of the uniqueness of friction ridge stuctures and thier use for personal indenification Matching unique fibers on the clothing of a victim to fibers on a suspects clothing can he extremely helpful to an investigation, whereas the matching of common fibers sucha as white cotton and blue denim fibers would be less helpful to the investigation. The descovery
of cross transfers
and multiple
fiber transfers
between the
suspect's clothing and the victims clothing dramatically increases the likelihood that these 2 individuals had physical contact. There are 2 types of fabric though. Synthetic Fibers:
*more than half of all fibers used in production of textile materials are synthetic Natural Fibers:

*many natural fibers that come from plants or animals are used in the production of fabric.
*cotton fibers are the plant fibers most commonly used in textile materials.
*wool is the most frequently animal fiber used in production of natural fabric. Hair is produced from a structure called the hair follicle. Humans develop hair follicles during fetal development and no new follicles are produced after birth. Hair shape (round
or oval) and texture (curly or straight) is influenced heavily by genes. The physical appearence of hair can be affected by nutritional status and intentional alteration. The body area which includes the head, arm, leg, back and other parts of the body that hair originate from can be determined by the samples length, shape, size, and other physical characteristics. In order to test these hair folicles for DNA the "root" must be present. A Strand of Hair The Cuticle varies in its scales and thickness, and whether or not is contains pigment
The Cortex varies in thickness, texture and colour
The Medulla may very in thickness, continuity and opacity Like the cuticle, the medulla can be important for distingusihing hair of differnt species, but often does not lend much important information to the differentiation between hairs from differnt people Investegators can analyze bite marks for charcateristics to help them identify vitcims or suspects as well as exclude others. Marks can be left on a victims skin or other objects such as styrofoam cup, gum, or other impertional foods. Saliva or blood may be lefct behind, that can be tested for DNA. Dental records including X-rays can also provide useful information, especially when attepmting to identify a victim Types of Teeth *8 incisors
*Flat teeth at front
*Used for biting and some tearing/cutting *4 canines
*Pointy, single cusps
*used for ripping and tearing *8 premolars
*2 main biscuspids
*used for crushing food *8 molars
*wide flat teeth used for grinding food So there you have it. Ways to solve a crime. Throughout this Science and Tech class, i have learn alot about forensics and how a lot of the crime world works. There are always ways to catch a criminal, you just need to know where to look. Although most of you will might not continue a career in the criminal world, atleast you still know the basics of a crime. Whether is be looking at Impression Evidence or other types of evidence such as Fire, Blood or Entomology you now know it all. And now that you have you head wraped around how to slove a crime, this should take your mind off it.

Please watch Mrs. P :)
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