ADMINISTRATION OF

JUSTICE 

 

FORENSIC SCIENCE 

 I. INTRODUCTION 

A. Forensic science is the application of scientific knowledge and technology to criminal and civil law enforcement as it pertains to the framework of our justice system.

 

1. Forensic science has two principle applications.

  a. First, is to supply accurate

and objective information that reflects the events that have occurred at a particular incident.

(1) This includes crimes against the person or property

 b. Second, forensic science monitors and

enforces compliance with existing legislation. This includes monitoring:

(1) food and water quality.   (2) the nature, potency and purity of pharmaceuticals.

(3) the production and release of industrial pollutants and motor vehicle emissions.

(4) the manufacture and use of agricultural - chemicals.

  B. Forensic science is the scientific

study that is specifically designed to assist the law enforcement community and the judicial system by applying science to the law.

 1. Forensic science uses highly

developed technologies to uncover scientific evidence in a variety of fields.

  2. Forensics helps in crime

detection and investigation by:  a. systematically examining

a crime scene.   b. identifying evidence at

the crime scene.

c. evaluating and interpreting of physical evidence found at the crime scene.

 C. When crimes are committed, the

person who commits the crime often leaves behind a record of himself or his actions in the form of physical evidence.

 

   1. Forensic science is most

commonly used to investigate criminal cases involving a victim, such as assault, robbery, kidnapping, rape, or murder.

  D. The forensic scientist makes use

of a wide spectrum of scientific knowledge and skills he/she has developed through formal education and on-the-job training.

1. A forensic scientist is called upon to examine a variety of exhibits since almost any material found at a crime scene may be potential physical evidence.

  2. Examination may be as simple as

matching pieces of broken glass found at the scene of a hit-and-run traffic accident.

  3. Examinations may involve the

use of very complex instruments of technology.

  a. For example, in the analysis

of a suspected cocaine sample or blood sample.

II. HISTORY OF FORENSIC SCIENCE   A. Combining the medical and legal

approach to investigating crimes currently practiced in the United States today originated in 12th

century England.

  1. King Richard I established the

Office of the Coroner.   a. Main duty was to maintain

a record of all criminal matters in the county.

b. Responsible for investigatingall deaths regardless of

whether it was the result of a suicide or homicide.

  2. Over time, the need for a more

scientific investigation of deaths became apparent.

  a. Coroners began calling

on physicians for help.

b. Medical schools began to prepare doctors for this added responsibility.

(1) 1807 - the University of Edinburgh in Scotland established the Department of Legal Medicine.

 B. The early British colonists

brought the coroner system with them to the America’s in the fifteenth century.

1. Coroners were appointed by

a representative of the crown to investigate violent and unexplained deaths.

  2. After the American Revolution

elected officials appointed coroners.

  a. As medical involvement in

the investigations of deaths increased, it became a requirement that investigators

have a specific academic background.

 b. 1877 – Massachusetts adopted a

statewide system called the Office of the Medical Examiner, to be headed by a physician.

c. 1915 - New York City established a medical examiner who was specifically authorized to investigate all:

  (1) deaths resulting from

criminal violence.

(2) accidental deaths and suicides.

(3) deaths that occurred suddenly to people who appeared to be in good physical health.

 

C. The field of forensic science today is one of high-technology using the most advanced and sophisticated equipment. Some examples of these modern

devices and techniques are:

  1. the electron microscope.

2. the use of lasers. 3. the use of ultraviolet and infrared light.

4. the use of advanced analytical chemical techniques.

5. the use of computerized databanks to analyze and research evidence. 

 

 III. FORENSIC SCIENCE AND THE

LEGAL SYSTEM 

A. Modern forensic science has a broad range of applications in our criminal justice system.

  1. It is used to settle issues

in civil cases such as fraud, forgery, or damages that are attributed to negligence.

  2. It can help law-enforcement

officials determine whether a law or regulation has been violated in:

  a. the marketing of foods

and drinks.

 b. the manufacture of medicines.

c. the use of pesticides on crops.

3. It can also determine whether

automobile emissions are within a permissible level and whether drinking water meets legal purity requirements.

 B. Medical examiners are requested to give

expert testimony in court proceedings on a regular basis.

  1. Expert testimony is information provided by a specialist who has been recognized by the court as having expert knowledge about evidence in the case.

 

a. Expert testimony is governed by different rules.

 2. The average citizen is considered an “ordinary” witness and their testimony is restricted to statements about what theyactually saw or heard.  

a. Ordinary witnesses may not state opinions about the facts of a case.

b. Ordinary witnesses may not quote statements made by other people to support their testimony.

3. The expert witness on the other

hand is allowed to express an opinion about the validity of the evidence and may quote the

statements of other experts that support their opinion.

 

  IV. THE MEDICAL EXAMINER 

A. The central figure in the forensic investigation of crimes involving a victim is the medical examiner.

  1. It is the medical examiner’s

responsibility to:  

a. go to the crime scene

b. conduct an autopsy of the body in cases of death

c. examine available medical evidence and appropriate laboratory reports

d. examine the victim's previous medical history

e. prepare a report for the district attorney outlining all pertinent information

B. Medical examiners are usually physicians who specialize in forensic pathology - the study of structural and functional changes in the body as a resulting from injury.

  1. Their training and qualifications

generally include having a medical degree and they have completed an apprenticeship in a medical examiner's office.

 V. FORENSIC SCIENTISTS  A. Within the field of forensic science

there are many areas in which forensic scientists chose to specialize. Some examples of those specialty areas are:

  1. anthropology: (the study

of human beings)

2. forensic biology: chemistry, and physics

  3. odontology: (the study of teeth)   4. pathology: (the examination of

body tissues and fluids)

  5. psychiatry: (the study of the human

mind)   6. forensic toxicology: (the study of

poisons, including drugs) 

7. toolmarks: (consists of striations or impressions left by tools on objects)

  8. documents: (relationships

between documents and inscription) 

9. firearms: (characteristics between firearm and projectile, projectile and target)

 10. forensic imaging: (image fraud

detection – image analysis)

  11. latent fingerprints: (processing

latent finger prints on evidence from crime scenes)

  12. microscopy: (pertaining to the use

of microscopes and microscopic evidence)

13. polygraph: (recording variations in the heartbeat and respiratory movements)

  B. Law enforcement agencies often

call upon forensic scientists who are specialists in these various fields for help in the investigation of a crime.

  1. Forensic anthropologists

determine the sex, height, weight, and ethnic group of a deceased person from an incomplete body.

  a. Marks on the bones often

indicate past injuries, diseases, and occupational stresses

suffered by the individual.

b. Investigators can identify a body by comparing old X-rays and the medical history of a missing person with the findings

of the forensic anthropologist.

 2. Forensic odontologist’s examine

and characterize the teeth of unidentified bodies when fingerprints or other

identification is not available.   a. Dental charts of missing

individuals can then be compared with the forensic

odontologist's report to help identify the body.

 3. Forensic pathology deals with

the postmortem investigation of sudden and unexpected death.

  a. Proximate cause of death.

The initial injury that led to a sequence of events which caused the death of the victim.

b. Immediate cause of death. The injury or disease that finally killed the individual.

 

  

4. Psychiatry, (the study of the human mind)

  a. Involves mental illness

and disorder.

b. Causes of mental illness and disorder.

c. The diagnosis and treatment of disorders.

d. May also be used in profiling.

(1) Investigators can examine certain evidence found at crime scenes to come up with a personality profile

of the offender.

 5. Whenever drugs or poisons

are involved in a crime, the investigating agency may obtain

the services of a toxicologist.   a. Toxicologists detect and

identify any drugs or poisons present in a person's bodyfluids, tissues, and organs.

b. This type of investigation is conducted on both the victim and, the suspected perpetrator of the crime when possible.

 VI. EXAMINING EVIDENCE  A. The medical expert investigates

many different types of violent crimes.

1. The medical examiner must try to determine whether a violent death was an accident, a suicide, or an unlawful homicide (murder).

  2. The medical examiner must

conduct an investigation of the crime scene and perform an autopsy to determine cause of death.

 B. Cases involving firearms.  1. In cases involving gunshot

wounds, the medical examiner will look for gunpowder residues that may be left on:

a. the clothing of the victim. b. the area around any

wounds on the victim.

2. This information will be used to

estimate how far away the gun was when the victim was shot.

  3. This may also help determine

whether the gun was fired by the victim or another person.

  C. Cases involving knives.

1. When knife wounds are involved, the medical examiner must

distinguish between a cut and a stab wound.   a. A cut is an injury that

is longer than it is deep.

b. A stab wound is an injury that is deeper than it is long.

  2. The examiner also looks for self-defense

wounds, cuts that are caused when an intended victim grabs the knife of an

assailant.  3. Cuts, are commonly involved with suicide.   a. There are usually numerous

superficial parallel cuts visible on the body.

b. These type of cuts indicate repeated attempts, before the individual was able

to make the final deep cut.   (1) These cuts are called

hesitation wounds.

(2) They indicate a suicide rather than a homicide.

  D. Investigations involving asphyxiation. 

1. Medical examiners are also called upon to

investigate cases of death from lack of oxygen in the blood.

  a. Asphyxiation may be the result of:

(1) hanging, which may be an accident, suicide, or a homicide that could be

lawful or unlawful.

(2) death by strangulation at the hands of another.

(3) obstruction of the victim's air passage by an object in the throat.

(4) suffocation caused by a gas such as in carbon monoxide poisoning.

  2. Deaths involving carbon

monoxide poisoning in a closed garage with no marks found on

the body usually indicate a suicide.

  a. The presence of tools

around the car and grease found on the victim's hands suggests an accidental death.

b. A wound caused by a blow to the head and the absence of carbon monoxide in the blood would indicate an attempt to make a homicide look as if it where a suicide.

  

 VII. TECHNIQUES OF FORENSIC SCIENCE 

A. Forensic science uses the most sophisticated laboratory equipment and techniques.

  1. Forensic technology is used to

detect the presence of substances in victims, suspected criminals, and at the crime scene.

  a. Alcohol breath-testing

instruments are so accurate that their results are capable

of providing evidence in court.

b. Gas chromatography permits detection of alcohol and other drugs, such asbarbiturates, cocaine, amphetamines, and heroin.

Ion Chromatography System

  2. When a body is discovered in a lake, or

river and the lungs are filled with water the medical examiner must determine if the drowning occurred where the body was found or at some other location.

 a. A microscope is used to look for

the presence or absence of diatoms, single-celled algae found in all natural bodies of water.

b. An absence of diatoms raises the possibility the drowning took place in a sink or bathtub since diatoms are filtered from household water.

 3. Microscopes that can magnify

objects 100,000 times are used to detect the minute gunpowder particles left on the hand of a person who has recently fired a gun. a. Chemical analysis of these particles can help identify their origin from a particular type of bullet.

 B. Forensic examination of substances found at the scene of a crime often establish the presence of the suspect

at the scene.

1. One of the oldest techniques

of forensic science is dusting the crime scene for fingerprints.

  a. In one method of obtaining a

fingerprint, a fine powder is spread over a surface with a brush or magnetic wand. 

(1) The powder sticks to

proteins secreted by the sweat glands on the skin ridges of the fingertips.

(2) When the excess powderis removed, an outline of the contours of the ridgesremains.

  2. Another method of obtaining a

fingerprint is to chemically treat the print to reveal the contours.

  a. Since no two fingerprints

are the same, fingerprinting provides a positive means

of identifying someone.

  3. Computer technology now allows

fingerprints to be recorded digitally and transmitted electronically for rapid identification.

 4. Other types of evidence often

found at a crime scene includes blood, hair, skin, or semen.

  a. Technology now allow

scientists to examine a persons (DNA), or genetic

material, to establish whether they belong to the victim or to a suspected assailant.

b. The use of DNA for such identification

purposes is commonly referred to as DNA fingerprinting.

  5. Human bite marks can also be

used as circumstantial evidence.

a. Bites may be found on the body of a homicide victim or other objects found at the crime scene.

b. Forensic scientists may fill impressions caused by human bites with liquid plastic.

 (1) The hardened cast formed

is a very accurate replica of the assailant's teeth.

(2) This replica can be comparedwith a cast made from the teeth of the suspect.

VIII. FIREARMS AND TOOLMARK IDENTIFICATION  

A. Firearms examination involves the identifying characteristics

between firearm and projectile, projectile and target.

Ballistics Microscope

  1. This generally includes matching bullets to the gun that is believed to have fired them.

  B. Toolmark identification involves

the identifying characteristics between tools, such as a pry bar, and objects such as a door frame it was used to pry open.

  C. Included in this category would

be explosives and imprint evidence.  

1. The majority of physical evidence collected concerns itself with two types of characteristics.

 a.   Class characteristics that

are common to a group of similar objects.

 (1) All Air Jordan sneakers

have the same shape and same tread design on the bottom.

 

  b. Individual characteristics are

unique to a given object and set it apart from similar objects. 

(1) Air Jordans worn over time cause the treads wear to down. They get little pits and gouges in them. 

(2) These little pits and gouges are individual to a specific shoe since no one has walked over the exact same surfaces in the exact same way in their Air Jordans.  

  D. The concepts of class and individual characteristics are most important in firearms examination.  

1. The purpose of the firearms examination is to match a bullet to the gun that fired it and exclude all others.

Test Fire for Comparison

  E. Bullet Matching.   1. Rifling gives the bullet a

signature marking that is unique to the weapon that fired it.

 

  a. Rifling is the result of the manufacturing

process of the firearm and serves to put spin on the bullet.

 

(1) Rifling improves accuracy.

Probably the most common method used today to rifle barrels is button rifling. Button rifling uses a different approach to forming the grooves in the barrel.  A button as seen above is a very hard steel plug that is forced down an unrifled barrel.

  2. Rifling consists of lands and

groves that spiral down the gun barrel.

  a. As the bullet passes down

the barrel, microscopic scratches from the lands

and grooves mark the bullet.  

b. These microscopic scratches are the result of the manufacturing process

and are totally unique to a particular firearm.

Valley

Hammer Forged 6-Right Polygonal Rifling Pattern

Hill

  3. Comparison tests are made in

the lab by test firing a bullet through the suspect weapon.  

  a. The test fired bullet is

then compared under a comparison microscope, side by side, to the bullet recovered from the crime scene.  

b. The bullets are rotated until the striations can be made to line up, showing a match.  

 (1) If the striations cannot

be lined up, the result is negative.

  F. Imprint Evidence.   1. There are two basic types of

imprint evidence.  a. Three dimensional impressions,

in which an object is pressed into something soft that will retain the impression of that object.

(1) Stepping into mud and leaving a shoe print would be an example.

  b. Two dimensional impressions,

in which objects transfer an image from one surface to another.

 (1) Paint coats the bottom of

the shoe when a person steps into spilled paint.

(2) It is then transferred to another surface when the person steps in an area free of paint.  

(3) When the shoe is removed from the paint the paint removed by the shoe creates a negative image of the bottom of the shoe in the paint spill.

  2. Impression evidence is not just

used for shoes, impression evidence can also be used with tire impressions and toolmarks.

  a. Wheel base may help to

narrow down the make of the car.

b. The tread design itself can narrow down the list of possible cars.

  (1) Individual tire wear

will show up in the impression.

  G. Toolmark Evidence (three types

of toolmark impressions). 1. Compression, in which a

tool surface presses into a softer material;

 

2. Sliding, in which a tool  (such as a knife) scrapes across a surface causing parallel striations;

  3. Cutting, which is a

combination of the above two types (such as a scissor cut).

  4. All three types can yield class

and individual characteristics.    a. Marks left on a window

frame from a pry bar can be matched back

to that specific pry bar.

  H. Explosives. 1. Explosives residue can be

analyzed to determine the type of explosive used in a

particular detonation.

  2. Many manufacturers are now

putting chemical tags in their explosives that will allow for

tracking of specific batches by chemical composition.

 IX. FORENSIC PSYCHIATRY AND PROFILING

  A. Forensic Psychiatry defines mental

illness and disorders, what creates them, how they are diagnosed and how they are treated.

  1. Mental illness cases: the

individual does not function well in reality because of emotional fluctuations or distorted point of view interpretation.

2. Mental disorder cases: a clinically

significant behavior or pattern associated with distress,

disability or significant risk of suffering death.

  B. Diagnosis is a medical

classification that allows for communication between

professionals, allows for prediction of illness and indicates the best course of treatment.

  C. The issue of incompetency

is fitness to stand trial.    1. The accused must

understand what is going on in order to help in their own defense.

 

2. The three grounds for incompetency are:

a. emotional/psychological

factors,

b. cognitive or intellectual factors,

c. and physical factors.  

 3. An individual must undergo a

competency evaluation if this assertion is made.

 

  D. The issue of insanity applies to

the mental state of the defendant at the time the crime was committed.  

  1. The defendant must

concede guilt when entering the insanity plea.

  2. The defendant claims to have

committed the crime while mentally impaired and did not know right from wrong or what they were doing.  

  3. The defendant must prove they

have a profound defect of mental ability.  

E. Profiling is the process by which a trained forensic psychologist examines the aspects of a crime scene to develop a description of the personality of the perpetrator.

  1. This profile can include: 

a. age, sex, occupation, upbringing,

b. behavioral disorders, marital status,

c. the type of place the perpetrator would live in,

d. what type of car he drives,

e. if he has a speech impediment,

f. or some other type of disability.

  2. Profiles can tell you how

the crime was committed.   

a. Information can be learned about the perpetrator of a serial crime just by looking at how that crime was

committed.  

  F. Profiling works because countless

hours have been spent interviewing hundreds of convicted criminals, learning about their crimes, motives, methods and personalities.  

  1. These databases help investigators

in making conclusions from what they view at a crime scene.

  2. Databases draw on thousands

of man-hours of research and interviews and has proven to be extremely accurate.

  G. Profiling does not produce a name.  

 

1. It does produce a detailed personality profile of aperpetrator that investigators can use to focus an investigation.

 X. QUESTIONED DOCUMENT EXAMINATION   A. This area of forensics involves

all special relationships that may exist between document and inscription and how it relates to a person or sequence of events.

1. This includes forgery, counterfeiting, and handwriting analysis.

  B. Questioned document

examination involves many areas of expertise.  

  1. Included are the following

disciplines:   a. handwriting, typewriting,

b. photocopying and computer printers,

c. forgery, paper and inks, writing instruments,

d. computer disks, gambling machinery,

e. stamps (as in the rubber pad kind)

f. and the dating of documents.

 

  C. Handwriting analysis 

1. Handwriting analysis involves detailed examination of the design, shape and structure of handwriting to determine

authorship of a given handwriting sample.

  2. The basic principle underlying handwriting analysis is that no two people write the exact same thing

the exact same way.    

a. Each individual develops unique peculiarities and characteristics in their handwriting.  

  3. Handwriting analysis looks at: a. letter formations,

b. connecting strokes between the letters,

c. upstrokes, retraces, down strokes, spacing,

d. curves, size, distortions, hesitations,

e. and a number of other characteristics of handwriting.

 

  4. By careful examination a

determination can be made as to whether or not the authorship of a handwritten document is genuine.

 

  D. Typewriting 1. Individual characteristics

are either inherent in the machining process of a

manufactured item, or come about through the

wear and tear in the use of an object.  

a. All typewriters of a particular make and model are pretty much the same.   (1) Through use, typewriters will

develop defects that translate to paper when the machine is used.  

(2) The defects left on the typed page can be matched back to the typewriter that was used to create it.

b. Defects in the type face can be identified by:

  (1) letter misalignment

(2) a letter failing to print evenly

  c. Ribbons are a major

evidentiary component.    (1) It is possible to read a

ribbon to see what it has been used to type.

  E. Photocopiers and Laser Printers. 1. Photocopiers and laser

printers use the same type of process to print a page.

 

  2. With a photocopier, the original

document is placed on the glass platen.   a. By use of a reflected light the

document is exposed to a drum covered with a photosensitive material.  

  b. The document image exists on the

drum as an invisible positive photoelectric charge.  

 c. Negatively charged toner

(a powder), is sprinkled onto the drum, where it sticks to only the positively charged areas to create a visible image.

  d. Paper, with a positive charge,

passes the drum resulting in the negatively charged toner being transferred to the paper.  

 e. The toner is heat sealed

to the paper, creating the printed copy.

  3. With a laser printer, the image of

the original document is held by a computer in its memory.

  a. The document is then

sent to the photosensitive drum by use of a laser creating a printed copy.

  4. There are several ways to match a page

back to a photocopier or laser printer:    a. The paper itself can yield many

clues.   (1) Look for marks from the

belts, pinchers, rollers and gears that physically move the paper through a machine.

b. How the toner was placed on and fused to the paper may leave unique characteristics.   (1) Toner may clump up on the drum,

transferring smears or splotches of toner at atime to the printed page.  

  c. Marks on the optics (glass platen,

lenses, mirrors) used to transfer or create an image on paper might contain unique defects like scratches that will leave tell tale

marks on the printed page.

  F. Forgery   1. Forgery is the false making

or material altering of any written document with

intent to defraud.

 

2. There are four basic types of forgery.   a. Traced  (1) There are several ways

to make a traced forgery:  

(a) by use of overlays (tracing paper),

(b) by the use of transmitted light (as with a light board),

(c) by tracing the indentations

left in the page underneath the original writing

  b. Simulation  (1) Copying of writing from a

genuine article; trying to imitate the handwriting

of the original.  

 (2) Simulation forgeries are easy

to detect.  (a) It is very difficult to copy

someone else’s handwriting.  

(b) The style will not be as fluid.

(c) The forged writing will show tremors, and hesitations in letter quality.

 c. Freehand   (1) Forgeries written with no

knowledge of the appearance of the original; just writing off the top of your head and passing it off as something else.

(2) Freehand forgeries are the easiest to detect.

d. Lifted  

(1) In this type forgery, tape is used to lift off a signature, then place it on another document.

 this concludes

Crime Scene Investigation