forensics serology. forensic serology analysis and screening of body fluids usually hand-in-hand...

Forensics Serology

Forensic Serology

Analysis and screening of body fluids

Usually hand-in-hand with DNA analysis

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)

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

Bodily Fluids• Blood• Semen• Saliva• Sweat• Feces• Urine

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

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

Saliva Tests• Reveal• Disease markers (HIV, cancer)• Viral infections• Presence of therapeutic & illicit drugs (only 12-24 hours) (THC,

heroine, cocaine, amphetamines)

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)

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

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

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?

Feces / Urine• Not as common• Swabbed, bagged, placed in vials to be air-tight and prevent

cross-contamination

Factors that Effect Urine• Amount produced – liquid intake, temperature, physical

activity• What effects different components found in urine? Health and

diet

What’s in Urine• Urochrome pigment (what makes the yellow color)• Crystalline substances • Epithelial cells from the urinary tract lining

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)

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?

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

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

Immunological Assay• RSID-urine• Tests Tamm Horsefall glycoprotein (abundant in urine)• Not specific for human urine

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

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)

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