Chapter 1: Forensic Biology

 Common Disciplines:  Crime scene investigation  Latent print examination  Forensic Biology  Controlled substance analysis  Postmortem toxicology  Questioned document examination  Firearms, toolmark, and other impression evidence examination  Explosives and fire debris examination  Transfer (Trace) evidence examination 2Forensic Biology by Richard Li

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 Forensic Pathology  Autopsies used to determine exact cause of death  Time of death  Manner of death: ▪ Natural ▪ Homicide ▪ Suicide ▪ Accident ▪ Undetermined 9

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 Forensic Anthropology  Identification and examination of human skeletal remains  Examination may reveal: ▪ Individual’s origin ▪ Sex ▪ Approximate age ▪ Race ▪ Presence of skeletal injuries 12

 Forensic Entomology  The study of insects in relation to a criminal investigation  Estimating time of death ▪ Stages of insect development 13

 Forensic Odontology  Participate in the identification of victims whose bodies are unrecognizable  Use characteristics of teeth, alignment, and overall structure  Bite mark analysis 14

 History  Antigen polymorphism  Protein polymorphism  DNA polymorphism 15

 Antigen Polymorphism  1900 Karl Landsteiner discovered ABO blood groups  A, B, AB, O  Forensic serology  Useful in excluding a suspect 16

 Protein polymorphism  By 1980 approximately 100 had been discovered  Combined with blood groups lowered the probability of a match between two unrelated individuals 17

 DNA polymorphism  1984 Sir Alec Jeffreys ▪ Variable Number Tandem Repeat (VNTR) ▪ Used in 1986 to solve murder case in the United Kingdom  Able to reveal far greater individual variability  The probability of two unrelated individuals having the same DNA profile is low  DNA from crime scene can be matched to a suspect 18

 DNA polymorphism  Mid 1980’s Polymerase Chain Reaction (PCR) technique ▪ Amplifies tiny quantities of DNA ▪ Greatly increased the sensitivity of forensic DNA ▪ Single Nucleotide Polymorphisms (SNP) ▪ Amplified Length Polymorphisms (AFLP) ▪ Short Tandem Repeat (STR) ▪ Greatly increased the sensitivity of the assay ▪ Highly variable 19

 DNA polymorphism  First national DNA database for criminal investigations established in the United Kingdom  First in United States ▪ Combined DNA Index System (CODIS) ▪ 13 STR loci  Mitochondrial DNA (mtDNA) ▪ Maternally inherited ▪ Useful when nuclear DNA is degraded or in limited amounts ▪ E.g. shed hairs  Polymorphic markers at the Y chromosome ▪ Paternally inherited ▪ Paternity cases ▪ Multiple contributors in sexual assault cases 20