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Forensic Science Unit D: Summary. Forensic Engineering Concerned with: Concerned with: –Failure analysis –Accident reconstruction –Cause and origin of.

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Presentation on theme: "Forensic Science Unit D: Summary. Forensic Engineering Concerned with: Concerned with: –Failure analysis –Accident reconstruction –Cause and origin of."— Presentation transcript:

1 Forensic Science Unit D: Summary

2 Forensic Engineering Concerned with: 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 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. 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 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.

5 Forensic Anthropology Identification and examination of human skeletal remains 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.

7 Manner of Death Natural: Natural: Homicide Homicide Suicide Suicide Accidental Accidental Undetermined Undetermined

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

9 Estimated Time of Death Autopsy Autopsy Rigor Mortis: the stiffening of body parts in the position they are in when death occurs. 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 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 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 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 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 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 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 Secure and isolate the crime scene Determine boundaries of crime scene and priorities for evidence collection Determine boundaries of crime scene and priorities for evidence collection Rough sketch Rough sketch Finished sketch Finished sketch Photograph Photograph Videotaping Videotaping Notes Notes

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

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

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

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

17 Methods of Detection Types of prints 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 Most natural finger prints consists of secretions of the skin’s glands Developed by either powders or chemicals Developed by either powders or chemicals

18 Fingerprints History History –Japanese used thumb print as a signature on documents until –First used in crime in 1901 by Sir Edward Richard Henry 3 Patterns 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%) 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%) 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%) 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 Serology: the study of antigen – antibody reactions using laboratory tests Kastle-Myer Test – Is it blood? Kastle-Myer Test – Is it blood? Precipitin Test – Is it human blood? Precipitin Test – Is it human blood? DNA Analysis – Whose blood is it? 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 Neg reaction Pos reaction

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

23 Blood Splatter Analysis Factors which influence stain patterns are: 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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