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Forensic Science.

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Presentation on theme: "Forensic Science."— Presentation transcript:

1 Forensic Science

2 What is Forensic Science?
Forensic comes from the Latin word forensis. Meaning - for public discussion or debate. Any science, used for the purposes of the law, is a forensic science.

3 Forensic Scientists Television enhances the image of forensic science.
Forensic scientists are not involved in all aspects of criminal cases. Goal - use all available scientific information to determine the facts &, subsequently, the truth.

4 Forensic Scientists Scientific facts
Based on investigation, not circumstantial evidence or the sometimes unreliable testimony of witnesses. Forensic scientists can prove the existence of a crime or make connections to a crime.

5 Works Closely With State & Local Police & Sheriff
Prosecuting and Defense Attorneys Immigration workers Crime scene investigators DEA – Drug Enforcement Agency CIA – Central Intelligence Agency FBI – Federal Bureau of Investigation

6 Types of Forensic Scientists
Criminalistics   - Engineering   - General   - Jurisprudence    - Odontology    - Pathology/Biology    - Physical Anthropology   - Psychiatry & Behavioral Science    - Questioned Documents    - Toxicology

7 Locard Exchange Principle
Locard: director of the very first crime laboratory in Lyon, France. Principle states that "with contact between two items, there will be an exchange Perpetrator(s) of a crime comes into contact with the scene, they will both bring something into the scene and leave with something from the scene. Every contact leaves a trace.

8 Eight Forensic Techniques
Firearms and Tool Marks Forensic Profiling Document Examination Autopsy DNA Typing Forensic Anthropology Odontology Blood

9 Firearms and Tool Marks
Matching bullets to the gun that fired them. Tool Marks: ID characteristics between tools and the object it was used on Pry bar and door with matching imprints Explosives and imprint evidence.

10 Firearms Gunshot residue particle analysis pertains to:
Identification of bullet holes Estimation of range of fire Linking the suspect with the firing of a gun-in-question

11 Forensic Profiling Specially trained psychiatrist or investigator can examine crime scenes to develop a personality profile of the offender. Sex Age Occupation Lifestyle  

12 Document Examination This discipline involves relationships that between document and inscription and how it relates to a person or sequence of events. Forgery Counterfeiting Handwriting analysis.

13 Document Investigation
Document examination case fall into the "white-collar crime" category Include identity theft, forgery, counterfeiting, fraud, Questioned documents are often important in so many different contexts and for so many different purposes. May commit murder and forge a suicide note Document being produced directly as a part of a crime

14 Autopsy Post mortem exam determines: Manner of Death Method of Death
Time of Death Place of Death

15 Death That Must be Reported & Investigated
Sudden or unexpected Suspicious circumstances Result of an injury of Accident Natural death – disease or old age; Unnatural death – unexpected or unnatural causes

16 Other Reasons for Autopsy
Diagnosis Disease Evaluate possible public health issue For example, the diagnosis of Alzheimer’s disease can only be confirmed upon autopsy

17 Autopsy Process Includes external exam and photos
Tattoos, Scars, Birthmarks, etc. Followed by extensive internal exam: Organs are removed, weighed and examined Tissues and fluids are analyzed for abnormalities & presence of drugs

18 Fluids Examined Urine Semen Vomit Blood Stomach Contents Spinal Fluid

19 Medical Examiner Has the legal authority to order an autopsy without the consent of the deceased person’s next of kin. If not ordered by Medical Examiner, MUST have permission from next of kin.

20 DNA Typing What is DNA? Nucleus of cells contain RNA/DNA
DNA has deoxyribonucleic acid. Nucleus has 23 pairs of chromosomes made up of DNA In each pair, one chromosome from sperm, one from egg

21 DNA Typing Deoxyribonucleic acid (DNA) is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses. The main role of DNA molecules is the long-term storage of information.

22 DNA Typing What makes DNA individual? Four chemicals: Adenine Guanine
Cytosine Thymine.

23 DNA Typing DNA is often compared to a set of blueprints or a recipe, or a code Contains the instructions needed to construct other components of cells, such as proteins and RNA molecules.


25 DNA Typing Such examination can establish whether a given strand
is a strand of mammalian hair (vs. a synthetic or natural fiber), is a strand of human hair Is from the head or another region (pubic) Was a living, growing hair at the time it was separated Came from a particular race of persons

26 DNA Typing Chemical strung together = DNA code.
DNA varies from individual to individual Can link a strand of DNA to a given individual.

27 DNA Typing Where DNA is Found at the crime scene
Specimens – blood, hair, bloodstained clothing Provides powerfully compelling evidence Look in the Bathroom

28 Forensic Anthropology Examination of Skeletal Remains
Total Bones in body, 206, Missing Bones? Man 12 lbs Women 10 lbs Gender Male or Female: Pelvic Girth Race: To Some Extent Height: Ratio of Length of Long Bones to Height

29 Forensic Anthropology
Age at Time of Death: Size of Bones, Closure of Epiphysis Cause of Death or Lifestyle: Wear and Tear, Disease Processes (arthritis, fractures) How a person lived; Debilitating illnesses (rickets, polio, healed fractures); Right or left handedness Clues to occupation

30 Odontology Examination of Teeth
No other body part lasts longer In fires, often the only thing remaining No two people have identical teeth Dental records are needed to compare to the evidence Teeth can determine a subject’s age

31 Odontology WEST WARWICK, R.I., Feb 22, 2003
Fire investigators have recovered the remains of 96 victims of a Rhode Island nightclub and were working with forensic pathologists to aid identification efforts, 9 of the victims had been identified so far through dental records.



34 Blood - Serology Blood type – 4 types O, A, B, AB Rh Factor
Female cells have Barr Body

35 Blood Groups Blood Group Antigens Antibodies Can Give To
Can Receive From AB A & B None AB, A, B, O A B A & AB A & O B & AB B & O O

36 Blood Kastte - Meyer Test can determine if substance (stains) is really blood Precipiton Test determines if it is animal or human blood Determine gender from blood evidence – female cells have Barr body

37 Determining Time of Death Rigor Mortis
Begins 3 hours after death in face & eyelid muscles Takes 12 hours to affect entire body Process reverses after 36 hours. Rigor Mortis – Nysten’s Law: Rigor mortis affects first the muscle of the head and spreads toward the feet.

38 Determining Time of Death Lividity - Hypostasis
Visible 30 – 60 minutes after death Red cells settle & skin below turns red After 6 – 10 hours, color becomes permanent

39 Determining Time of Death Body Temperature
Falls at the rate of 1 degree per hour Obesity and warm environment slows cooling None of these are totally reliable and can be manipulated

40 Forensic Entomologists
Forensic entomologists work in classrooms, research labs & in the field. Practice of studying insects has existed for centuries, but there are so many areas of the field that remain largely untapped and promising. If body has been moved How long the body has been there


42 Eyewitness Accounts It used to be thought that memories were kind of like video tapes, but we now understand that all memories are reconstructions of events. Memory is very plastic and malleable Memories are often manipulated and greatly affected by our emotional state, personal prejudices and biases.


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