Forensic Science Unit D: Summary. Forensic Engineering Concerned with: Concerned with: –Failure...
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Transcript of Forensic Science Unit D: Summary. Forensic Engineering Concerned with: Concerned with: –Failure...
Forensic Science Forensic Science
Unit D: SummaryUnit D: Summary
Forensic EngineeringForensic Engineering
Concerned with:Concerned with:– Failure analysisFailure analysis– Accident reconstructionAccident reconstruction– Cause and origin of fires or explosionsCause and origin of fires or explosions
Answer questions such as how did an Answer questions such as how did an accident occur or what structural accident occur or what structural failure occurredfailure occurred
Forensic PathologyForensic Pathology
Involves the investigation of sudden, Involves the investigation of sudden, unnatural, unexplained, or violent unnatural, unexplained, or violent deaths.deaths.– Typically these are the medical examiners or Typically these are the medical examiners or
coronerscoroners Answer questions: who is the victim, Answer questions: who is the victim,
what injuries are present, when did the what injuries are present, when did the injuries occur, why and how were the injuries occur, why and how were the injuries produced, and what is the cause injuries produced, and what is the cause of deathof death
Criminalist (CSI)Criminalist (CSI)Analyzes, compares, identifies, & interprets Analyzes, compares, identifies, & interprets
physical evidence at crime scenes.physical evidence at crime scenes.
Forensic AnthropologyForensic Anthropology
Identification and examination of Identification and examination of human skeletal remainshuman skeletal remains– Trying to determine origin, sex, Trying to determine origin, sex,
approximate age, race and skeletal approximate age, race and skeletal injuryinjury
– May create facial reconstructionMay create facial reconstruction– Identify victims of mass disaster such as Identify victims of mass disaster such as
plane crashplane crash
Forensic ToxicologistForensic Toxicologist
Analyses alcohol, drugs, & poisons in body Analyses alcohol, drugs, & poisons in body fluids for the benefit of the courts.fluids for the benefit of the courts.
Manner of DeathManner of Death
Natural:Natural: HomicideHomicide SuicideSuicide AccidentalAccidental UndeterminedUndetermined
Cause of DeathCause of Death
AsphyxiationAsphyxiation– StrangulationStrangulation– DrowningDrowning– Fire victimFire victim
ExsanguinationExsanguination– Major blood loss Major blood loss
Blunt force traumaBlunt force trauma Sharp force traumaSharp force trauma Chemical traumaChemical trauma
Estimated Time of DeathEstimated Time of Death
AutopsyAutopsy Rigor Mortis: the stiffening of body parts in Rigor Mortis: the stiffening of body parts in
the position they are in when death occurs. the position they are in when death occurs. Lividity: medical condition that occurs after Lividity: medical condition that occurs after
death and results in the settling of blood in death and results in the settling of blood in areas of the body closest to the groundareas of the body closest to the ground
Body Temp: postmortem changes that Body Temp: postmortem changes that cause a body to lose heat. 1-1.5cause a body to lose heat. 1-1.5oo C/hr C/hr
Estimated Time of DeathEstimated Time of Death
Livor Mortis or lividity: medical condition Livor Mortis or lividity: medical condition that occurs after death and results in the that occurs after death and results in the settling of blood in areas of the body settling of blood in areas of the body closest to the ground. Begins closest to the ground. Begins immediately after death and lasts for 12 immediately after death and lasts for 12 hourshours
Algor Mortis: postmortem changes that Algor Mortis: postmortem changes that cause a body to lose heat. Process in cause a body to lose heat. Process in which the body continues to cool to room which the body continues to cool to room temperature. 1 – 1.5 degree/hourtemperature. 1 – 1.5 degree/hour
Forensic EntomologyForensic Entomology
Study of insects Study of insects and their relation to and their relation to a criminal a criminal investigationinvestigation
After decomposition After decomposition begins, insects such begins, insects such as blow flies are the as blow flies are the first to infest the first to infest the bodybody
Arriving at the Crime SceneArriving at the Crime Scene
Secure and isolate the crime sceneSecure and isolate the crime scene Determine boundaries of crime scene Determine boundaries of crime scene
and priorities for evidence collectionand priorities for evidence collection Rough sketch Rough sketch Finished sketchFinished sketch Photograph Photograph Videotaping Videotaping NotesNotes
Collecting EvidenceCollecting Evidence
Conduct a systematic search for Conduct a systematic search for evidence; be unabiased and thorough.evidence; be unabiased and thorough.
Field techniciansField technicians What to look for depends on the crime What to look for depends on the crime
and what specific locations of the crime and what specific locations of the crime scene would most likely be affectedscene would most likely be affected
Microscopic or massive objectsMicroscopic or massive objects Collect carriers of possible evidenceCollect carriers of possible evidence Vacuum or sweeping collectedVacuum or sweeping collected
Packaging of EvidencePackaging of Evidence
Prevent any changes from occurring Prevent any changes from occurring (contamination, breakage, (contamination, breakage, evaporation, bending, loss)evaporation, bending, loss)
Process trace evidence from original Process trace evidence from original object (shirt, shoe) rather than object (shirt, shoe) rather than isolating and packaging if possibleisolating and packaging if possible
Package evidence separatelyPackage evidence separately
Chain of custodyChain of custody
Continuity of possession; every person Continuity of possession; every person who touched it must be accounted forwho touched it must be accounted for
Standards for collecting, labeling, and Standards for collecting, labeling, and submitting evidence forms are submitting evidence forms are necessary for court necessary for court
Labels include collectors initials, Labels include collectors initials, location of evidence, date of collection. location of evidence, date of collection. Identification numbers must also be Identification numbers must also be usedused
Submission of EvidenceSubmission of Evidence
Standard/reference samplesStandard/reference samples Substance controlsSubstance controls Evidence submission form will detail Evidence submission form will detail
the evidence collect and particular the evidence collect and particular type of examination/analysis type of examination/analysis requested. requested.
Lab tech not bound by requestsLab tech not bound by requests
Methods of DetectionMethods of Detection
Types of printsTypes of prints– Latent printLatent print– Visible print – deposited ink, blood, dirtVisible print – deposited ink, blood, dirt– Plastic print – impression in a soft surfacePlastic print – impression in a soft surface
Most natural finger prints consists of Most natural finger prints consists of secretions of the skin’s glandssecretions of the skin’s glands
Developed by either powders or Developed by either powders or chemicalschemicals
FingerprintsFingerprints HistoryHistory
– Japanese used thumb print as a Japanese used thumb print as a signature on documents until 1860.signature on documents until 1860.
– First used in crime in 1901 by Sir First used in crime in 1901 by Sir Edward Richard HenryEdward Richard Henry
3 Patterns3 Patterns– WhorlWhorl– LoopLoop– ArchArch
Categories of FingerprintsCategories of Fingerprints
Loop – ridge lines enter one side of Loop – ridge lines enter one side of pattern and curve around to exit pattern and curve around to exit from the same side of pattern. (65%)from the same side of pattern. (65%)
Whorl – ridge lines rounded or Whorl – ridge lines rounded or circular and have two deltas(30-35%)circular and have two deltas(30-35%)
Arch – ridge lines enter print from Arch – ridge lines enter print from one side and exit from the other one side and exit from the other (5%)(5%)
Blood EvidenceBlood Evidence
SerologySerology: the study of antigen – : the study of antigen – antibody reactions using laboratory antibody reactions using laboratory teststests
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?
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
Blood Splatter AnalysisBlood Splatter Analysis
Location, distribution, and appearance Location, distribution, and appearance of blood stains are an important part of blood stains are an important part of forensicsof forensics
Investigators try to determine:Investigators try to determine:– DirectionDirection– Dropping distanceDropping distance– Angle of impactAngle of impact
Splatter analysis is often used for Splatter analysis is often used for crime scene reconstructioncrime scene reconstruction
Blood Splatter AnalysisBlood Splatter Analysis
Factors which influence stain patterns are:Factors which influence stain patterns are:– Surface textureSurface texture– Direction of travelDirection of travel
Pointed end of bloodstain always faces its direction Pointed end of bloodstain always faces its direction of travelof travel
– Angle of impactAngle of impact is determined by measuring is determined by measuring the degree of circular distortion of the stainthe degree of circular distortion of the stain Blood striking a surface at right angles gives rise to Blood striking a surface at right angles gives rise to
a nearly circular staina nearly circular stain As the angle decreases, the stain becomes As the angle decreases, the stain becomes
elongated in shapeelongated in shape