CRIM 355

  1. Forensic Biology
    • Biological material--> Blood, semen, saliva, hair, tissue, etc
    • Is it human?
    • Can it be individualized?
    • In past-mostly class, now it is individual
  2. Training to be a forensic biologist
    • They are civilian scientists or civilian members of the RCMP
    • Minimum of B.Sc (Hon) in biology, molecular biology, biochemistry, chemistry
    • Technician - Evidence Recovery Unit PCR Analyst (3-5 yrs.)
    • Specialist – expert testimony
    • Reporting Officer – statistics/probability
    • If no hons. or only diploma – Technician
  3. Evidence Recovery Unit
    • Search Technologists
    • Locate and isolate and recover forensically important evidence eg.
    • Blood
    • Semen
    • Entry level position
    • Presumptive tests
  4. Hair – class characteristics
    • Shed everywhere
    • Shed all the time
    • Cuticle
    • Cortex
    • Medulla
  5. Important to ID Species
    • Is it human or animal
    • Scale Patterns – in nail polish
    • If animal – related to scene?
    • Pet dog of offender?
  6. Hair Examination
    • Human – thin medulla, smooth cuticle
    • Where is hair from on body?
    • Beard – triangular in X-section 
    • Scalp, pubic – oval
    • Pubic – highly twisted
    • Ancestry?
    • Negroid – flat, oval in X-section, very curled, dense uneven pigment 
    • Mongoloid – wide in X-section, coarse pigment
    • Caucasoid - oval-round in X section, fine to coarse pigment evenly distributed
    • Treated hair – breaks easily
  7. Hair Colllection
    • Need a comparison sample – compare unknown hair at scene with suspect and victim
    • Adequate sample required – RCMP:
    • 80-100 PULLED scalp hairs 
    • 30-50 PULLED pubic hairs
    • From all over region
  8. Results of Examination
    • Positive – consistent with donor
    • Consistent with that person
    • Coincidental match

    • Negative – not consistent with donor
    • Did NOT come from that person
    • Known sample was not representative, or contained too few hairs
  9. Class evidence of hair?
    Not usually individualizing – corroborative evidence

    • Hair root – DNA
    • Hair shaft - mtDNA
  10. Body Fluids –sexual assault kit
    • Need samples from victim AND suspect
    • If alive – medical personnel
    • If deceased – pathologist
    • Semen – Swabs from vagina, cervix, rectum, anus and mouth
    • External area
    • Allowed to dry (prevents mold)
    • Pubic combing:
    • Hair from attacker?
    • Control sample from victim?
    • Fingernail scrapings (if dead, bag hands)
    • Unpleasant, victim must consent
    • If unconscious, evidence lost
    • Bill C-104
    • Suspect – all samples
  11. Blood evidence
    • If on person – swabs as before
    • On items – swab - care with other evidence
    • Clothes, weapons? Dry paper bag
    • At scene?
    • Visible? – swab or collect item
    • Not visible? LUMINOL
  12. luminol
    • Presumptive test
    • Might be blood
    • False positives
    • Dingo baby case
  13. Presumptive Tests for Blood
    • Cheap , quick:
    • Luminolo
    • Haemastix test:
    • -False positives with e.g. rust, bleach, vegetable extract
    • -Interferes with DNA extraction
    • Bluestar – ok with DNA
    • Kastle Meyer/Phenylphthalein
  14. Confirmatory tests for blood
    • Haemachromagen test
    • No false positives
    • Only shows it is blood, could be from any animal
  15. Presumptive Tests for Semen
    • Fast Blue test (Acid phosphatase colour test)
    • From prostate gland – 400X semen/other fluids
    • Sodium alphnapththylphosphate and fast blue B dye
    • rapid positive result = semen 
    • Vasectemized males – still positive
    • Run piece of moist filter paper over area
    • False positives with e.g. fungi, contraceptive creams – slower to react
  16. Confirmatory tests for semen
    • Spermatozoa
    • In past - PSA or p30 test (Prostate Specific Antigen)
    • Was believed only in semen BUT now found to be present in breast milk, amniotic fluid, female urine, but low
    • Vaginal fluids. Same levels as males
  17. Individualize the male?
    • Sperm – DNA
    • Vasectomy - no sperm
    • Can man be identified?
    • Is sperm the only DNA in sample?
    • No, epithelial cells rubbed off during intercourse – have DNA
  18. Time Factor for semen
    • Vaginal sample:
    • Motile sperm – 8 h
    • Non-motile sperm - 16 h
    • Just sperm heads - <48h
    • Oral samples Up to 6 h (rare)
    • Anal and rectal samples
    • Up to 20 h
    • All swabs will be taken
  19. DNA history and information
    • 1985 – DNA fingerprinting
    • DNA first used in case in Canada in 1989
    • Genetic code of life
    • Chromosomes
    • DNA (Deoxyribonucleic acid) – makes up chromosomes (strings of genes)
    • All cells (except red blood cells)
    • Many nucleotides = DNA
    • Sections of DNA “code” for a chemical product
    • Coding sections = genes
    • One molecule of DNA = many genes
    • DNA molecule – compact – fits into cell nucleus – called a chromosome
  20. Chromosomes
    • Humans have 23 pairs of chromosomes (46 total)  
    • All come in pairs
    • 22 regular or autosomal pairs
    • 1 pair of sex chromosomes X, Y
    • Everyone has 2 chr.1’s, 2 chr.2’s, 2 chr.3’s etc.
    • Sex always determined by male! Chromosomes – strings of genes, all in pairs
    • Both chromosomes in a pair have same genes
    • May have different versions or alleles
    • e.g. gene for eye colour is on middle of chr. 15
    • Both members of pair of chr. 15 have eye colour gene in same place.
    • Alleles could be blue, green, brown, violet
    • Each person only has 2 - so 2 blue, or 2 brown, or 1 brown and 1 green etc.
  21. Reproduction
    • Human – diploid – chromosomes in pairs
    • 46 chromosomes – viable human
    • 46+46=92 – not a viable human
    • MUST have exact number of genes and chromosomes, not one more, nor less
    • Half of each pair comes from mother, half from father
    • Meiosis – process in ovaries and testes to reduce chr. number in half 46
    • 23
  22. Egg (23) + sperm (23) = 46
    • Meiosis – doubles the chromosome material in testes and ovaries so briefly 4
    • Then SHUFFLES the genes between the 4
    • Then reduces chromosome number to 23 in each sperm or egg
    • Each sperm or egg is unique
    • Unique egg + unique sperm = 1 unique complete cell
    • Divides into 2, then 4, 8, 16 etc. = 1 baby
    • All cells in human body the same
    • 99% of human DNA identical
    • Most functions identical in everyone e.g.
    • Eyes function the same way
    • Stomach digests in same way
    • Structure of skin identical
    • Only 1% different
  23. DNA typing
    • In between the genes - junk DNA
    • Short Tandem repeats (STR’s)
    • Repetition of sequences of DNA
    • Don’t know what they do, but VERY VARIABLE between people
    • In world - numerous possibilities for number of times a particular sequence of base letters can repeat themselves on a DNA strand
    • even higher when look at 2 places on chromosome, or 3 etc.
    • Look at areas in chromosomes which are known to be very variable
  24. RFLP
    • Restriction Fragment Length Polymorphisms
    • Old technique
    • Needed good quality DNA, not degraded
    • Large amounts of blood needed
    • 6-8 weeks
    • expensive
  25. PCR
    • Polymerase Chain Reaction
    • Makes many copies of original
    • Degraded DNA OK
    • Tiny amount of blood neededo 1-2 weeks
    • Inexpensive ~25c/sample
    • Easily stored in database
  26. High Profile cases
    • Gail Miller – killed before DNA fingerprinting available
    • Christine Jessop – only RFLP available, too degraded
    • Innocent men wrongly convicted
    • Later re-examination of degraded DNA with PCR
    • Exonerated David Milgaard & Guy Paul Morin
  27. Contamination?
    • May magnify wrong piece of DNA
    • Scene security:
    • bunny suits,
    • double gloves
    • Separate teams for related scenes
    • Lab security:
    • Separate labs
    • Separate scientists
  28. Case enters lab
    • 1. Stains identified
    • 2. Cut out
    • 3. Extract and purify DNA
    • 4. PCR
    • 5. Analyze results from scene, controls from victim, known from suspect (all done separately, in different rooms by different scientists)
    • 6. Determine statistical significance – based on population databases
    • 7. Prepare report
    • 8. Independent File Review
    • Some of original stain kept for opposing counsel
    • Double-blind studies to check accuracy
  29. Databases
    • Determine statistical significance of a result
    • Look at frequency of profile in the database - at each locus
    • Frequency at 1st locus – 1 in 50,000
    • Frequency at 2nd locus – 1 in 25,000
    • Chance of having both – 1 in 1,250,000
    • Shows how rare that profile is in that population
  30. Probabilities
    • e.g. 1 in 45 billion
    • Not probability of guilt!
    • Does not mean it IS his DNA
    • Means that probability that t came from someone else is very low
    • Affected by relatedness
    • Familial DNA
  31. Databases in Canada
    • 4 – based on ethnic background
    • Each has different probabilities for each profile
    • BUT all frequencies so high, can use different databases interchangeably
  32. Warrants
    • Bill C 104 – can get warrant to get DNA sample
    • Bill C 3 – DNA databank
  33. DNA and Mt DNA
    • The “other” DNA – Mitochondrial DNA (mtDNA)
    • Nuclear DNA:
    • in nucleus, in nearly every cell
    • from both parents
    • unique
    • mtDNA:
    • many copies in each cell, in mitochondria
    • from Mother only
    • Same as mother
  34. MtDNA
    • Mitochondria – powerhouses of the cell
    • Have their own DNA, unique from cell
    • All mitochondria in a person come from first mitochondria in zygote – from mother
    • No shuffling
    • So all mtDNA in a person are IDENTICAL to their mother, brothers and sisters, grandmother, etc.
    • Same throughout maternal line
    • Can identify to that family group
    • Found in hair shaft
    • Easier to recover from very old sources
    • Not performed forensically in Canada
Author
Csouch
ID
318889
Card Set
CRIM 355
Description
Part 1 & 2
Updated