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Forensic Science Unit D: Summary.

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1 Forensic Science Unit D: Summary

2 Forensic Engineering Concerned with:
Failure analysis Accident reconstruction Cause and origin of fires or explosions Answer questions such as how did an accident occur or what structural failure occurred

3 Forensic Pathology Involves the investigation of sudden, unnatural, unexplained, or violent deaths. Typically these are the medical examiners or coroners Answer questions: who is the victim, what injuries are present, when did the injuries occur, why and how were the injuries produced, and what is the cause of death

4 Criminalist (CSI) Analyzes, compares, identifies, & interprets physical evidence at crime scenes. Criminalists examine and identify physical evidence to reconstruct a crime scene. Physical evidence can be a weapon, a piece of clothing, a bloodstain, drugs, or even a vapor in the air. Criminalists use physical evidence to provide a connection between the suspect and the victim. Such connections are acquired by the transfer of hair or clothing fibers from a suspect to the victim. Other connecting links are fingerprints, bullets, or shoe impressions. Physical evidence is collected from a crime scene that includes the victim's body and the surrounding area of the crime.

5 Forensic Anthropology
Identification and examination of human skeletal remains Trying to determine origin, sex, approximate age, race and skeletal injury May create facial reconstruction Identify victims of mass disaster such as plane crash

6 Forensic Toxicologist
Analyses alcohol, drugs, & poisons in body fluids for the benefit of the courts. Forensic toxicology is essentially a specialty area of analytical chemistry which specifically looks at body fluids for presence of drugs, poisons, and/or alcohol.

7 Manner of Death Natural: Homicide Suicide Accidental Undetermined

8 Cause of Death Asphyxiation Exsanguination Blunt force trauma
Strangulation Drowning Fire victim Exsanguination Major blood loss Blunt force trauma Sharp force trauma Chemical trauma

9 Estimated Time of Death
Autopsy Rigor Mortis: the stiffening of body parts in the position they are in when death occurs. Lividity: medical condition that occurs after death and results in the settling of blood in areas of the body closest to the ground Body Temp: postmortem changes that cause a body to lose heat o C/hr

10 Estimated Time of Death
Livor Mortis or lividity: medical condition that occurs after death and results in the settling of blood in areas of the body closest to the ground. Begins immediately after death and lasts for 12 hours Algor Mortis: postmortem changes that cause a body to lose heat. Process in which the body continues to cool to room temperature. 1 – 1.5 degree/hour

11 Forensic Entomology Study of insects and their relation to a criminal investigation After decomposition begins, insects such as blow flies are the first to infest the body

12 Arriving at the Crime Scene
Secure and isolate the crime scene Determine boundaries of crime scene and priorities for evidence collection Rough sketch Finished sketch Photograph Videotaping Notes

13 Collecting Evidence Conduct a systematic search for evidence; be unabiased and thorough. Field technicians What to look for depends on the crime and what specific locations of the crime scene would most likely be affected Microscopic or massive objects Collect carriers of possible evidence Vacuum or sweeping collected

14 Packaging of Evidence Prevent any changes from occurring (contamination, breakage, evaporation, bending, loss) Process trace evidence from original object (shirt, shoe) rather than isolating and packaging if possible Package evidence separately

15 Chain of custody Continuity of possession; every person who touched it must be accounted for Standards for collecting, labeling, and submitting evidence forms are necessary for court Labels include collectors initials, location of evidence, date of collection. Identification numbers must also be used

16 Submission of Evidence
Standard/reference samples Substance controls Evidence submission form will detail the evidence collect and particular type of examination/analysis requested. Lab tech not bound by requests

17 Methods of Detection Types of prints
Latent print Visible print – deposited ink, blood, dirt Plastic print – impression in a soft surface Most natural finger prints consists of secretions of the skin’s glands Developed by either powders or chemicals

18 Fingerprints History 3 Patterns
Japanese used thumb print as a signature on documents until 1860. First used in crime in 1901 by Sir Edward Richard Henry 3 Patterns Whorl Loop Arch

19 Categories of Fingerprints
Loop – ridge lines enter one side of pattern and curve around to exit from the same side of pattern. (65%) Whorl – ridge lines rounded or circular and have two deltas(30-35%) Arch – ridge lines enter print from one side and exit from the other (5%)

20 Blood Evidence Serology: the study of antigen – antibody reactions using laboratory tests Kastle-Myer Test – Is it blood? Precipitin Test – Is it human blood? DNA Analysis – Whose blood is it?

21 ABO blood typing RBCs have A, B, neither, or both antigens in its surface. Serum carries antibodies against antigens it does not have. O negative carries no Ag and therefore does not react with any Anti A, B, AB. Rh factor is a separate protein on the surface of RBCs Pos reaction Neg reaction

22 Blood Splatter Analysis
Location, distribution, and appearance of blood stains are an important part of forensics Investigators try to determine: Direction Dropping distance Angle of impact Splatter analysis is often used for crime scene reconstruction

23 Blood Splatter Analysis
Factors which influence stain patterns are: Surface texture Direction of travel Pointed end of bloodstain always faces its direction of travel Angle of impact is determined by measuring the degree of circular distortion of the stain Blood striking a surface at right angles gives rise to a nearly circular stain As the angle decreases, the stain becomes elongated in shape

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