forensics serology. forensic serology analysis and screening of body fluids usually hand-in-hand...
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Forensics Serology
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Forensic Serology
Analysis and screening of body fluids
Usually hand-in-hand with DNA analysis
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Common Cases
Most involve sexual assaults (sexual assault kits, complainant clothing, bedding, suspect clothing)
Others: homicides, aggravated assault, burglaries (blood from crime scene, clothing, weapons, etc)
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Collecting Specimens • If its small enough, its simply brought to the lab• Otherwise, collected on a cotton swab or part of the evidence
with bodily fluid is cut off from the item for submission
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Bodily Fluids• Blood• Semen• Saliva• Sweat• Feces• Urine
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Excreted vs. Secreted • Excretion is the removal of material • Sweat, breast milk, earwax, feces, chyme, bile, vomit, aqueous
humour (watery substance that covers the eye), sebum (skin oil), urine
• Secretion is movement of material from one point to another • Blood/plasma, semen, saliva, serum
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Testing• Definitive – The sample is definitely the specific target and
cannot possibly be something else• Presumptive• The sample is definitely not a certain substance• The sample is probably the substance
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Saliva Tests• Reveal• Disease markers (HIV, cancer)• Viral infections• Presence of therapeutic & illicit drugs (only 12-24 hours) (THC,
heroine, cocaine, amphetamines)
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Saliva• 99.5% - water• 0.5% - electrolytes, mucus, glycoproteins, enzymes, and
antibacterial compounds• Humans produce 1.0 – 1.5 L a day!• Alpha-amylase – breaks down complex carbohydrates into
smaller sugar molecules (breaks down starch)• B-amylase: Plant & bacterial sources• A-amylase: HSA (human saliva), HPA (human pancreas)
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Alpha-Amylase Overlay– Presumptive Assay• Qualitative only (positive or negative)• Spray a Whatman paper circle with solution of soluble starch • Lay the paper down over the suspected saliva stain• Leave in contact with stain for 20 minutes
• Incubate in a 37 deg moisture chamber for 1 hour, then dry• Spray with iodine and look for a lack of color change to deep
blue-black
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Phadebas Method – Presumptive • Tablets consist of insoluble starch polymers to which a blue
dye has been covalently bound• Add putative saliva stain to water • Add tablet • When amylase is present:• Polymers are degraded• Dye is liberated and becomes soluble • Concentration of soluble dye is measured by spectrophotometry
at 620 nm
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Direct, Less Presumptive Test• Lateral Flow Immunochromatographic Strip Test or Rapid Stain
Identification (RSID) Saliva kits• Detects for the a-amylase molecule itself, specifically the one
in human saliva• Can test various surfaces such as those on paper, cigarette
butts, plastic or glass bottles, metal cans, etc.• Tricky….. Why?
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Feces / Urine• Not as common• Swabbed, bagged, placed in vials to be air-tight and prevent
cross-contamination
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Factors that Effect Urine• Amount produced – liquid intake, temperature, physical
activity• What effects different components found in urine? Health and
diet
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What’s in Urine• Urochrome pigment (what makes the yellow color)• Crystalline substances • Epithelial cells from the urinary tract lining
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Urea• Second largest constituent of urine & the product of the
breakdown of protein • Body puts of ~30g a day• Crystals form when combined with xanthydrol and acetic acid• Urea will also turn pink/red in the presence of p-
dimethylaminocinnamaldehyde (DMAC)
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Can you find DNA in urine?• Sometimes….. But it’s poor• There’s no DNA in actual urine• However, since it is stored in the bladder and goes through the
urethra, you can sometimes get the lining epithelial cells• Better with a liquid sample properly stored• Who has more DNA-containing cellular material in their urine
– male or female?
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Urine Test• Finding it – color, smell, chemical mapping• Presumptive • Smell? Ammonia (from the break down of urea)• Methods? Microcrystalline tests, color tests, TLC (thin layer
chromatography), GC/MS, radial gel diffusion, immunoassays
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Presumptive Assay• Prepare Whatman filter paper circle with one drop of
bromothymol blue, a pH indicator dye• Yellow-green at pH 6• Aqua blue at pH greater than 7.6
• Allow bromothymol blue to dry• Add drop of extract from evidence sample on top of dye, then
add drop of urease • If urea present, urease will degrade to ammonia• Ammonia will raise pH and dye will turn aqua blue
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Immunological Assay• RSID-urine• Tests Tamm Horsefall glycoprotein (abundant in urine)• Not specific for human urine
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Feces• Brown color due to bilirubin• Smell? Break down of amino acids into skatole, indole, and
methyl-mercaptan by bacteria• Made of dead bacteria (that aids in digestion), living bacteria,
protein, undigested food residue (fiber), waste material from food, cellular linings, fat, salts, mucus from intestines and the liver
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Feces Detection – Confirmation Assay
• Compound microscope (extract it in water, stain using KPIC, and mount on a slide)
• Look for animal and plant cells (digestion)
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Presumptive Assay• Prepare extract of feces stain• Oxidize urobilinogen (a breakdown compound from bilirubin)
to urobilin• Add zinc chloride• If urobilin present, extract will fluoresce under UV light• Glows green!• Used in cases of “gassing” in prisons