Biological Evidence Past Paper PDF FOS 706 F20

FOS 706 Physical & Biological Evidence Introduction ■ FOS – Biological Evidence ■ FOS – 706 Overview of biological evidence 711 Biological Evidence & Serology ■ Molecular – PROFESSOR LINDA ROURKE – 1 2 IDENTIFICATION ■ Presumptive – – – – – REFINED IDENTIFICATION testing ■ Biological...

FOS 706 Physical & Biological Evidence Introduction ■ FOS – Biological Evidence ■ FOS – 706 Overview of biological evidence 711 Biological Evidence & Serology ■ Molecular – PROFESSOR LINDA ROURKE – 1 2 IDENTIFICATION ■ Presumptive – – – – – REFINED IDENTIFICATION testing ■ Biological Specificity: Screening tests Fast, sensitive tests, many of which can be done “at the scene” Decisions in evidence collection ■ Confirmatory – – Is the physiological fluid stain from a human? If not, then what species of animal is the source of the non-human bloodstain? ■ Species testing – Specificity: unequivocal identification of the biological material Frequently less sensitive and may be more time consuming 3 Testing What kind of markers can distinguish different animal species? 4 INDIVIDUALIZATION ■ Biological EVIDENCE IN CONTEXT Specificity : ■ INDIVIDUAL ITEMS IN ISOLATION ARE LESS INFORMATIVE ■ THINK BEYOND “TESTS” APPLIED TO “ITEMS” ■ WHAT CAN BE LEARNED FROM THE TOTALITY OF THE PHYS ICAL EVIDENCE? ■ SEEK THE “BIG PICTURE” Who is the source of the unknown biological evidence? – Traditional techniques: protein typing – Current techniques: DNA typing – 5 Biology Track Forensic DNA Analysis Concepts & Methods 6 1 EVIDENCE IN CONTEXT BIOLOGICAL EVIDENCE ■ Non-scientist ■ investigators may consider the test without reference to its applicability to answering pertinent questions. ■ The scientist is needed to ask the right questions with regard to evidence analysis. 7 PHYSIOLOGICAL FLUIDS – – ■ HAIRS – – ■ ■ Naturally Shed (Telogen) Pulled, Cut, and Damaged (Anagen/Catagen) SLOUGHED OFF EPITHELIAL CELLS TEETH & BONES 8 Physiological Fluids More Physiological Fluids… ■ Blood § ■ Seminal § fluid ■ Saliva § § ■ Urine § ■ Sweat § ■ Vaginal Secretions ■ Pus ■ Serum 9 § § tears milk blister exudate aqueous humor vitreous humor cerebrospinal fluid intercellular fluid mucous § § § § § § § § § gastric juice pancreatic juice bile lymph fecal matter vomit amniotic fluid sebaceous secretions cerumen § § § § § § § § § edema fluid synovial fluid pericardial fluid bone marrow fetal blood cord blood menstrual blood lochia sputum 10 Blood vs. Other Fluids Physiological Fluids Methods of analysis for blood are fairly well developed for forensic purposes: ■ Most common biological fluid analyzed as evidence. ■ Frequently encountered in crimes of assault, homicide, sexual assault. For other types of biological fluids, sophistication of methods vary. 11 Blood, Semen, Saliva, etc. Fluids vs. Stains Fluids with well developed analytical methods: ■ Blood ■ Menstrual blood – in addition to normal blood components, have vaginal epithelial cells and fibrinolysin ■ Seminal Fluid 12 2 Hair ■ Microscopical – Identification analysis ■ How can we unequivocally identify a particular physiological fluid? ■ Is it possible to unequivocally identify all of the aforementioned biological materials? Morphological characteristics ■ DNA – – Nuclear DNA from anagen hair roots Mitochondrial DNA within hair shaft – – 13 Context Relevance 14 Polymorphisms ■ POLYSACCHARIDES – – ■ ■ DNA RBC SURFACE ANTIGENS LEUCOCYTE SURFACE ANTIGENS – – PROTEINS (POLY AMINO ACIDS) – – ■ Polymorphisms ■ PROTEINS SERUM PROTEINS INTRA-RBC PROTEINS – – NUCLEIC ACIDS (POLY NUCLEOTIDES) – & POLYSACCHARIDES STRUCTURAL POLYMORPHISMS FUNCTIONALITY LEUCOCYTE NUCLEI (DNA and RNA) 15 16 Secretor Status Secretor Status ■A ■ The secretor can be defined as an individual whose body fluids contain large quantities of water soluble ABO agglutinogens. ■ About 80% of the population can be classified as secretors. ■ This trait is controlled genetically. ■ Shorthand notation for phenotypes: – – 17 LENGTH POLYMORPHISMS SEQUENCE POLYMORPHISMS secretor trait is dominant. notation for genotypes: ■ Shorthand – – – SeSe represents homozygous secretors Sese represents heterozygous secretors sese represents a non-secretor. Se is used to indicate a secretor. se is used to designate a non-secretor. 18 3 Secretor Status Mixed Stains ■ The secretor status is correlated with another cellular antigen system known as the Lewis system. – – – Sexual Assault Cases ■ Vaginal secretions + seminal fluid – Le(a-b+) individuals are secretors. Le(a+b-) individuals are non-secretors. Le(a-b-) persons can be either secretors or non-secretors. 19 – Differential extractions Y-STRs ■ Other mixtures consistent with sexual assault cases depending on the specificities of the sexual assault. ■ Blood + another physiological fluid 20 Mixed Stains Methods Other mixtures: ■ Blood from 2 or more sources ■ Blood + another physiological fluid ■ Physiological fluid stain + trace DNA from epithelial cells 21 ■ Protein – ■ Antibody/Antigen Interactions ■ Electrophoresis ■ ELISA ■ DNA/RNA Typing 22 Forensic Significance Of DNA u u u 23 Typing Immunological Tests Forensic Significance Of DNA Every human being is biologically unique because of the different sequences of DNA in their chromosomes. Since 99.5% is the same, we look at the 0.5% that makes us unique (eye color, hair color, etc…) Polymorphic proteins and varied repeat regions in noncoding DNA Þ a person can “essentially” be individualized based on their DNA. u u Exception: identical twins cannot be distinguished using current forensic DNA STR typing methods. But…. u u u Epigenomics may be able to distinguish identical twins! Methylation alters gene expression. Older identical twins can have different epigenome based on environmental factors (diet, career choice, lifestyle) 24 4 Distinguishing Identical Twins? https://www.dnaworldwide.com/blog/194/new -discovery-identical-twinsdont-have-identical-dna https://www.nytimes.c om/2019/03/01/scienc e/twins-dna-crimepaternity.html 25 26 Forensic Significance Of DNA Forensic Significance Of DNA Biological evidence containing DNA can link a suspect to a crime scene or victim: semen, blood, skin/tissue cells. u Forensic DNA analysis seeks to identify the source of the biological evidence. Biological evidence can easily be contaminated or destroyed. u Always collect controls for comparison. u The type, condition & quantity of biological material determine the kinds of DNA analyses which can be performed. u 27 u 28 Interpretations ■ Sensitivity: Limits of detection ■ Specificity ■ False ■ False Positives Negatives ■ Controls: quality assurance/quality control ■ Context relates to relevance 29 30 5 Crime Scene Issues Crime Scene Issues Common forms of evidence for DNA: Common sources of DNA: ■ ■ ■ ■ ■ ■ ■ ■ Blood Semen Saliva Urine Hair Teeth Bone Tissue ◆ ◆ ◆ ◆ ◆ ◆ ◆ Victim/Suspect Clothing Bedding Bitemarks Used condom Tissue under fingernails Smoked cigarette Pattern evidence: fingerprint http://www.cstl.nist.gov/biotech/strbase/ppt/intro.ppt 31 32 Crime Scene Issues Crime Scene Issues Documentation - visual and written u sketches u photography u long range, medium range, close up Contamination of Biological Samples u use gloves, change them often u avoid combining items: cross contamination u proper packaging u proper temperature u u before and after evidence collected photo log 33 35 34 Crime Scene Issues Evidence Preservation Collection of Controls u Substrate control u Victim/suspect controls u Other sources ■ Many factors in the environment can degrade DNA: Time Temperature Humidity (microorganisms) Light Chemical/environmental hazards ■ Ideal environment for preservation: Dry and frozen 36 6 Crime Scene Issues Low Copy Number DNA Destructive nature of DNA analysis Significance of preliminary screening of sample in the lab prior to DNA analysis u Microscopical examination u Photographic documentation of patterns ■ Also 37 known as touch DNA ■ DNA profiles can be obtained from a few skin cells ■ Requires more stringent amplification conditions ■ Secondary transfer of DNA is of concern 38 Familial DNA Forensic Genealogy Searching for the DNA source by looking for a relative whose DNA profile is in the CODIS database; used when the source DNA profile is NOT already in CODIS. https://www.nbcnews.com/news/us-news/golden-state-killer-case-ex-cop-arrested-serial-murderrape-n868936 39 40 ■ ■ ■ Forensic Genealogy Forensic Phenotyping DNA data from 23andMe and Ancestry.com can be uploaded to GEDmatch, a database used to search for relatives. Genealogists compile family trees using the DNA data and publicly available information. Investigators survey the family tree for potential suspects; ”discarded” DNA samples used to verify a match. ■ Using DNA from biological samples to assess the physical appearance of the DNA source; NOT DEFINITIVE – – – – – 41 Hair color Eye color Skin pigmentation Biogeographical ancestry Body type 42 7 DNA: Interpreting Data Case Examples Profiler Plus STR Alleles Detected Sample D3S1358 vWA FGA Fingernail Clipping #7R 14,15,18 15,17,19 18,22 Victim (QW) 14,15 17,19 18,22 Suspect (DC) 15,17 15,17 19,22 DC a contributor? no maybe no Alleles not from QW or DC 18 18 or 15 or Possible phenotypes of non- 14,18 or 15,17 or 18 or 22 QW contributor 15,18 15,19 or 18,22 AMEL X,Y X X,Y maybe Cofiler STR Alleles Detected Sample D3S1358 D16S539 Fingernail Clipping #7R 14,15,18 11 Victim (QW) 14,15 11 Suspect (DC) 15,17 9,13 DC a contributor? no no Alleles not from QW or DC 18 18 or Possible phenotypes of non- 14,18 or QW contributor 15,18 11 43 X,Y D8S1179 D21S11 D18S51 D5S818 D13S317 D7S820 13,14,15 28,29,30 17,18,21 8,12,13 11,12,13 8,10,11 15 28 17,18 13 11,12 8,10 14 28,29 17* 12,13 11,12 ND maybe maybe maybe maybe maybe ? 13 30 21 8 13 ? 13 or 30 or 21 or 13 or 11 or 13,14 or 28,30 or 17,21 or 8 or 8,12 11,13 or 8,11 or 13, 15 29,30 18,21 or 8,13 12,13 10,11 AMEL X,Y X X,Y maybe THO1 7,8,9.3 7,9.3 7,8 maybe TPOX 6,8 6,8 8,12 no CSF1PO 8,10,11 8,10 11 maybe D7S820 8,10,11 8,10 8,10 maybe X,Y 8 or 7,8 or 8,9.3 6 or 8 or 6,8 11 or 8,11 or 10,11 11 or 8,11 or 10,11 44 DNA False Positive 1999 UK case: man arrested based on 6 loci match to burglary scene sample ◆ ◆ 45 46 DNA False Positive? DNA False Negatives? UK Burglary Suspect ◆ ◆ ◆ ◆ ◆ 47 Suspect had advanced Parkinson’s disease, could not drive & lived 200 miles from burglary site Excluded and released after 10 loci testing performed at his lawyer’s request. 5 related burglaries Cigarette butt tested from each scene Odds of false match were 1 in 86 million (7 loci); 1 in 79,000 (5 loci) But if you consider the chance of a relative committing crime (suspect had 2 brothers, one had also been arrested then released) ◆ Odds change to 1 in 267 (7 loci) and 1 in 32 (5 loci) Issues of interpretation ◆ ◆ ◆ ◆ use of a condom multiple offenders Earlier/later consensual contact with another person Innocence Project: Kerry Kotler 48 8 LA Times Article: Romanov Family Identified ◆ ◆ Identification of Tsarina and 3 daughters by mtDNA Identification of Tsar: technical difficulties (heteroplasmy); recent exhumation of his brother confirms ID From http://www.solvethecrime.co.uk/forensic/news/casefiles/roman.htm u 49 Anna Anderson is not Anastasia. 50 Conclusions ◆ ◆ DNA is an incredibly powerful tool in forensic science but it cannot supplant other areas of evidential analysis. All areas of forensic evidence analysis require careful interpretation. 51 9