Criminalisticsjj

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C h a p t e r 1

IntroductionTo

Criminalistics

CHAPTER OVERVIEW

Criminalistics is the professional and scientificdiscipline dedicated to the recognition, collection,identification, and individualization of physicalevidence and the application of the natural sciencesto the matters of law. Forensic science is theapplication of science to the law. Criminalistics isbased on diverse scientific disciplines. Criminalisticsdraws upon chemistry, biology, physics, andmathematics to relate physical evidence to crime.

CHAPTER OBJECTIVES

At the end of this chapter you will be able to do thefollowing:

1. Define the term evidence.

2. Identify the reasons why physical evidence is important

to criminal investigations.

3. Provide practical examples of the application of

physical evidence to criminal investigations.

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Physical evidence has the potential to play a critical role in the

resolution of a suspected criminal act. This objective is furthered by the

thoughtful, objective and thorough approach to the investigative

process. The foundation of forensic science is the preservation of

physical evidence that will provide reliable information to aid in an

investigation.

In order to appreciate the importance of forensic science, the basic

principles must be understood. These principles include proper identifi-

cation and collection of evidence at a crime scene; knowledge of the best

practices in the field of criminalistics; the importance of firearms, docu-

ments, tool marks, impressions, DNA and trace evidence to the field of

criminalistics; and crime scene management. Proper crime scene man-

agement includes identification, evaluation, collection and preservation

of evidence, thorough search practices, and protection of the scene.

A HISTORICAL PERSPECTIVE

The origins of forensic science can be traced to the 1800s. During

this era, forensic specialists were self-taught. There were no special

schools, courses or formal training. One of the first significant

applications of forensic science occurred in 1888 in London, England.

During the late 1880s, Jack the Ripper had committed several serial

murders in London. Doctors were allowed to examine victims of Jackthe Ripper for wound patterns.

The use of fingerprint evidence in solving crimes today seems

routine and unremarkable. During the 1800s however, fingerprints

were the subject of intense scientific research. During the 1880s it was

discovered that fingerprints are unique to an individual and remain

unchanged over a lifetime. This discovery led to the identification of

offenders in criminal investigations.

The Points of Comparison Method

At one time around 1900, there was a

system called the anthropometric system that

had been invented by a Frenchman, Alphonse

Bertillon (1853-1914), consisting of numerous,

minute body measurements, such as finger and

forearm lengths. This system was in

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competition with fingerprinting (technically called dactylography),

discovered by Henry Faulds and popularized by Francis Galton.

Bertillon based his system on the use of 11 points of comparison,

calculating his odds of being wrong on any given match being 4 million

to 1. These types of calculations form the basis of a number of forensic

sciences relying upon the Points of Comparison method, such as

odontology, firearms examination, and questioned document

examination. Due to population growth since Bertillons time, the

contemporary method is based on at least 12 points of comparison and

an odds ratio of about 6 million to 1. An odds ratio or percent chance of

being wrong also characterizes the quantitative information provided by

modern analytical techniques such as spectrography, chromatography,

and DNA typing (in the case of DNA, the odds ratio is an amazing 30

billion to 1).

Other milestones in the development of criminalistics during the

1800s were:

The first recorded use of questioned document examination.

The development of tests for the presence of blood in a

forensic context.

A bullet comparison used to catch a murderer.

Comparison of a bullet and/or expended cartridge case to a

known firearm.

The first use of toxicology, specifically arsenic detection, in a

jury trial.

The development of the first crystal test for hemoglobin using

hemin crystals.

The development of a presumptive test for blood.

The first use of photography for the identification of criminals

and documentation of evidence and crime scenes.

The first recorded use of fingerprints to solve a crime.

Development of the first microscope with a comparisonbridge.

During the 1900s forensic science developed into a formal

academic discipline. One of the first steps in this progression was the

establishment of a forensic science curriculum in 1902 by Swiss

Professor R. A. Reiss at the University of Lausanne, Switzerland. This

led to the formation of university courses and degrees in criminalistics

and police science during the 1930s. Criminalistics made significant

Chapter 1 Introduction To Criminalistics 3


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advances along with the rise in technology during the 1900s. The

following are some of these advances:

Establishment of the popular practice of using the comparison

microscope for bullet comparison in the 1920s.

Development of the absorption-inhibition ABO blood typing

technique in 1931.

Invention of the first interference contrast microscope in 1935

by Dutch physicist Frits Zernike (Received Nobel Prize in

1953).

Development of the chemiluminescent reagent luminol as a

presumptive test for blood.

Study of voice print identification.

Invention of the Breathalyzer for field sobriety tests.

Use of heated headspace sampling technique for collecting

arson evidence.

Development of the scanning electron microscope with

electron dispersive X-ray technology.

Identification of the polymorphic nature of red blood cells.

Enactment of the Federal Rules of Evidence (1975).

Establishment of one of the first academic departments of

criminology/criminalistics at the University of California at

Berkley (1950).

American Academy of Forensic Science (AAFS) was formed

in Chicago.

Evaluation of the gas chromatrograph and the mass

spectrometer for forensic purposes.

Development of the polymerase chain reaction (PCR)

technique for clinical and forensic applications.

Use of DNA to solve a crime and exonerate an innocent

suspect (1980).

Introduction of DNA and the challenge of certification,

accreditation, standardization and quality control guidelines

for both DNA Laboratories and the general forensic

community (1987).

WHAT IS EVIDENCE?

Evidence is defined as information submitted in a legal proceeding

that establishes or disproves an alleged set of facts. Evidence is the basis



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of anycriminal charge. Without evidence to support a charge of criminal

wrongdoing, this allegation would be unable to be proven. The standard

of proof in a criminal case is that any allegation must be proven beyond a

reasonable doubt. This is a very high burden of proof. In a non-criminal

case, such as a contract dispute or a small claims action, the standard is

much lower. The standard of proof in these cases in based upon a

preponderance of the evidence. This means an allegation is more likely

true than not true. A preponderance of evidence can be translated to a

standard of proof over 50%. Beyond a reasonable doubt is a much harder

standard to meet. In contrast, the beyond a reasonable doubt standard

calls for an excess of 90% standard of proof.

Evidence collected at a crime scene plays a vital role in any criminal

investigation. This evidence may prove that a crime has been

committed, link a suspect to the scene or victim, establish the identity of

a suspect or victim, corroborate witness accounts, and exonerate

innocent parties. Evidence gathered at a crime scene also provides leads

for investigators to follow up on. Physical evidence is a real, tangible

object present at the crime scene. Physical evidence can take a variety of

forms at a crime scene. At the scene of a burglary investigation,

impressions such as fingerprints, tool marks, foot ware impressions and

tire marks are examples of physical evidence that may be collected.

Biological, trace, firearm evidence and questioned documents are also

examples of physical evidence. Biological evidence includes blood,

semen, cellular material, body fluids, hair, nail scrapings, and blood

stain patterns. Weapons, gunpowder patterns, cartridge cases,

projectiles, fragments, pellets, wadding, metallic residues, and projectile

wounds or impacts are examples of firearm evidence. Questioned

document evidence includes handwriting, mechanically produced text,

papers, writing implements, inks, and anything upon which a symbol

can be placed.

Bioscience in Action: Interesting Cases

Rape Investigation. An incapacitated woman claimed she was

raped at a party in Albany, New York. The woman was unable to

identify her attacker. Albany City Police secured and submitted blood

specimens taken from eight males present at the party. DNA patterns

were developed for all eight suspects. The results of the DNA analysis

directly implicated one of the eight subjects in the rape.



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Homicide Investigation. An accomplice to a murder told police

investigators that his partner had murdered a man, moved the body from

the crime scene in a vehicle and threw the body from a bridge. DNA

analysis confirmed this witnesss account of the incident. Investigators

found the victims blood at the crime scene, in the vehicle used to

transport the victim and on three garden tools used in the murder. An

examination of the bridge from which the victim was thrown over,

revealed hairs on the railing. Based upon this finding, the exact site from

which the body was thrown was identified.

THE IMPORTANCE OF PHYSICAL EVIDENCE

The value of physical evidence in a criminal investigation cannot be

understated. An individuals guilt or innocence can hinge upon evidence

collected at a crime scene. This type of evidence is more reliable than

eyewitness accounts of an incident. Over time, peoples memories can

fade. There is a tendency of people to fill in parts of an incident that they

did not see in its entirety. In contrast to eyewitness testimony, physical

evidence does not change. A fingerprint taken from a crime scene ten

years ago is equally as reliable as if it were collected today.

Physical evidence can prove that a criminal act did in fact occur and

it can establish key elements of the offense. The crime of rape generally

defined is sexual intercourse against the victims will or consent.Physical evidence such as torn clothing and bruising of the rape victims

body support the lack of consent element of this crime.

A suspect can be placed in direct contact or in close proximity with

the victim or crime scene. In a sexual assault or rape case, a sample of the

suspects semen may be collected from the victims body. Through the

use of DNA analysis this evidence can be used to identify the suspect

and place that suspect in contact with the victim.

Physical evidence can establish the identity of a suspect or person

associated with the crime. At the scene of a burglary, a fingerprint found

at the point of entry can identify as suspect and place that suspect at the

scene. A person may be exonerated or eliminated as a suspect in an

investigation based upon physical evidence. Individuals have been

released from prison after being ruled out of a crime by DNA analysis.

In an interview or interrogation situation, physical evidence can play

a critical role. In a bank robbery investigation, a suspect is identified and



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questioned. This suspect adamantly denies being involved in the

robbery. When confronted with a video surveillance tape of the robbery

clearly identifying him/her, the suspect confesses to the crime.

A victims statement or testimonycanbe corroborated. In a domestic

violence case, a female victim claims to have been struck numerous

times by her partner, causing significant bleeding. The victims spouse

is later contacted and has blood on his hands and clothing. The suspect

claims this blood is his own from an accident at home. Analysis of the

blood on the suspects handsand clothes determines that it belongs to the

victim, thereby corroborating her statement. Physical evidence may also

be used in the alternative, to discredit an untruthful victim. In a burglary

investigation, the lack of physical evidence, such as no signs of forced

entry, may indicate that a victim is being untruthful. This lack of

evidence may indicate another criminal act entirely, such as insurance

fraud.


Title: National Conference on Science and the Law

Proceedings.

Series: Research Forum

Author: National Institute of Justice

Published: NIJ, July 2000

Subject: Criminal Justice System

Preface

The intersections of science and law occur from crime scene to

crime lab to criminal prosecution and defense. Although detectives,

forensic scientists, and attorneys may havedifferent vocabularies and

perspectives, from a cognitive perspective, they share a way of

thinking that is essential to scientific knowledge. A good detective, a

well-trained forensic analyst, and a seasoned attorney all exhibit

what-if thinking. This kind of thinking in hypotheticals keeps adetective open-minded: it prevents a detective from ignoring or not

collecting data that may result in exculpatory evidence. This kind of

thinking in hypotheticals keeps a forensic analyst honest: it prevents

an analyst from ignoring or downplaying analytical results that may

be interpreted as ambiguous or exculpatory evidence. This kind of

Figure 1.1 The Importance of Physical Evidence and the Law


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thinking in hypotheticals keeps attorneys thoroughly prepared: it

prevents a prosecutor from ignoring alternative theories of the crime

that will surely arise in the defense, and it keeps the defense open to

raising alternative theories. Our adversarial system of justice relies

on thinking in hypotheticals, examining each possibility, looking at

all the angles because we expect proof beyond a reasonable doubt.

We have already seen too many times what happens when

what-if thinking breaks down. Consider what happens when a

detective refuses what if thinking. Exculpatory evidence is not

collected at the crime scene; an innocent person may be convicted.

Evidence is collected in such a sloppy manner that it cannot be

processed by the crime lab; a guilty person may be set free. Consider

what happens when a forensic analyst refuses what if thinking. A

crime lab technique has been accepted for the last 50 years; no one

has questioned its validity or reliability because everyone just

believes that it works; people may be wrongfully convicted or

exculpated by a scientifically unsound technique that is presented as

scientific evidence. Or consider what happens when what if

thinking breaks down in the courtroom. Judges naively accept

whatever scientists with a particular set of credentials tell them, the

scientist-witness is allowed to represent both the opinions of the

entire scientific discipline as well as specific opinions with regard to

the case, and the expert witness industry is thriving.

Currently, the criminal justice profession has several

mechanisms for ensuring that what-if thinking does not break

down. Daubert, and now Kumho, hearings can highlight serious

deficiencies in traditionally accepted forensic sciences. Training for

judges and lawyers can upgrade their ability to determine the value of

scientific evidence and to distinguish between good investigativeleads, which may result from pre- scientific techniques, and solid

scientific evidence, which derives from the scientific method.

Research by academics or scientific organizations such as the

National Academy of Sciences can provide answers to

methodological dilemmas, which face any science moving from the

Figure 1.1 The Importance of Physical Evidence and the Law (cont.)


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laboratory to the crime scene. Law enforcement training can provide

detectives and departments with best practices for investigation and

evidence collection, such as the National Institute of Justices recent

publication on crime scene investigation. Technical working groups

that are discipline based, such as the National Institute of Justices

Technical Working Group on Eyewitness Evidence, can provide

checks on scientific and investigative procedures and interpretation

of results.

But even with such homologous ways of thinking, judicial

decisions, and educational safeguards in place, science and law

continue to be uneasy partners. Questions about this partnership form

the basis for the following papers, from scientists, attorneys, and

judges, which all address, from differing aspects, the relationship

between science and law. It is hoped that by facing these questions

directly we shall find answers that enable us to use science and law in

the service of truth and justice.

Carole E. Chaski, Ph.D.

Executive Director Institute for Linguistic Evidence, Inc.

Georgetown, Delaware

Source: The entire report can be viewed at:http://www.ncjrs.org/txtfiles1/nij/179630.txt

Figure 1.1 The Importance of Physical Evidence and the Law (cont.)

A criminalist (aka crime scene technician, examiner, or

investigator) is a person who searches for, collects, and preserves

physical evidence in the investigation of crime and suspected

criminals. They typically work in city or regional crime labs and are

expected to do more than the forensic scientists and crime lab

technicians there. They are expected to be on call 24 hours a day to go

out to crime scenes, frankly when and where detectives are stumped.

Some jurisdictions require the presence of a criminalist at all major

crime scenes. The services of a criminalist are used at the beginning

of a case. By contrast, the services of a forensic scientist are primarily

Figure 1.2 An Introduction to Criminalistics and Physical Evidence


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used at the end, or courtroom testimony phase, of a case. All crime lab

employees must be ready to offer expert testimony in court, however.

Criminalists usually get called to testify about matters of

contamination, cross-contamination, and chain of custody, but many

of them (senior criminalists) have developed an interpretive

expertise, for example, in blood spatter analysis, trace evidence,

impression evidence, or drug identification, as well as skills at crime

reconstruction and sometimes profiling (Levinson & Almog 1989).

The term criminalistics (Kriminalistik) was first used by Hans

Gross in 1891, but the term was mostly forgotten until the 1960s

when a series of cooperative movements took place between police

agencies and criminal justice or criminology departments to establish

criminalistics (University of California, Berkeley) and forensic

science (Michigan State) college programs. Professors Paul Kirk in

California and Ralph Turner in Michigan (among many others) were

pioneers in those movements. As Osterburg and Ward (2000) imply,

criminalistics programs followed the police science model to record,

identify, and interpret the minutia (minute details) of physical

evidence, and forensic science followed the medical science model to

apply generally accepted principles of established disciplines (like

pathology, serology, toxicology, odontology, and psychiatry) to the

scientific examination of physical evidence. Forensic science is the

broader term because criminalistics is a branch of forensic science.

Forensic is simply an adjective that can be put in front of any

science applied to answering legal questions. The American

Academy of Forensic Sciences web site highlights about twenty

various degree programs that relate to some aspect of criminalistics

or forensic science education.

The worlds first crime laboratory was established by EdmondLocard in Lyon, France during 1910. The famous Locard Exchange

Principle that every contact leaves a trace is named for him, after

Locard solved a strangling case by using fingernail scrapings. In

America, a few major cities and the FBI obtained crime labs during

the 1930s, and by the mid-1970s (the birth of criminal justice), 47

states had crime labs. A few criminal justice programs that existed

Figure 1.2 An Introduction to Criminalistics and Physical Evidence (cont.)


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prior to the explosion of the field in 1974 offered a criminalistics or

forensic science concentration, but today, most criminal justice

programs only have one course in criminal investigation. Post-1975,

the criminal justice model became an attempt to make sense of whole

systems of justice, and the criminology model, dominated heavily by

sociology until about 1990, became theory, research, and

policy-driven. Many criminalists consider themselves (professional)

criminologists, but few criminologists consider themselves

criminalists.

THE IMPORTANCE OF CRIME LABS

With federal police agencies, two (2) organizations stand out

above the rest, the FBI and ATF, mainly because their crime labs are

pretty much considered the tops in the field and a model for

elsewhere.

The FBI laboratory has 4 sections: (1) Scientific analysis (DNA,

Firearms-toolmarks, Hairs and Fibers, Materials Analysis, Chemistry

and Toxicology, Questioned Documents; (2) Special Projects (film,

photography, composites, art, computer design); (3) Fingerprinting

(some 200 million records); (4) Investigative Operations and Support

(grew out of Questioned Documents unit and includes lie detection ofvarious sorts). The FBI lab only handles violent crime, works

exclusively for the prosecution, and is considered the worlds largest

lab.

The ATF laboratory handles (1) Explosives, bombs, arsons (and

does it well); (2) Trace evidence and deciphering firearms ownership

and usage; (3) Disaster response teams (kind of like FEMA); (4)

Field support; and (5) some Gang intelligence record keeping. ATF

labs are typically very high-tech and have always been accredited.

Its typical for a Crime Lab to have 4 divisions under a Directors

Office: (1) a section dealing with anything pertaining to fluids, this

being called a Serology Division; (2) a section dealing with unknown

substances, drugs, or poisons, this being called a Chemistry or

Toxicology Division; (3) a section dealing with anything so small,

like hairs or fibers, that they need to be looked at under a microscope,



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this being called a Trace Evidence, Biology, or Microscopy Division;

and (4) a section dealing with guns, weapons, instrumentation, or

whatever, this being called a Ballistics, Firearms, or Fingerprinting

(Dusting and Lifting) Division (where Interns usually work).

There are about 350 crime laboratories in the U.S. and at least

80% of them are affiliated with a police agency (where they typically

hold bureau status in the organization). The rest are located in the

private sector and some of these are exemplary and known for a

particular specialty: Cellmark Diagnostics (for DNA), Battelle Corp.

(for arson cases), and Sirchie Corp. (for fingerprinting and trace

evidence collection), to name a few. There is a shortage of DNA

laboratories since only 120 labs are set up to do DNA testing

(Steadman 2002). Almost all labs in existence are forensic labs,

where forensic means the experts there are available to give

courtroom opinions, but when a lab is set up to receive evidence from

ongoing criminal investigations, this is called casework, and the lab

is referred to as a casework lab.

You cant just start up a crime lab anywhere or anytime you feel

like it. Things are set up geographically so that on average, a lab is

almost always 50 miles within 90% of the police agencies. There aresome places that buck this pattern, but usually each state has one

parent lab and 5-6 regional labs. They are always hiring and

looking for help, as theres a labor shortage of qualified applicants.

Theres also usually a work backlog, and some labs and state systems

are so backed up, that it takes many months to get the results back on

an evidence analysis. But in all fairness, the backlog situation should

not be a concern because crime labs were never intended to replace a

field investigation. The point of this is that police investigators

should never come to rely on a crime lab, but use it as a supplement totheir own investigative skills. Criminalistics and forensic science are

not silver bullets.



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THE PROBLEMS OF CRIME LABS

Chain of Custody

There are many sources of error. Evidence has to be discovered

(police or criminalist), it has to be collected (police, crime scene

technician, or criminalist), and then it has to be packaged, labeled,

and transported (police supervisor or criminalist). Once it gets to the

lab, it has to be logged in, assigned an identification number, placed

in storage, kept from intermingling with other evidence, and analyzed

(criminalist, crime lab technician, or forensic scientist).

Before any laboratory work is done, it must be ensured that the

workplace is clean and contamination free. Then, the evidence is

visually inspected and properly described to document its condition.

Often, it will be photographed, weighed, and sketched. Then, the

laboratory worker (criminalist, crime lab technician, or forensic

scientist) will have to figure out what tests are appropriate, if

sufficient amounts of the evidence exist, properly dissect the portion

to be tested, and properly prepare the testing material (which might

include the delicate mixing of numerous chemical compounds), all

the while continuing to document each step. Only then does any

testing begin.

Some tests include as many as five or six separate procedures,

each of which must be properly performed and documented, the

evidence properly repackaged and relabeled, and once again

transported to storage. Only then does the lab worker engage in the

process of interpreting what the experiments have disclosed. A report

is prepared and the contents of that report must be precisely correct.

At the prosecutors discretion, the evidence has to make it back to

the police evidence room, where it will be stored until he/she decidesthey want to use it or want more testing performed, in which case it

goes back to the crime lab. It should be fairly evident that all this

transportation of evidence gives rise to numerous possibilities for

error in the form of destruction, mishandling, and contamination.



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Integrity

Its important a crime lab find some system for establishing its

credentials as a forensic laboratory. A couple of the organizations

that perform this function include the American Society of Crime

Laboratory Directors (ASCLD), the National Forensic Science

Technology Center (NSFTC), and the College of American

Pathologists (CAP). In addition, labs that specialize may also apply

for credentials from an organization, or Board, which regulates that

specialty. For example a lab that performs odontological work might

apply to the National Board of Forensic Odontology.

Generally, whenever a lab applies for accreditation, it has to meetcertain minimum requirements, which include, among other things,

the development and publication of:

A Quality Control Manual - Quality control refers to

measures that are taken to ensure that the product, for

example a DNA-typing result and its interpretation, meets a

specified standard of quality.

A Quality Assurance Manual - Quality assurance refers to

measures that are taken by a laboratory to monitor, verify,

and document its performance. A basic business principle is

that QA serves as a check on QC.

A Lab Testing Protocol - Protocols consist of a few hundred

pages of highly technical manuals and should include such

things as validation studies which the lab performed itself

to make it capable of performing tests in any particular

discipline.

A program for proficiency testing - Proficiency testing

determines if the lab workers individually, and the

laboratories as institutions, are performing up to the

standards of the profession. In these tests, samples to beexamined are given to a laboratory or particular worker, but a

test giver already knows the results. There are two methods

employed in administering these tests, blind and known. In

the blind test, the lab worker doesnt know that a test is taking

place; they think the evidence sample they are working on is

just another case. The open proficiency test is like an open



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book exam. In addition, individual lab workers join

associations to beef up their resumes. The two main ones are

the American Academy of Forensic Sciences (AAFS), theAmerican Board of Criminalistics (ABC).

In general, attacks on laboratory expertise come in three

categories (which are the same techniques for attacking physical

evidence):

Tampering - Tampering refers to allegations that the crime

scene or piece of evidence was tampered with. Theres a

presumption of regularity on the side of the prosecution, so

this is hard to prove.

Contamination - Contamination is somewhat easier to allege,given irregularities in the chain of custody.

Substitution - Substitution (or mistake) is a problem if the lab

workers are new, inexperienced, or lack the appropriate

credentials.

THE BASICS OF PHYSICAL EVIDENCE

Physical evidence is part of the holy trinity for solving crimes

physical evidence, witnesses, and confessions. Without one of the

first two, there is little chance of even finding a suspect. In homicide

and sexual assault cases, physical evidence is the number one

determinant of guilt or innocence. Physical evidence is also the

number one provider of extraordinary clearances, where police can

link different offenses at different times and places with the same

offender. Working with physical evidence means being aware at all

times of what the prosecutor needs to win the case in court. This

means knowing the Types of Evidence and the Laws of Evidence.

Four Types of Evidence:Testimonial

This is the kind of evidence that comes to court through witnesses

speaking under oath or affirmation. They could be testifying about

something they saw (eyewitnesses), something they heard (hearsay

witnesses), or something they know (character, habit, or custom

witnesses).



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Physical

These are tangible objects that are real (sometimes said to speak

for themselves because they can be taken into the jury room), direct

(no preliminary facts needed), and not circumstantial (do not require

an inference to be made), although circumstantial evidence is

sometimes offered and strengthened by expert testimony. Examples

of physical evidence would include the gun used to commit the crime,

trace particles found at the crime scene, property recovered,

fingerprints, shoeprints, handwriting, etc.

Documentary

This is usually any kind of writing, sound or video recording. It

may be the transcript of a telephone intercept. Authentication of the

evidence is usually required along with expert testimony at times.

Demonstrative

These are types of real evidence used to illustrate, demonstrate, or

recreate a tangible thing, for example, a cardboard model mockup of

the crime scene or other constructed-to-scale models. The purpose of

this stuff to replace timely, expensive, and possibly prejudicial jury

trips to the crime scene.

Both forensic scientists and criminalists need to be intimatelyfamiliar with the Standards of Admissibility for Scientific Expertise,

since these vary from state to state, and sometimes even from court to

court within states.

Relevancy test (FRE 401, 402, 403) - this is embodied in the

Federal Rules of Evidence and state versions which essentially

involve a liberal rule allowing anything that materially assists the

trier of fact (jury) and is deemed relevant by the trier of law (judge).

Frye Standard (Frye v. U.S. 1923)

For the results of a scientific technique to be admissible, the

technique must be sufficiently established to have gained general

acceptance in its particular field. This is the general acceptance test

that often requires knowledge of the literature.



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Coppolino Standard (Coppolino v. State 1968)

The court allows a novel test or piece of new, sometimescontroversial, science on a particular problem at hand if an adequate

foundation can be laid even if the profession as a whole isnt familiar

with it.

Marx Standard (People v. Marx1975)

The court is satisfied that it did not have to sacrifice its common

sense in understanding and evaluating the scientific expertise put

before it. This is the common sense or no scientific jargon test,

and it is rarely used Daubert standard (see Lecture on Daubert). This

test requires special pretrial hearings for scientific evidence andspecial procedures on discovery. This is a rather stringent test that

requires knowledge of Type I and Type II error rates, as well as

validity and reliability coefficients.

CONCEPTS AND PRINCIPLES OF PHYSICAL EVIDENCE

Since criminalistics is the recording, identification, and

interpretation of minutia (minute details), a number of standard

techniques and procedures have been developed to do this. It is

important to understand the basic concepts behind these techniques.

A more useful term than minutia is striations, which are scratch

marks caused by irregularities or lack of microfine smoothness, such

as those found on fingerprints, bullets, cartridges, casings, or tool

marks. With evidence like paint, hair, grease, and glass, the chemical

composition (qualitative and quantitative) provides the details. With

other types of evidence, such as glass fragments, the morphology (or

form) of an object reveals valuable information, such as a jigsaw

puzzle fitlinking pieces of broken glass together.

Criminalists know how to operate a variety of devices andmachines. The three simplest devices are lights, camera, and

microscope. By adjusting the light on an object, the morphological

and composition characteristics of evidence often become visible. A

basic principle is contrast, as in when the background color of an

object is made different than the foreground color. Cameras often

allow the use of lens filters to screen out certain colors, and contrast



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(among other things) can be increased or decreased in photography.

Microscopes are the main technique for enlarging resolution,

although it is possible to enlarge without enhancing resolution. Most

physical evidence reveals valuable detail at magnifications between

2x and 10x. The more complex devices are called analytical

instruments, and consist of the following:

Table 1 Analytical Instrument

Instrument Substance Effect of Sample Information

Spectrophotometers Organic/Inorganic Nondestructive Quantitative

Mass spectrography Organic Destructive Qualitative

X-Ray Diffusion Crystalline Nondestructive Qualitative

Neutron Activation Inorganic Nondestructive Qualitative/Quantitative

Scanning Electron Organic/Inorganic Nondestructive Semi-quantitative

X-Ray Dispersion Inorganic Nondestructive Qualitative

Chromatography Organic Nondestructive Qualitative/Quantitative

There are many more organic substances than inorganic

substances. Most drugs, explosives, hairs, and biological fluids are

organic, based on the element carbon. Most dirt, gunpowder, poisons,

paint, and glass are inorganic, although some substances represent a

mix or organic and inorganic.

Without doubt, the most important concept in criminalistics is

identification, or what Paul Kirk called individualization (Kirk

1936). Identification produces unequivocal (certain) interpretation.

An equivocal crime scene, by comparison, yields physical evidence

subject to different interpretation (and is the basis for crime

reconstruction and profiling). When a number of details are put

together (as in points of comparison), so that they constitute a class of

one (by itself), they are said to establish an identity, also called

individual characteristics, or entities in a class by itself. At this point,

if there are similarities between evidence from the crime scene and

evidence from a suspect, the expert can say, without a doubt, that

identity has been individualized.



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It is important to clearly understand the concepts of identity,

match, class and individual characteristics. Identity is a set of

characteristics (combinations of class characteristics or combinations

of class and individual characteristics) by which a thing is

recognizable or known. Identity is the same as pattern. A pattern is

established, for example, when a particular piece of class evidence

like fiber (for which there are large quantities in the population) is put

together with another piece of class evidence like red hair (which

usually only exists in the subpopulation of white people). It cannot be

said the investigator has individualized anything at this point, but

the red hair in this example can be considered enough of an individual

characteristic, which combines with the class characteristic to

establish identity. At this point, if there is a match between the

fibers and hair from the crime scene with a suspect, the examiner can

say the crime scene (unknown or questioned) sample may have

come from the same source as the suspects (known or exemplar)

sample, which is sufficient for probable cause. Identity can also be

used to conclusively eliminate people as suspects.

Class characteristics alone do not allow matches with a single

suspect. Matches for evidence with individual characteristics do

allow pinpointing a particular suspect.Matches at the individual level

are called similarities, because in theory, theres no such thing as a

perfect match. An example of a similarity, or match in individual

characteristics, would be a number of comparable points of

comparison between the friction ridge lines on a latent (crime scene)

fingerprint with the fingerprints of a particular suspect. This kind of

(true) match allows the examiner to say that, because the similarities

outweigh any dissimilarities, the crime scene (unknown or

questioned) sample did come from the same source as the suspects

(known or exemplar) sample, which is sufficient, most of time, for

proof beyond a reasonable doubt.

Reliability and integrity are enhanced if the examiner has

conducted tests on standards using controls. A standard is the

opposite of exemplar. An exemplar always comes from a suspect or

something representing a known modus operandi or signature.



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Standards consist of simultaneous tests done on items taken from the

background or nearby the crime scene (control sample), itemssimilar to one the suspect used, such as test firings of a similar

weapon (standard sample), or items used for calibration purposes

kept in stock at the lab (reference sample).

The astute student may notice that the word match is used a

couple of different ways in criminalistics. Nobody uses the phrase

(true) match, for example, like I have used in my explanations above.

Some people prefer the term matching (Ramsland 2001). Abuse of

the term match is even worse in forensic science, which allows

different disciplines to set their own criteria and standards. To wrapthings up, lets conclude with an interesting topic, the points of

comparison method, and then attempt to present a table, which

classifies evidence by their class and individual characteristics.

THE POINTS OF COMPARISON METHOD

At one time around 1900, there was a system called the

anthropometric system that had been invented by a Frenchman,

Alphonse Bertillon (1853-1914), consisting of numerous, minute

body measurements, such as finger and forearm lengths. This system

was in competition with fingerprinting (technically called

dactylography), discovered by Henry Faulds and popularized by

Francis Galton. Bertillon based his system on the use of 11 points of

comparison, calculating his odds of being wrong on any given match

being 4 million to 1. These type of calculations form the basis of a

number of forensic sciences relying upon the Points of Comparison

method, such as odontology, firearms examination, and questioned

document examination. Due to population growth since Bertillons

time, the contemporary method is based on at least 12 points of

comparison and an odds ratio of about 6 million to 1. An odds ratio or

percent chance of being wrong also characterizes the quantitative

information provided by modern analytical techniques such as

spectrography, chromatography, and DNA typing (in the case of

DNA, the odds ratio is an amazing 30 billion to 1).



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SUMMARY

Modern day criminalistics has advanced along with technology from

its origins in the 1800s. The thorough, thoughtful collection of evidenceat a crime scene forms the foundation of a criminal investigation. The

importance of physical evidence cannot be underemphasized. This

evidence tells the story of a criminal offense. Physical evidence can

provide who, what, when, where and sometimes why in the resolution of

a criminal case.

DISCUSSION QUESTIONS

1. What are three examples of advances in criminalistics during

the 1900s?2. Provide at least three examples of the application of physical

evidence in a criminal case.

3 Why is physical evidence important in solving crimes?


There is no such thing as a comprehensive classification scheme

for all types of physical evidence. Some types of class evidence can

be somewhat individualized, such as hair and blood, and some

individual types are best considered both class and individual

evidence. With that having been said, heres a table that lays out some

basic distinctions:

Class Evidence Individual Evidence

Drugs Fingerprints

Fibers Toolmarks

Hair Handwriting

Blood DNA

Glass Firearms

Soil Shoeprints

Source: http://faculty.ncwc.edu/toconnor/315/315lect02.htm



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ADDITIONAL READINGS

Handbook of Forensic Services, United States Department of Justice,

Federal Bureau of Investigation: 1999 www.fbi.gov.

Advancing Justice through DNA Technology, Office of the President,

http://www. ojp. usdoj. gov March 2003Crime Scene Investigation, Office of Justice Programs, National Institute of

Justice, World Wide Web Site http;//www. ojp. usdoj.gov, 1999

An Introduction to Criminalistics and Physical Evidence; Tom OConner

Ph.D. North Carolina Wesleyan University http://faculty.ncwc.edu
