In its broadest definition, forensic science is
the application of science to criminal and civil laws.
The subject matter of this book emphasizes
the application of science to those criminal and civil laws that are enforced by police agencies in a criminal justice system.
Forensic science owes its origins to individuals such as
Bertillon, Galton, Lattes, Goddard, Osborn, and Locard,
who developed the principles and techniques needed to identify or compare physical evidence.
developed the principles and techniques needed to identify or compare physical evidence.
Bertillon, Galton, Lattes, Goddard, Osborn, and Locard
Bertillon, Galton, Lattes, Goddard, Osborn, and Locard, developed the principles and techniques needed to
identify or compare physical evidence.
The father of forensic toxicology.
Mathieu Orfila
Devised the first scientific system of personal identification in 1879.
Alphonse Bertillion
Bertillon's system of bodily measurements as used for the identification of an individual.
Conducted the first definitive study of fingerprints and their classification.
Francis Galton
Developed a procedure to determine blood type from dried bloodstains.
Leone Lattes
Used a comparison microscope to determine if a particular gun fired a bullet.
Calvin Goddard
Developed the fundamental principles of document examination.
Albert Osborn
Utilized microscopy and other analytical methodologies to examine evidence.
Walter McCrone
Wrote the first treatise describing the application of scientific principles to the field of criminal investigation.
Hans Gross
Incorporated Gross' principles within a workable crime laboratory.
Edmond Locard
Locard's Exchange Principle
States that when a criminal comes in contact with an object or person, a cross-transfer of evidence occurs.
The ever increasing number of crime laboratories is partly the result of:
- Supreme Court decisions in the 1960s responsible for police placing greater emphasis on scientifically evaluated evidence.
- Crime laboratories inundated with drug specimens due to accelerated drug abuse.
- The advent of DNA profiling.
The development of crime laboratories in the United States has been characterized by rapid growth accompanied by
a lack of national and regional planning and coordination.
At present, approximately ___ public crime laboratories operate at various levels of government�federal, state, county, and municipal.
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The technical support provided by crime laboratories can be assigned to five basic services:
1.) Physical Science Unit
2.) Biology Unit
3.) Firearms Unit
4.) Document Unit
5.) Photographic Unit
Physical Science Unit
incorporates the principles of chemistry, physics, and
geology to identify and compare physical evidence.
Biology Unit
applies the knowledge of biological sciences in order to
investigate blood samples, body fluids, hair, and fiber samples.
Firearms Unit
investigates discharged bullets, cartridge cases, shotgun shells, and ammunition.
Document Unit
provides the skills needed for handwriting analysis and
other questioned-document issues.
Photographic Unit
applies specialized photographic techniques for recording
and examining physical evidence.
Optional Services by Full-Service Labs
- Toxicology Unit
- Latent Fingerprint Unit
- Polygraph Unit
- Voiceprint Analysis
- Evidence-Collection Unit
Toxicology Unit
examines body fluids and organs for the presence of drugs
and poisons.
Latent Fingerprint Unit
processes and examines evidence for latent fingerprints.
Polygraph Unit
conducts polygraph or lie detector tests.
Voiceprint Analysis
attempts to tie a recorded voice to a particular suspect.
Evidence-Collection Unit
dispatches specially trained personnel to the crime scene to collect and preserve physical evidence.
The Scientific Method:
Formulate a question worthy of
investigation.
Formulate a reasonable hypothesis to
answer the question.
Test the hypothesis through
experimentation.
Upon validation of the hypothesis, it
become suitable as scientific evidence.
A forensic scientist must be skilled in applying the principles and techniques of
the physical and natural sciences to the analysis of the many types of evidence that may be recovered during
a criminal investigation.
A forensic scientist may also provide expert
court testimony.
An expert witness is an individual whom the court determines
possesses knowledge relevant to the trial that is not expected of the average person.
The expert witness is called on to evaluate evidence based on specialized training and experience that the court lacks the expertise to do.
The expert will then express
The necessity for the forensic scientist to appear in court has been imposed on the criminal justice system by the case of
Melendez-Diaz v. Massachusetts.
The Frye v. United States decision set guidelines for
determining the admissibility of scientific evidence into the courtroom.
To meet the Frye standard, the evidence in question must be
generally accepted" by the scientific community.
in the 1993 case of Daubert v. Merrell Dow Pharmaceutical, Inc., the U.S. Supreme Court asserted that
the Frye standard is not an absolute prerequisite to the admissibility of scientific evidence.
Trial judges were said to be ultimately responsible as "gatekeepers" for the
admissibility and validity of scientific evidence presented in their courts, as well as all expert testimony.
In Daubert, the Supreme Court offered some guidelines as to how a judge can gauge scientific evidence:
Whether the scientific technique or theory can be (and has been) tested.
Whether the technique or theory has been subject to peer review and publication.
The technique's potential rate of error. Existence and maintenance of standards controlling the techn
A number of special forensic science services are available to the law enforcement community to augment the services of the crime laboratory. These services include
forensic psychiatry, forensic odontology, computer science, and forensic engineering.
Forensic Psychiatry is an area in which
the relationship between human behavior and legal proceedings is examined.
Forensic Odontology involves
using teeth to provide information about the identification of victims when a body is left in an unrecognizable state; also investigates bite marks.
Forensic Engineering is concerned with
failure analysis, accident reconstruction, and causes and origins of fires or explosions.
Forensic Computer Science involves
the examination of digital evidence.
Many crime laboratories have
evidence technicians," trained by the crime lab staff, on 24-hour call for evidence collection at crime scenes.
Training ensures all pertinent evidence will be recognized and collected properly.
Where no formal training exists, familiarity can be gained
Upon arrival at a crime scene the first responding police officer to a crime scene is responsible for:
1.) Acquiring medical assistance for injured victims
- Medical personnel avoid disturbing evidence and approach the victim by an indirect route.
2.) Detaining any potential suspects or witnesses
- Statements are taken from victims, witnesses, and suspects
The boundaries of the crime scene must be secured with
crime scene tape, ropes, or cones.
The secured area should include
the area where the crime took place and the surrounding area where physical evidence may be located.
Once the boundaries are secured, guards may be posted to
restrict access to the crime scene.
A detailed log is kept of
personnel movements in and out of the crime scene. This log includes personnel names and time of entry or exit.
Investigators should never do anything that
might alter the crime scene including smoking, eating, drinking, or littering.
The search for physical evidence at a crime scene must be
thorough and systematic.
The search pattern selected will normally depend on
the size and locale of the scene and the number of
collectors participating in the search.
For a factual, unbiased reconstruction of the crime, the investigator, relying upon his or her training and experience, must not
overlook any pertinent evidence.
Physical evidence can be anything from
massive objects to microscopic traces.
the three methods for crime-scene recording
photography, sketches, and notes
Ideally all three should be employed; however, as is often the case, personnel and monetary limitations may prohibit the utilization of photography at every crime site.
Note taking begins when
the investigator is contacted and requested to report to the crime scene.
The crime scene notes should begin with:
The identity of person who contacted the investigator
Time of contact and arrival at the crime scene
Preliminary case information
Personnel present on arrival and those being contacted
Notes contain
a personnel log, all observations made by the investigator, and the time observations were made.
Notes are taken in a
uniform layout, concurrently as the observations are made.
Notes are written in
a bound notebook in blue or black ink.
A digital photograph is made when
a light sensitive microchip captures light on each of millions of tiny picture elements, called pixels.
The light is recorded on each pixel as a specific electric charge which is read by the camera as image information which is stored as a file on a memor
The number of pixels is directly related to
the resolution of the picture. Photographs with more pixels show increasingly good resolution, or more detail and sharpness in photographs.
The number of pixels that a camera features is usually measured in
millions of pixels, or megapixels.
Advantages of digital crime scene photography include
The ability to observe images immediately after taking them ensures important photographs are clear and show the best possible detail.
The resolution available can exceed 12 megapixels, while the maximum resolution offered by a film SLR camera is equivale
Crime scene photographs should record
the area in which the crime actually took place and all adjacent areas where important acts occurred.
The most important prerequisite for photographing a crime scene is
for it to be in unaltered condition.
Each crime scene should be photographed as completely as possible in
a logical succession. The sequence will show the overall scene first, then work down to individual pieces of evidence that jurors in the trial can easily relate back to the larger scene
The four minimum photographs required at a crime scene are
an overview photograph, a medium range photograph, a close-up photograph, and a close-up photograph with a scale.
which photos are taken first
overview photos
Overview photographs of the entire scene and surrounding area, including points of exit and entry, are taken first.
Taken from the outside borders of the scene and from various angles
If the crime scene includes a body, photographs must sh
what is a "visual tag
an object recorded in multiple overview photographs, to help visually piece the scene together
first photo
The sequence begins with an overview photograph of the entry to the victim's bedroom showing evidence markers in place.
second photo
The medium-range photograph shows the evidence marker next to the door denoting a cartridge case.
third photo
The close-up photograph shows the cartridge in detail with a scale in the photograph.
Medium-range photographs show
the layout of smaller significant areas of the crime scene.
Taken with evidence markers in place to show the spatial relationships between and among pieces of evidence in greater detail than the overview photographs.
medium-range photographs
Include at least one photograph of the "center" of the scene.
medium-range photographs
In violent crimes, this usually includes the site where the victim was found and the surrounding area.
medium-range photographs
taken last and show greater detail of individual objects or evidence.
close-up photographs
Taken at a 90� angle to the object, with and without evidence markers and scales.
close-up photographs
Scales should be placed as close to the evidence as possible without affecting it in any way.
After the 90� photographs have been taken, photographs from other angles may be taken.
The most important close-up photographs are those depicting
injuries and weapons lying near a body.
After the body is removed from the
scene, the surface beneath the body should be photographed.
As with still crime scene photography, the crime scene video must include
overview, medium-range, and close-up images.
A narrated crime scene video combines
photography and notes.
However, it is important that only one person narrates and no side conversations are captured on the video.
Some video cameras can produce still photographs, but
the quality is often poor.
Therefore, still photographs from a digital camera are still required.
initial survey of the crime scene
Walkthrough
The Walkthrough�initial survey of the crime scene
1.) Perpetrator's point of entry and exit are located.
2.) Indirect path is taken to the center of the crime scene.
3.) Obvious items of evidence are located and documented.
4.) The conditions of the scene are observed and recorded.
- Special attention is
Line/Strip Search Pattern
One or two investigators start at the boundary of the crime scene and search in straight lines across to the other side of the crime scene.
Grid Search Pattern
Two or more investigators form a grid by searching in line patterns that overlap and are perpendicular to each other.
Spiral Search Pattern
One investigator searches in a spiral path from the center of the crime scene to the boundary (outward) or from the boundary of the crime scene to the center (inward).
Wheel/Ray Search Pattern
Several investigators search in straight lines from the center to the boundary (outward) or from the boundary to the center (inward).
Quadrant/Zone Search Pattern
The crime scene is divided into smaller sections (zones). One or more investigators are assigned to search each zone.
Vehicle Searches
Investigators search interior and exterior of vehicle.
The vehicle may be searched at the crime scene or at the police department or crime laboratory garage.
Crime scene sketches
Clearly show the layout of a crime scene
Illustrate the relationship in space of all significant items and features
Clarify objects and features already described in notes or shown in photographs
Crime scene sketches show
measurements over long distances and topography of outdoor scenes
crime scene sketches depict possible
paths of entry, exit, and movement through the scene
A rough sketch is
created at the crime scene and contains an accurate
depiction of the dimensions of the scene and shows the location of all pertinent objects and features.
All rough sketches include
Title block with information on the case, crime scene, and person creating the sketch
Legend with identity and dimensions of objects in the sketch
Compass showing the North direction
Body containing the sketch itself
Points of reference for objects can be
rough crime scene sketch
The finished sketch is created from
the information in rough sketch, but it is drawn to scale with care and concern for appearance.
The current standard method utilizes Computer-Aided Drafting (CAD) programs to create the finished sketch. CAD programs also allow for the creation of three-di
finished sketch
Often, many items of evidence are clearly visible but others may be
detected only through examination at the crime laboratory.
it is important to collect possible carriers of trace evidence, such as
clothing, vacuum sweepings, and fingernail scrapings, in addition to more discernible items.
Investigators handle and process physical evidence in a way that
prevents changes to the evidence through contamination, breakage, evaporation, accidental scratching or
bending, or through improper or careless packaging.
reduces the chance for contamination.
The use of latex gloves, disposable forceps, and sanitized equipment
Whenever possible, one should keep evidence
in its original condition as found at the crime scene.
Each different item or similar items collected at different locations must be placed
in separate containers. Packaging evidence separately prevents damage through contact and prevents cross-contamination.
The well-prepared evidence collector will arrive at a crime scene with
a large assortment of packaging materials and tools ready to encounter any type of situation.
may have to be used to pick up small items.
Disposable forceps and similar tools
excellent containers for hairs, glass, fibers, and various other kinds of small or trace evidence.
Unbreakable plastic pill bottles with pressure lids
adequate containers for most trace evidence encountered at crime sites.
manila envelopes, screw-cap glass vials, or cardboard pillboxes
Ordinary mailing envelopes should not be used as evidence containers because
powders and fine particles will leak out of their corners.
Small amounts of trace evidence can also be conveniently packaged in
a carefully folded paper, using what is known as a "druggist fold.
Evidence from arson scenes should be packaged in
airtight metal or glass containers to prevent the loss of accelerant vapors.
If biological or bloodstained materials are stored in airtight containers,
the accumulation of moisture may encourage the growth of mold, which can destroy the evidential value.
In these instances, the material should be allowed to air-dry before being packaged in wrapping paper, manila envelopes, or paper bags.
Contamination is a key concern during the collection of
DNA-containing specimens such as blood, saliva, sweat or skin cells. Contamination can occur either by introducing foreign DNA through coughing or sneezing onto evidence or if items of evidence are incorrectly placed in contact with each other during pack
To prevent contamination, the evidence collector must wear
a face mask and lab coat, use disposable latex gloves and work with disposable forceps when collecting evidence that may contain DNA.
Disposable coveralls, shoe covers, and eye protection offer added precautions to avoid contaminating DNA evidence.
Chain of Custody
a list of all persons who came into possession of an item of evidence.
Continuity of possession, or the chain of custody, must be established whenever evidence is
presented in court as an exhibit.
Adherence to standard procedures in recording the location of evidence, marking it for identification, and
properly completing evidence submission forms for laboratory analysis is critical to
chain of custody.
This means that every person who handled or examined the evidence and where it is at all times must be accounted for.
Standard/Reference Sample
Physical evidence whose origin is known, such as blood or hair from a suspect, that can be compared to crime-scene evidence.
The examination of evidence, whether it is soil, blood, glass, hair, fibers, and so on, often requires
comparison with a known standard/reference sample.
Although most investigators have little difficulty recognizing and collecting relevant crime-scene evidence, few seem aware of the necessity and importance of
providing the crime lab with a thorough sampling of
standard/reference materials.
who decides when all pertinent physical evidence has been recorded and collected at the crime scene.
The experienced lead investigator
A final survey is undertaken to visually review the scene and collect all evidence and equipment.
Following the final survey, the crime scene is released to the proper authorities.
Evidence is usually submitted to the laboratory either by
personal delivery or by mail shipment.
Care must be taken in packaging evidence that will be sent by mail in order to
prevent breakage or other accidental destruction during transit to the laboratory.
Most laboratories require that _______ accompany all evidence submitted.
an evidence submission form
Case information provided on this form enables the laboratory analyst to make an intelligent and complete examination of the evidence.
Crime scenes frequently present the investigator with biological specimens of unknown origin;
the investigator has no way of gauging what health hazards
they may contain. One must use caution and protection at all times.
It is recommended that personnel always wear
latex gloves and possibly chemical resistant clothing, Tyvek-type shoe covers, a particle mask/respirator, goggles, or face shields when potentially infectious material is present. Gloves should be changed often.
Personnel should maintain a red biohazard plastic bag for the disposal of
contaminated gloves, clothing, masks, pencils, wrapping paper, and so on
When processing and collecting evidence at a crime scene, personnel should be alert to
sharp objects, knives, hypodermic syringes, razor blades, and similar items.
The removal of any evidence from a person or from the scene of a crime must be done in conformity with
Fourth Amendment privileges:
"The right of the people to be secure in their
persons, houses, papers, and effects, against
unreasonable searches and seizure, shall not
be violated, and no warrants shall issue, but
upon probable cause, supported by oath or
The United States Supreme Court has determined that search and seizure without a court-approved warrant is
justified in four cases:
1.) The existence of emergency circumstances
2.) The need to prevent the immediate loss or destruction of evidence
3.) A search of a person and property within the immediate control of the person provided it is made incident to a lawful arrest
4.) A searc
In the case of Mincey v. Arizona,
the Court dealt with the legality of a four-day search at a homicide scene and determined that the evidence was illegally seized because a warrant was never issued and the circumstances of the case did not justify a warrantless
search.
In Michigan v. Tyler,
fire destroyed a business establishment leased by Loren Tyler and a business partner. The court decided that evidence obtained from the initial search was legally seized, but evidence obtained from searches 4, 7, and 24 days after the incident were illega