unit 7: crime scene and physical evidence crime scene : anywhere evidence may be located that will...
TRANSCRIPT
Unit 7: Crime Scene and Physical Evidence
Crime scene : anywhere evidence may be located that will explain events,
it may be one location or several locations.
Chapter 3
CORPUS DELICTI“Body of the Crime”
You must prove that a crime occurred that the person charged with the crime was responsible for the crime
Top Reasons for Committing a Crime Money Revenge Emotion—love, hate, anger
Source of Evidence Body Primary and/or Secondary Crime Scene Suspect(s)
Chapter 3
CRIME SCENE TEAM
A group of professional investigators, each trained in a variety of special disciplines.
Team Members First Police Officer on the scene Medics (if necessary) Investigator(s) Medical Examiner (if necessary) Photographer and/or Field Evidence Technician Lab Experts
Chapter 3
CRIME SCENE INVESTIGATION
Based on the scientific method and the Locard Exchange Principle, logic and forensic techniques
Involves: Recognition—scene survey, documentation, collection Identification—comparison testing Individualization—evaluation and interpretation Reconstruction—reporting and presenting
LEGAL CONSIDERATIONS
• One of the fastest ways for an investigator to lose friends at the crime lab is to collect the evidence improperly.
• There is nothing worse for a forensic scientist than to painstakingly go through mountains of trace evidence, spend hundreds of hours identifying and comparing pieces that prove the suspect guilty, and then have the whole thing thrown out of court because the evidence was collected improperly at the crime scene.
• The Fourth Amendment of the U.S. Constitution protects us against unreasonable search of our houses and seizure of our property.
• The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particu larly describing the place to be searched, and the persons or things to be seized.
• The courts go a long way in admitting physical evidence into a case.
• Physical evidence cannot be bribed, it cannot suffer a loss of memory, and it cannot see things from a biased perspective.
• Physical evidence is available to both the prosecution and the defense.
search warrant.
• Investigator must first obtain a search warrant.
• The search warrant must be obtained from a judge, and the investigator must give a good reason (probable cause) why they believe the evidence is present.
• The warrant must specify the location to be searched and what is to be seized.
search warrant.
• To obtain a search warrant a police officer must show:
• 1. probable cause
• The person or thing to be seized
• The place to be searched
There are four common exceptions that
allow a warrantless search and seizure.
• 1. Emergency. For example, the police are responding to a phone call by a neighbor about a domestic disturbance. They are standing outside the door of an apartment, and they hear gun shots and someone calling for help.
• 2. Prevent destruction of evidence: A fire department does not need a warrant to enter a burning building to put out a fire.
• The courts recognize that the chemicals (accelerants) used to start a fire quickly evaporate and that during the time required to obtain a search warrant the evidence may disappear or be destroyed
• 3. Consent: Once consent is given, an officer can conduct a search as if a warrant had been obtained. It is important to document the consent in some way, such as a written releasesigned by the suspect.
• 4. Pursuant to a lawful arrest: When an arrest is made, a policeofficer is allowed to search the person and their immediate surroundings.
• The definition of immediate surroundings is somewhat vague and is the center of much legal debate.
There are five basic steps that an investigator must follow at any crime scene:
1. Obtain a search warrant.
2. Secure and protect the scene.
3. Search the scene.
4. Document and record the scene.
5. Collect and package the evidence.
6. Submit the evidence to the crime lab
One of the most important duties of the first responding officer is to secure and protect the crime scene
PROCESSING ACRIME SCENE
Isolate and secure the scene
Document the scene Search for evidence Collect and package
evidence, maintaining the chain of custody
Submit evidence to the crime lab
FIRST OFFICERON THE SCENE
• A Assess the crime scene and assist those hurt
• D Detain the witness
• A Arrest the perpetrator
• P Protect the crime scene
• T Take notes
CRIME SCENE SURVEY
Walk-through—performed by the crime scene investigator, the first officer and sometimes the lead detective
Purpose: Mentally prepare a reconstruction theory Note any transient or conditional evidence that could change over time. Note weather conditions Note points of entry or exit, as well as paths of travel within the crime
scene Record initial observations of who, what, where, when, and how Identify special needs within the crime scene for personnel, precautions
or equipment and notify superior officers or other agencies
DOCUMENTATION
Notes—date and time, description of the location, weather and environmental conditions, description of the crime, location of the evidence relative to other key points, the names of all people involved, modifications that have occurred and other relevant information
Photography—photos of scene and surroundings, mid-range to close-up photos with various angles of each piece of evidence, photos as viewed by any witnesses.
Sketches—inclusion of date, time, scale, reference points, distance measurements, names of investigators, victims, suspects, and a legend (key)
Videography—allows narration (non-subjective) to be included
O.J. Simpson case,
• In the O.J. Simpson case, many of the investigators wandered through the crime scene without protective clothing and brought questions of contamination into the trial thus throwing out the evidence.
SEARCH PATTERNS
• The crime scene should be searched in a systematic fashion..
• The four standard search patterns used are strip, grid, spiral, and quadrant.
• The actual pattern used varies, and the shape and size of the crime scene can influence the choice, as the number of search personnel and the preferences of the lead investigator.
search patterns
• 1. spiral search• is well suited to round
crime scenes,. • . A single investigator
at an outdoor crime scene often uses the spiral search pattern.
• It has also been employed in underwater searches.
• strip or lane search • while a strip or lane
search is well suited to large areas when there are multiple searchers
search patterns
• A grid search • is similar to a strip
search but after completing the search in one direction, say east to west, the search is then done at a 90° angle, say south to north.
• A grid search takes longer to conduct but has the benefit of double-checking the area
• quadrant or sector search
• Can be applied to small or large crime scenes.
CRIME SCENE SKETCH
Date: August 14, 2005 Criminalist: Ann WilsonTime: 11:35 am Location: 4358 Rockledge Dr, St. Louis, Mo.
N
RECORDING THE SCENE
• The crime scene must be documented in the investigator's field notes as well as in a sketch.
• There must also be a visual record of the crime scene consisting of photographs.
• While there has never been a case of a crime scene being over documented, there have been many cases where vital clues have been overlooked, lost, or misplaced.
COLLECTING AND PACKAGING EVIDENCE
One individual should be designated as the evidence collector to ensure that the evidence is collected, packaged, marked, sealed, and preserved in a consistent manner
Each item must be placed in a separate container, sealed, and labeled
Most fragile is collected and packaged first Different types of evidence require specific or special
collection and packaging techniques The body is the property of the coroner or medical
examiner. The collection of evidence on the body is done by that department
PACKAGING
Most items should be packaged in a primary container and then placed inside a secondary one. These are then placed inside other containers such as paper bags, plastic bags, canisters, packets and envelopes depending on the type and size of the evidence.
• The preferred manner of recording a crime scene starts with a camera..
• While digital pictures are fast and easy to print, they are also easy to digitally alter and these alterations can be difficult to detect.
• For this reason it is important to make digital pictures as reliable as possible… or use film
• Photographs should be taken of everything that could be a potential piece of evidence.
• The crime scene can also be videotaped.
COLLECTION AND PROPER PACKAGING OF PHYSICAL EVIDENCE
• It is extremely important that evidence be collected properly or all its value may be lost.
• investigator should never directly come in contact with the evidence
• At a minimum, evidence can be collected using forceps or gloves and must never be directly touched by the investigator.
• For the purpose of packaging, evidence can generally be separated into four main categories, trace, nonbiological, biological, and arson, with general guidelines for each.
• Any unknown or questioned evidence is collected from a crime scene
• Most types of evidence can be sent via U.S. mail except explosives
Glass evidence
• Glass evidence is packaged in a rigid container so that it does not cut investigator
Blood soaked clothing
• should be air dried before wrapping and should be packaged in paper bags…this prevents molding
Soot from arson
• Soot from arson should be placed in a metal can.
• In the absences of any other container investigators can use druggist fold
• One of the most common mistakes made in collecting evidence is forgetting to collect a control
• One of the most common mistakes made by new investigators when collecting evidence is forgetting to collect controls ( similar type evidence collected away from the area of the crime)
• In the O.J. Simpson case many of the investigators walked through the original crime scene without wearing protective clothing (hair nets, latex gloves, shoe coverings, and so on) that would keep them from contaminating the scene.
• On June 12, 1994, the bodies of Nicole Brown Simpson and Ronald Goldman were found mur dered outside Nicole Simpson's home.
• Photographs of the crime scene actually show the investigators walking through the area and scattering vital evidence, such as blood.
• Worse yet, some of the investigators then went to the next investigation site, the home of O. J. Simpson, and tracked evidence from the initial crime scene along with them.
PHYSICAL EVIDENCE
• While almost anything can be physical evidence, it is sometimes helpful to break evidence down into categories:
• body fluids: blood, saliva, sweat, and semen• Explosives and incendiaries (arson) : chemicals used to start fires• Fabrics• Illegal drugs: narcotics, stimulants, ect…• Firearms• Glass: fragments and bullet holes• Soil:• Hair:• Fingerprints• Impressions: shoe tire, teeth• Paint• Liquids: biological and hazardous• Metals: poisonous, fragments• Questioned documents• Computer crime• DNA: blood, semen, saliva, body tissues, and hair
INDIVIDUAL CHARACTERISTIC EVIDENCE:
• Physical evidence is normally classified as either individual characteristic or class characteristic evidence.
• Individual characteristic evidence : physical evidence that can be associated with a single, unique source with a high degree of probability. Ex. Fingerprints, DNA, striations on bullet, paint chips
• Class characteristic evidence: Physical evidence that can be associated with a group. Ex blood type
Evidence Characteristics Class—common to a group of objects or persons ( most
evidence analyzed in a crime lab fits here)
Individual—can be identified with a particular person or a single source ( if the probability is low enough, class evidence can become individual evidence)
Blood DNA TypingFingerprints
Class vs Individual Evidence
Which examples do you think could be individual evidence?
Class vs Individual Evidence
The large piece of glass fits to the bottle—it is individual evidence
These fibers are class evidence—there are millions like them.
Class characteristic evidence • Human blood can be one of four different blood groups A, O, B, or AB.
• EXAMPLE: LETS say a victim is found dead in his apartment and that he has type A blood.
• There is evidence of a struggle, and scrapings from under his fingernails show traces of skin cells and blood.
• The blood is typed and found to be type O. • A suspect is arrested, and he also has type O blood. • How strong a piece of evidence is the blood type? • The percentages of the types of blood are well
known for various populations, and in the United States are as follows.
Solution
• Blood type: A B O AB
• Percentage: 40% 11% 45% 4%• If the murder occurred in New York City, with a
population of about 8 million, there are about 3.6 million people with type O blood.
• The number of people with this blood type can be calculated by the following formula.
• Number with trait = total number x percentage with trait/100• = 8,000,000 x %> = 3,600,000
• This is a very large group and, like many types of class characteris tic evidence, does not really make a very strong connection between the murder and the defendant.
• Blood type: A+ A- B+ B- O+ O- AB+ AB-• Percentage: 34% 6% 9% 2% 38% 7% 3% 1%
• If the blood found under the victim's nails is O+ and the defen dant is also O+, this means that there are 3,040,000 people in the Big Apple with the same blood type—still not a very convincing piece of evidence..
Second Example
• Let's say a similar murder in the small upstate town of Smithville Flats (population 399).
• In addition, this time the blood type found under the victim's fingernails is AB-and the chief suspect is AB-.
• The number of people in Smithville Flats with blood type AB- can be calculated as
• Probability = 399 x 1/100 = 3.99• This means there are probably four people in
the town with this blood type. This evidence would be more persuasive in convincing a jury that the suspect is the murderer
SUBMISSION OF EVIDENCE AND CHAIN OF CUSTODY:
• Once evidence is submitted to court, it is no longer a concern of the police department.
• However from the time the first officer responds to the crime scene until the evidence is delivered to the court, it is the responsibility of the police.
A chain of custody
• A chain of custody is a document that records the date, time, and person who has possession of the evidence from the time it is collected at the crime scene to the time it is turned over to the court.
• Any break in the chain of custody or period of time when the evidence was not secured is grounds to have the evidence thrown out of court.
• In general, the investigator of a suspected arson scene has 3 main avenues of investigation:
1. Modus operandi (mode of operation
2. Owner of building
3. Revenge
CRIME SCENE RECONSTRUCTION
• The crime lab is sometimes asked to reconstruct a crime scene from the physical evidence collected.
• Examples include the reconstruc tion of automobile accidents from skid marks and the physical damage to the cars and surroundings
TYPES OF PHYSICAL EVIDENCE
• Anything that is composed of matter and can be used to determine what happened in a crime is physical evidence.
• While almost anything can be physical evidence, we will concentrate on the most common types of physical evidence that are used in crime scene investigations
Arson
• While there are literally millions of different chemical reactions, chemist tend to combine them into three or four groups to make them easier to understand.
• One system groups chemical reactions into three major classes: precipitation, acid-base, and oxidation-reduction.
• Fire is an example of an oxidation –reduction reaction
• In an oxidation-reduction reaction there is a transfer of electrons from one chemical, called the reducing agent to another chemical, called the oxidizing agent
ARSON:
• 60F is temperature gasoline freezes
• 2% mixture of gasoline vapor in air is considered lean
• In a combustion reaction , isooctane is a fuel
• Chemical used to start a fire is called an accelerant
• For a combustion rxn to occur, the temperature must be raised to what is known as the ignition temperature ( gasoline is 536F)
• The fire keeps going until it runs out of the reducing agent or the oxidizing agent ( this is the limiting factor)
Ignition temp of some common materials
• Gasoline 536F• kerosene 410 F• Turpentine 488F• Paper 842F• Wood 489F• Coal 750F
– The three things needed to keep a fire going are fuel, oxidizer, and heat ( called the fire triangle).
– Remove one and the fire will go out.– Another temperature that is important is the flash point
(temperature at which the fuel produces enough vapors to support combustion)
– The flash point is always much lower than the ignition temperature.( ex gasoline ignition temp 536F, flash point temp is -50F)
• Soot and debris collected from a suspected arson scene must be packaged in a metal can.
• The headspace GC (headspace gas chromatography) is used to determine the presence of an accelerant in soot and debris
• The use of vapor concentration makes the detection of accelerants about 100x more sensitive
ARSON IVESTIGATION
• In general, the investigator of a suspected arson scene has 3 main avenues of investigation:
1. Modus operandi (mode of operation
2. Owner of building
3. Revenge
• A fire investigation should center on the point of origin of the fire.
• Man investigators use a portable combustion meter ( called a sniffer) to determine the point of origin of the fire.
• The sniffer has a wand that draws air in with an
internal pump.
• Dogs being used as sniffers
EXPLOSIVES;
• The difference between fires and explosions is the speed at which the oxidation-reduction reaction occurs.
• Fires have a rate-controlling step which is the speed at which oxygen can reach the fuel.
• Explosives the fuel is intimately premixed with the oxidizer so the rxn is much faster..
• Explosives can be subdivided into:1. Low explosives ( pipe bombs, gas mixtures, black
powder, ) 2. High explosives ( nitroglycerin)
• Ammonium nitrate has replaced dynamite as a common blasting agent
• TNT is an example of a secondary explosive• Small devices added to explosives to allow
identification in post explosion investigations are called taggants
FABRICS:
• Fabrics are both a good source of fibers and excellent carriers of fiber evidence.
• In general, fibers found on a suspect tend to show contact that occurred within the last 24 hours.
• Fibers are divided into two main categories:
1. Natural ( form fur of anima’s silkworms, and plants ex wool, mohair, cotton, cashmere, linen, silk )
2. Manufactured: also called synthetic ex nylon, rayonpolyester acrylic, Kevlar
Transfers of Fibers
• 1. Primary: occurs when a fiber is transferred from a fabric directly onto a victims clothing (direct)
• 2. Secondary: transferred fibers on the clothing of a suspect transfer to the clothing of a victim (indirect)
Types of Fibers
Synthetic Rayon Nylon Acetate Acrylic Spandex Polyester
Natural Silk Cotton Wool Mohair Cashmere
Animal fibers and Plant fibers
1. wool: sheep
2. Mohair and cashmere: goats
3. Furs: mink, rabbit, beaver and muskrat
4. Silk: worm coccoon
5. Angora wool: angora goat
1. Cotton
2. Linen
Fiber Comparison
Can you tell the difference(s) between the cotton onthe left and the rayon on the right?
• An article of clothing collected from a victim and that of a suspect must be packaged separately
• When fibers are collected in the victims mouth, investigators should also call dental records
• Fiber evidence can be collected by: Brushing, vacuuming, adhesive tape
• To test dye in a particular fiber, it can be extracted and then tested using thermal decomposition testing
An example in which fiber evidence was used to solve a crime was in the Wayne Williams' murder trial.
– Between July 1979 and May 1981, twenty-nine children in the city of Atlanta, GA, were murdered.
– There were details of the murders that led the police to believe that all had been committed by one man.
– The cause of death was normally asphyxiation, and certain fibers were found on the bodies, linking them together..
– Some of the most important fibers included the following: yellow-green nylon fibers, violet acetate fibers, dog hairs, blue rayon fibers, and yellow nylon fibers.
– Many of these fibers were very unusual, and so it was thought that they would be very useful in linking a suspect to the vic tims and the crime scene
– The yellow-green nylon fibers had a tri angular cross section, and it could be determined that they had been manufactured for a carpet.
– Inquiries sent by the police to textile producers led to the discovery that the fiber was from the Wellman Corporation.
– It had been purchased by West Point Pepperell Corporation to manufacture Luxaire English Olive carpet.
–
– It is interesting to note that after the newspapers printed a story about the police's interest in fibers found on the bodies, all subsequent victims were discovered either nude or with their outer clothing missing, and many were dumped in a river.
– The murderer had obviously read the story and was trying to remove any evidence before disposing of the bodies.
– This illustrates the danger of disclosing the details of an ongoing investigation.
– The Atlanta police and the FBI conducted stakeouts at access points to the river, wooded areas, and other potential sites where a body could be disposed of.
– At 2 a.m. on May 22, 1981, a stakeout team heard a loud splash and noticed a car slowly driving across the James Jackson Parkway Bridge over the Chattahoochee River.
– The driver, Wayne Williams, was stopped, questioned, and allowed to proceed.
• Two days later the body of Nathaniel Carter was found in the Chat tahoochee River about 1 mile downstream from the James Jackson Parkway Bridge.
• The same yellow-green nylon carpet fibers were present on the body.
• When Wayne Williams' story did not check out, the police obtained a search warrant for his home and cars.
• When the investigators searched Wayne Williams' home, they discovered that the floors were covered with Luxaire English Olive carpet.
Filament Cross-Sections
• They also discovered dog hairs and other fibers in his home that matched those found on the victims. In addition, other fibers matched the carpeting in cars that Wayne Williams had access to.
• The probability of Luxaire English Olive carpet fiber being present at random in a residence in Atlanta was estimated to be 0.00013.
• There were 28 different types of fibers that were used to associate Wayne Williams, with the victims and the crime scene.
• However, Wayne Williams was only convicted of killing 2 of the 29 children
Testing for Identification
Microscopic observation
Burning—observation of how a fiber burns, the odor, color of flame, smoke and the appearance of the residue
Thermal decomposition—gently heating to break down the fiber to the basic monomers
Chemical tests—solubility and decomposition
Testing for Identification
Density—mass of object divided by the volume of the object
Refractive Index—measuring the bending of light as it passes from air into a solid or liquid
Fluorescence—used for comparing fibers as well as spotting fibers for collection
Dyes Components that make up dyes can be
separated and matched to an unknown.
There are more than 7000 different dye formulations.
Chromatography is used to separate dyes for comparative analysis.
The way a fabric accepts a particular dye may also be used to identify and compare samples.
Collection ofFiber Evidence
Bag clothing items individually in paper bags. Make sure that different items are not placed on the same surface before being bagged.
Make tape lifts of exposed skin areas of bodies and any inanimate objects
Removed fibers should be folded into a small sheet of paper and stored in a paper bag.
Fiber Evidence
Fiber evidence in court cases can be used to connect the suspect to the victim or to the crime scene. In the case of Wayne Williams, fibers weighed heavily on the outcome of the case. Williams was convicted in 1982 based on carpet fibers that were found in his home, car and on several murder victims.
Shroud of TurinShroud of Turin
The Shroud of Turin is a The Shroud of Turin is a piece of ancient linen cloth piece of ancient linen cloth that measures about 14 feet that measures about 14 feet long by 3 1/2 feet wide, and long by 3 1/2 feet wide, and on this cloth is a very faint on this cloth is a very faint imprint of a human being imprint of a human being who appears to have been who appears to have been crucified. crucified.
Legend has it that this Legend has it that this Shroud is actually the burial Shroud is actually the burial cloth of Jesus Christ. cloth of Jesus Christ.
The Shroud takes it's name The Shroud takes it's name from its present location from its present location which is in the Cathedral of which is in the Cathedral of John the Baptist in Turin Italy John the Baptist in Turin Italy
The Sudarium of Oviedo:The Sudarium of Oviedo:Its History and Relationship to the Shroud of Its History and Relationship to the Shroud of
TurinTurin
One of the relics held by the cathedral in the One of the relics held by the cathedral in the town of Oviedo, in the north of Spain, is a town of Oviedo, in the north of Spain, is a piece of cloth measuring approximately 84 x piece of cloth measuring approximately 84 x 53 cm. There is no image on this cloth.53 cm. There is no image on this cloth.
Only stains are visible to the naked eye, Only stains are visible to the naked eye, although more is visible under the although more is visible under the microscope. microscope.
The remarkable thing about this cloth is that The remarkable thing about this cloth is that both tradition and scientific studies claim that both tradition and scientific studies claim that the cloth was used to cover and clean the the cloth was used to cover and clean the face of Jesus after the crucifixion face of Jesus after the crucifixion
Analysis of the SudariumAnalysis of the Sudarium
The Sudarium of Oviedo:The Sudarium of Oviedo:
The first and most obvious coincidence is that the The first and most obvious coincidence is that the blood on both cloths belongs to the same group, blood on both cloths belongs to the same group, namely AB.namely AB.
The length of the nose through which the pleural The length of the nose through which the pleural oedema fluid came onto the sudarium has been oedema fluid came onto the sudarium has been calculated at eight centimetres, just over three inches. calculated at eight centimetres, just over three inches. This is exactly the same length as the nose on the This is exactly the same length as the nose on the image of the Shroud.image of the Shroud.
If the face of the image on the Shroud is placed over If the face of the image on the Shroud is placed over the stains on the sudarium, perhaps the most obvious the stains on the sudarium, perhaps the most obvious coincidence is the exact fit of the stains with the beard coincidence is the exact fit of the stains with the beard on the face. As the sudarium was used to clean the on the face. As the sudarium was used to clean the man's face, it appears that it was simply placed on the man's face, it appears that it was simply placed on the face to absorb all the blood, but not used in any kind face to absorb all the blood, but not used in any kind of wiping movement.of wiping movement.
The Sudarium of OviedoThe Sudarium of Oviedo
A small stain is also visible A small stain is also visible proceeding from the right hand side proceeding from the right hand side of the man's mouth. This stain is of the man's mouth. This stain is hardly visible on the Shroud, but Dr. hardly visible on the Shroud, but Dr. John Jackson, using the VP-8 and John Jackson, using the VP-8 and photo enhancements has confirmed photo enhancements has confirmed its presence.its presence.
The thorn wounds on the nape of the The thorn wounds on the nape of the neck also coincide perfectly with the neck also coincide perfectly with the bloodstains on the Shbloodstains on the Sh
FIREARMESFIREARMES
BULLET COMPARISON;BULLET COMPARISON; The forensic scientist has The forensic scientist has
several methods of analysis for several methods of analysis for any questioned bullet. any questioned bullet.
First step is an overall First step is an overall observation of the bullet observation of the bullet indicates its general indicates its general characteristics.characteristics.
Bullet Type Meaning PurposeBullet Type Meaning Purpose FMJ metal jacket deep penetration, FMJ metal jacket deep penetration, (military use)(military use) JHP jacketed hollow point controlled expansionJHP jacketed hollow point controlled expansion (accurate, hunting) (accurate, hunting) SJHP semijacketed hollow pt great expansionSJHP semijacketed hollow pt great expansion (accurate, hunting)(accurate, hunting) FMC full metal case light metal jacketFMC full metal case light metal jacket SP soft point greater penetration SP soft point greater penetration than hollow ptthan hollow pt WC wad cutter target practice WC wad cutter target practice ( leaves round hole in paper)( leaves round hole in paper) SWC semi-wad cutter target practice, general useSWC semi-wad cutter target practice, general use RN round nose general practiceRN round nose general practice
The diameter and total mass of the bullet The diameter and total mass of the bullet are also measured. are also measured.
The diameter indicates the caliber of the The diameter indicates the caliber of the bullet and type of weapon that fired it. bullet and type of weapon that fired it.
The mass of the bullet indicates the The mass of the bullet indicates the particular class of ammunition it belongs particular class of ammunition it belongs to.to.
The striation marks on the bullet are The striation marks on the bullet are examined next. examined next.
The number of lands and grooves are The number of lands and grooves are noted, along with the direction of twist. noted, along with the direction of twist. The rate of twist is also measured. The rate of twist is also measured.
The rate of twistThe rate of twist refers to the pitch or refers to the pitch or angle the striation marks make with the angle the striation marks make with the longitudinal axis of the bulletlongitudinal axis of the bullet
Rate of twist = Rate of twist = 150(diameter of 150(diameter of bullet )bullet )22
Length of bulletLength of bullet
EXAMPLE;EXAMPLE; A bullet with a diameter of A bullet with a diameter of 0.357 ( a 357 magnum handgun caliber) has 0.357 ( a 357 magnum handgun caliber) has a length of 1.000 inches. a length of 1.000 inches.
What is the optimum rate?What is the optimum rate?
Rate of twist = Rate of twist = 150 (0.37)150 (0.37)2 = 192 = 19 1.0001.000
This bullet would be expected to be fired from a gun This bullet would be expected to be fired from a gun with a rate of twist of 1 in 19 ( one complete twist of with a rate of twist of 1 in 19 ( one complete twist of the bullet for ever 19 in of travel) the bullet for ever 19 in of travel)
This formula can be useful in estimating the length This formula can be useful in estimating the length of a bullet that has been crushed on impactof a bullet that has been crushed on impact
A cartridge case can be matched to a gun A cartridge case can be matched to a gun by comparing extractor, ejector and firing by comparing extractor, ejector and firing pins.pins.
22 caliber gun does not leave GSR on 22 caliber gun does not leave GSR on shooters handshooters hand
Wound diameter is 1 inch wound per 1 yard Wound diameter is 1 inch wound per 1 yard of distanceof distance
The national Intergrated Ballistics The national Intergrated Ballistics Information Network (NIBIN) is the Information Network (NIBIN) is the system that allows forensic scientist system that allows forensic scientist to enter digitally captured images of to enter digitally captured images of fired bulletsfired bullets
GUNSHOT RESIDUEGUNSHOT RESIDUE (GSR) (GSR)
The presence of GSR on the victim can be The presence of GSR on the victim can be used to estimate the distance between the used to estimate the distance between the victim and the gun, which can be very victim and the gun, which can be very important in establishing whether the important in establishing whether the shooting was a case of suicide, self-defense, shooting was a case of suicide, self-defense, or murder. or murder.
Distances are described asDistances are described as : :1.1. contact, contact, 2.2. near contact, near contact, 3.3. intermediate contact. intermediate contact. Beyond 3ft, the distance is difficult to Beyond 3ft, the distance is difficult to
determine.determine.
contact shotcontact shot
A A contact shotcontact shot ( often seen in execution ( often seen in execution shootings or suicides) causes a star-shaped shootings or suicides) causes a star-shaped tear in any fabric, or skin over bone. tear in any fabric, or skin over bone.
A circular bruise normally develops over the A circular bruise normally develops over the skin as a result of the pressure of the skin as a result of the pressure of the gases. gases.
Burning of fabric or skin due to the heat of Burning of fabric or skin due to the heat of the expanding gases is also seen.the expanding gases is also seen.
near-contact shotnear-contact shot show show
A A near-contact shotnear-contact shot show a very heavy show a very heavy concentration of GSR and considerable concentration of GSR and considerable stippling ( presence of small abrasions stippling ( presence of small abrasions caused by unburned powder and small caused by unburned powder and small metal fragments striking the skin)metal fragments striking the skin)
intermediate shotintermediate shot
An An intermediate shotintermediate shot shows a wider, lighter shows a wider, lighter GSR pattern. GSR pattern.
The bullet hole also tends to be more The bullet hole also tends to be more irregular as the bullet begins to tumble in irregular as the bullet begins to tumble in flight. flight.
An entrance wound is always smaller and An entrance wound is always smaller and has inverted margins ( skin bent into the has inverted margins ( skin bent into the body) while an exit would is larger and has body) while an exit would is larger and has everted margins (skin bent outward)everted margins (skin bent outward)
There are two common test to There are two common test to determine if a person has recently fired determine if a person has recently fired
a weapon:a weapon: 1. atomic absorption spectroscopy (AAS).1. atomic absorption spectroscopy (AAS). When the gun is fired, some of the blast goes When the gun is fired, some of the blast goes
backward and covers the hand of the shooter. backward and covers the hand of the shooter. Lead, barium, and antimony would be very Lead, barium, and antimony would be very prominent on the shooters hands. prominent on the shooters hands.
The backs of the suspects hands are swabbed, The backs of the suspects hands are swabbed, and the swabs are introduced into the AAS.and the swabs are introduced into the AAS.
2. Scanning electron microscopes with an 2. Scanning electron microscopes with an energy dispersive x-ray attachment (SEM/EDX) energy dispersive x-ray attachment (SEM/EDX) one of the best methods for GSR determinationone of the best methods for GSR determination
QUESTIONED QUESTIONED DOCUMENTSDOCUMENTS
Any document whose source or authenticity Any document whose source or authenticity is uncertain is referred to as a questioned is uncertain is referred to as a questioned document.document.
Today more than 40% of all counterfeit U.S. Today more than 40% of all counterfeit U.S. currency is produced by digital printers, and currency is produced by digital printers, and is found abroad ( overseas)is found abroad ( overseas)
About 80% of U. S. counterfeit currency About 80% of U. S. counterfeit currency comes from Columbia ( the country, not the comes from Columbia ( the country, not the town).town).
The sample on the left is a The sample on the left is a copy of just one of the copy of just one of the letters sent by the serial letters sent by the serial murderer that called murderer that called himself Zodiac. himself Zodiac.
There are many samples There are many samples that were sent to that were sent to authorities over the years authorities over the years from the Zodiac and in at from the Zodiac and in at least two cases letters least two cases letters were received that proved were received that proved to be hoaxes through to be hoaxes through handwriting analysis.handwriting analysis.
SECURITY FEATURES SECURITY FEATURES AGAINST COUNTERFEITING:AGAINST COUNTERFEITING:
1.1. WatermakersWatermakers: formed by varying paper density. : formed by varying paper density. The area is visible if held to the light and The area is visible if held to the light and appears as darker and lighter areas.appears as darker and lighter areas.
2.2. Color shifting inksColor shifting inks: the ink appears green when : the ink appears green when viewed directly and changes to black when the viewed directly and changes to black when the note is tiltednote is tilted
3.3. Fine line printing patternsFine line printing patterns: found behind the : found behind the portrait on the front and around the historic portrait on the front and around the historic buildings on the backbuildings on the back
4.4. Enlarged off center portraitsEnlarged off center portraits5.5. Low vision features:Low vision features: 1996 $20, $50 and 1999$5, 1996 $20, $50 and 1999$5,
$10 have a large dark numeral on a light $10 have a large dark numeral on a light background on the lower right corner of the background on the lower right corner of the backback
6.6. Security threadSecurity thread: found on all 1990 series up : found on all 1990 series up except the $1except the $1
HANDWRITING ANALYSIS:HANDWRITING ANALYSIS:
Features such as the spacing of letters, Features such as the spacing of letters, angle, slant, pressure, shape and so on, angle, slant, pressure, shape and so on, help a handwriting expert to tell if 2 help a handwriting expert to tell if 2 samples were written by the same samples were written by the same individual. individual.
There are certain rules to follow when There are certain rules to follow when obtaining a handwriting sample from a obtaining a handwriting sample from a suspect (such as have the suspect in a suspect (such as have the suspect in a comfortable chair and give them a comfortable chair and give them a pen/pencil similar to that in question, pen/pencil similar to that in question, content should also be dictated so suspect content should also be dictated so suspect never sees document in question)never sees document in question)
COMPUTER CRIMECOMPUTER CRIME The drive may be damage, erased, or encrypted. The drive may be damage, erased, or encrypted.
Hard drives are made of multiple platters Hard drives are made of multiple platters containing a material that can be easily containing a material that can be easily magnetized ( an old trick is to put the hard drive magnetized ( an old trick is to put the hard drive in a freezer, the data can often be read while the in a freezer, the data can often be read while the platters are cold) . platters are cold) .
If the data has been erased, it is often still If the data has been erased, it is often still possible to recover all the files ( when a file is possible to recover all the files ( when a file is deleted, the only thing that is erased is the deleted, the only thing that is erased is the reference to the file save in a special location on reference to the file save in a special location on the hard drive) .the hard drive) .
There are various programs available for the There are various programs available for the recovery of deleted files. Windows has a way recovery of deleted files. Windows has a way for storing information about every web site for storing information about every web site you visit.you visit.
When an investigator comes upon a When an investigator comes upon a computer that may have valuable information computer that may have valuable information on it, it should never be shut down by clicking on it, it should never be shut down by clicking on the turn of computer icon. on the turn of computer icon.
Instead just pull the power cord out of the Instead just pull the power cord out of the wall. wall.
The computer can then be taken to the crime The computer can then be taken to the crime lab.lab.
DNA EVIDENCEDNA EVIDENCE
The DNA in every cell of your body is the The DNA in every cell of your body is the same. same.
The DNA sample collected from a crime scene The DNA sample collected from a crime scene must be compared to the DNA sample must be compared to the DNA sample obtained from the suspect.obtained from the suspect.
A point by point comparison is made, and if A point by point comparison is made, and if any of the features of the DNA from the any of the features of the DNA from the suspect do not match the crime scene DNA, it suspect do not match the crime scene DNA, it must be from another individual. must be from another individual.
DNA evidence can be used to both convict DNA evidence can be used to both convict the guilty and exonerate the innocent.the guilty and exonerate the innocent.
mitochondrial DNAmitochondrial DNA
Another source of DNA testing Another source of DNA testing involves mitochondrial DNAinvolves mitochondrial DNA
Mitochondria in your cells is an exact Mitochondria in your cells is an exact copy of the mitochondrial DNA in your copy of the mitochondrial DNA in your mothers cell. mothers cell.
This means that brothers and sisters This means that brothers and sisters all have the same mitochondrial DNA all have the same mitochondrial DNA and that all the children of sisters also and that all the children of sisters also have the same Mitochondrial DNA.have the same Mitochondrial DNA.
EXAMPLE:EXAMPLE:
Jessie James was rumored to have escaped Jessie James was rumored to have escaped the 1882 shooting attach by the 1882 shooting attach by
Bob Ford. Bob Ford. Did he really die or was someone else Did he really die or was someone else
buried in his grave. buried in his grave. Mitochondrial DNA was extracted from the Mitochondrial DNA was extracted from the
teeth of the body buried in James’s grave teeth of the body buried in James’s grave and was compared to a mitochondrial DNA and was compared to a mitochondrial DNA sample from a grandchild of Jesse James’s sample from a grandchild of Jesse James’s sister…they matched proving that the body sister…they matched proving that the body in the grave was that of Jesse James. The in the grave was that of Jesse James. The remains of Jesse Jamesremains of Jesse James
