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