forensic for sci - boun.edu.tr · 10/04/2014 5 criminalistics by richard saferstein prentice hall...
TRANSCRIPT
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INTRODUCTION TO FORENSIC SCIENCE
N. Zeynep Atay Department of Chemistry
What is Forensic Science
It is the application of Science to Criminal and Civil Laws
HISTORY OF FORENSIC SCIENCE
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CRIME SCENE Forensic Science begins at the crime scene.
Finished-sketch diagram of a crime scene. Courtesy Sirchie Finger Print Laboratories, Inc., Youngsville, N.C., www.sirchie.com.
Criminalistics by Richard Saferstein
Prentice Hall
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MODERN CRIME LABORATORIES
CRIME LABORATORIES AND THEIR ORGANIZATION
SERVICES OF THE CRIME LABORATORY
Physical Science Unit Biology Unit Firearms Unit Document Examination Unit Photography Unit
OPTIONAL SERVICES PROVIDED BY FULL-SERVICE CRIME LABORATORIES
Toxicology Unit Fingerprint Unit Polygraph Unit Lie-detector
Voiceprint Analysis Unit Crime-Scene Investigation (CSI) Unit
FUNCTIONS OF THE FORENSIC SCIENTIST
Analysis of physical evidence Expert Witness Training of staff in the proper recognition,
collection, and preservation of physical evidence
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OTHER FORENSIC SCIENCE SERVICES
Forensic Pathology Forensic Anthropology Forensic Psychiatry Forensic Odontology Forensic Engineering Forensic Computer and Digital Analysis
Forensic Pathology
Involves the investigation of sudden, unnatural, unexplained or violent deaths by either observation or through an autopsy.
By investigating the stages of decomposition
of the body, time of death can be estimated.
Forensic Anthropology
Involves mainly the identification and examination of human skeletal remains.
Examination of bones may reveal sex, approximate
age, race and skeletal injury. Especially helpful identifying victims of a mass
disaster, such as a plane crash, through the collection of bone fragments.
Forensic Entomology
Study of insects and their relationship to criminal investigation.
After decomposition begins, insects such as blowflies
start infesting the body, laying their eggs in human remains, and ultimately hatch into maggots, etc.
Entomologists can identify these insects and
approximate how long the body has been left exposed by examining the stages of fly larvae.
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Criminalistics by Richard Saferstein Prentice Hall
Forensic Psychiatry
A specialised area which investigates the human behaviour and legal proceedings.
For civil cases, they determine whether the person is competent to make decisions on wills, etc.
For criminal cases, they evaluate behavioral
disordersand determine competence to stand trial.
Forensic Odontology
Helps identify victims through dental remains when the body is in unrecognizable state.
Teeth are composed of enamel, the hardest substance in the body. Due to the resilience of enamel, the teeth outlasts tissues and organs as decomposition begins.
Dental records can be compared to the suspected victim.
Bite-mark analysis is also important in identifying the suspect.
Forensic Engineering
Accident scenes are examined, photographs are reviewed, mechanical objects are investigated.
How did an accident or failure happen? Were the parties involved responsible? If yes, how were they responsible?
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Forensic Computer and Digital Analysis
A new and fast growing field that involves identification, collection, preservation and examination of information derived from computers and other digital devices such as mobile phones.
PHYSICAL EVIDENCE
“Physical Evidence can provide a link between a crime and its victim or a
crime and its perpetrator”
Common Types of Physical Evidence
Blood, Semen and Saliva – these are subject to serological and biochemical analysis (all contain DNA)
Documents – any handwriting, typewriting, ink, indented writing, obliterations, burned or charred documents (letters and e-mails link people)
Explosives – any device with an explosive charge and any item that might contain the explosive residue
A fingerprint exhibit illustrating the matching ridge characteristics between the crime-scene print and an inked impression of one of the suspect’s fingers. Courtesy New Jersey State Police.
Fingerprints (a classic identifier)
Criminalistics by Richard Saferstein Prentice Hall
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Friction Ridges Every person has minute raised ridges of skin on the inside surfaces of their hands and fingers and on the bottom surfaces of their feet and toes, known as 'friction ridge skin'.
The friction ridges provide a gripping surface - in much the same way that the tread pattern of a car tyre does.
Friction ridge skin is also the only skin on the body without hairs. Fingerprint ridge characteristics.
(Courtesy Sirchie Finger Print Laboratories, Inc., Youngsville, N.C., www.sirchie.com.)
Fingerprint Ridge Characteristics
150 different ridge characteristics = minutiae (trivial details)
How many fingerprint points must match in order for the fingerprints to be said to be identical?
UK → 16 pts. New Zealand and Australia → 12 pts. India → 8 pts. USA → each state has its own standard
FBI uses 12 pts. There is really no scientific basis on how
many points should be matched!!!!
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The Principles of Fingerprint Identification
Uniqueness: No two friction ridge patterns are identical, whether they are on
different fingers of the same person or on the fingers of different people. (The same principle covers all friction ridge skin.)
While this principle is difficult to prove empirically, no two fingerprints have ever been found to be identical in over a century of the use of fingerprinting.
Friction ridge patterns do not change naturally during the life of a person.
The pattern of minutiae starts developing in the third month of pregnancy and is fully formed by the fourth month.
During a person's lifetime, the pattern remains the same, apart from changing in size or by accident, mutilation or skin disease, until death.
In fact, the friction ridge patterns will remain after death until the body decomposes.
Additionally, studies have demonstrated that while identical twins share the
same DNA profile markers, they can nevertheless be differentiated by their fingerprints.
POWDERS
Powder And Tape – Probably the most well-known method of detecting latent prints is dusting for them. A variety of powders are used in dusting for prints, many containing aluminium or carbon. This finely crushed powder is gently applied to a surface, and the minute particles of powder cling to the print residue, making it visible to the human eye. These prints are then lifted using adhesive tape.
Brush it with aluminum powder The marks became visible.
Put a black rubber lifter on it.
The marks are on the lifter.
Put a plastic sheet over it. Ready to search!
Drugs
Marijuana
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Ice-methamphetamine
Fibers – any fiber that might show cross-transfer between object and/or persons (can link suspect and crime scene)
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In humans, pigment granules are commonly distributed toward the cuticle as shown in top figure, except in red-haired individuals as in bottom figure.
Hair – animal or human hair showing cross-transfer (hair can be matched microscopically)
Forensic Science CommunicationsJuly 2004 – Volume 6 – Number 3
Animal hairs have the pigment granules commonly distributed toward the medulla, as shown in the figure.
DOG HAIR
CAT HAIR
Forensic Science CommunicationsJuly 2004 – Volume 6 – Number 3
Photomicrograph of Human Hair Root
The root of human hairs is commonly club-shaped, whereas the roots of animal hairs are highly variable between animals.
Forensic Science CommunicationsJuly 2004 – Volume 6 – Number 3
Wineglass-shaped root (deer family)
Forensic Science CommunicationsJuly 2004 – Volume 6 – Number 3
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UNLESS DNA analyses are carried out:
Body area from which the hair originated: Scalp hair:
little variation in diameter Uniform pigment distribution Might be dyed Pubic hair: Short and curly Variable cross-section diameter Continuous medullae Beard hair: Coarse Triangular cross-section Blunt (not sharp) tips from shaving and cutting
Class Evidence: Hair
UNLESS DNA analyses are carried out: Age:
Age of an individual cannot be learned with any certainty except for infant (baby) hair.
Infant hair: Short Undeveloped in character
Sex: Hair gives no indication of the sex of the individual from which it came.
Glass
Particles that may show cross-transfer or panes that might have bullet holes (fragments are easy to compare)
Two bullet holes in a piece of glass. The left hole preceded the right hole
Criminalistics by Richard Saferstein Prentice Hall
Common Types of Physical Evidence (continued)
Firearms and Ammunition – discharged or
intact Impressions – tire markings, shoe prints,
depression in soil, glove or fabric impressions, bite marks in skin or food, as well as knife cuts
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Purpose of the Examination of Physical Evidence
Identification: Determination of the physical or chemical identity of a substance with as near absolute certainty as existing analytical techniques will allow.
Comparison: Subjecting a suspect specimen and a control specimen top the same tests for the ultimate purpose of proving common origin.
(Comparing two or more samples to see they match.)
Identification: Typical tests for identification: Drug analysis Species determination Explosive residue analysis
Drugs: Testing the composition of a white powder may show that it is illicit or prescription drug. Scientists need to determine what type of drug it is: heroin, cocain or barbiturates, or a commonly used drug!
Fibers: In case of suspected arson, fragments of cloth, found where the fire officers believe the fire might have started, could have petrol residues lingering in the fabric.
Comparison:
If any of the selected properties are not alike, the scientist will declare that the two items are not from the same source.
However, if all the selected properties match, they still may not be
able to conclude that the two specimens are from the same source with 100% accuracary.
Hence, usually only the probability that two specimens came from
the same source is given.
Characteristics of Physical Evidence
Individual: Associated with a “single source” with extremely high probability
Examples: Fingerprints Bullet Striations Footprints DNA
Class: Associated with a “class” with high probability, but associated with a “single source” with low probability.
Information can be gained by looking at the “class” of an item.
Example: Hair Blood type (O, A, B, AB)
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Class Evidence: Hair
Body area from which the hair originated: Scalp hair:
little variation in diameter Uniform pigment distribution Might be dyed Pubic hair: Short and curly Variable cross-section diameter Continuous medullae Beard hair: Coarse Triangular cross-section Blunt (not sharp) tips from shaving and cutting
Class Evidence: Hair
Age: Age of an individual cannot be learned with any
certainty except for infant (baby) hair. Infant hair:
Short Undeveloped in character
Sex: Hair gives no indication of the sex of the individual from which it came.
The probability of 2 people having the same fingerprint is 1 in 1x1060
Sources of Biological Evidence
Blood Semen Saliva Urine Hair Teeth Bone Tissue
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Most are rape cases (>2 out of 3) Looking for match between evidence and
suspect Must compare victim’s DNA profile
• Mixtures must be resolved
• DNA is often degraded
• Inhibitors to PCR are often present
Challenges
DNA Use in Forensic Cases Human Identity Testing
Forensic cases -- matching suspect with evidence Paternity testing -- identifying father Historical investigations Missing persons investigations Mass disasters -- putting pieces back together Convicted criminal DNA databases
CODIS
CODIS (Combined DNA Index System) is a computer software program developed by the FBI that maintains local, state, and national databases of DNA profiles from convicted offenders, unsolved crime scene evidence, and profiles of missing persons.
Thank you for your attention!