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- hair
- body fluids: blood, semen, urine, saliva
- DNA
hair: 1. cuticle (covering) 2. cortex (color) 3. medulla (canal)
sexual assault kit:
- used to collect evidence
- contains swabs, pubic comb
presumptive test - cheap, quick test, covers larger areas, have false positives
confirmatory test - more expensive, no false positives
blood:
- presumptive test - haemastix test, luminol
- confirmatory test - Haemochromagen chemical test, DNA typing
semen:
- presumptive test - fast blue test (phosphate color test)
- confirmatory test - microscope, prostate specific antigen (PSA)- relies on semen, not sperm, DNA typing
- must be collected within 48 hrs, if later, sperm is destroyed
DNA:
- every indiv. has dif’t lengths of tandem repeats
- when 2 samples compared, several loci known to have STR’s (Short Tandem Repeats) will be examined to increase validity of results
- restriction fragment length polymorphisms (rflp) - expensive, slow 6-8 weeks, need high quality DNA
- polymerase chain reaction (pcr) - inexpensive, fast 1-2 weeks, may also amplify contaminants
- database on frequencies of STR used to see if results are statistically significant
- Bill C-104 allows DNA sample to be collected under warrant
- buccal swab - non-invasive method of collecting DNA by rubbing swab inside cheek of the mouth
- mtDNA - mitochondrial DNA - inherited from mother alone, more useful in identifying victim than suspect
- egg - provides genetic material, cytoplasm & all other cell materials
forensic chemistry:
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- paint, glass chips, fibres, bomb, arson, drywall, glues, cleaners & tape
- qualitative and quantitative (% composition)
- mass spectromphotometry: characterize & identify many purified substances
- gas chromatography: (purifies) separates components of a mixture of substances & tentatively identifies them
Significance of evidence:
- explain in jury in terms of significance
- probability that evidence will be found on someone else
- depends on circumstances
fibre - color, refractive index, infrared spectrophotometry results
paint - many layers, # of variants determine year, make, model
fire - any accelerants?
bomb - how was it constructed, composition, detonating mechanism, Explosive ² timers, detonators, fuses, batteries, something to hold it together ² duct tape commonly used
explosion - fast immense pressure (expand & compress layers of surrounding air
) ² stretches & explodes rigid pipe producing sharpnel (sharp, deadly fragments)
types of explosive (according to their rate of decomposition):
i. low explosive - decomposes slowly "deflagration", used for propelling rockets in a specific direction
ii. high explosive - usually nitration based, decomposes quickly "detonation" due to shock
a. primary explosive - ultrasensitive to heat shock, detonates easily and violently
b. secondary explosive - insensitive to shock, usually detonated during initial explosion ie dynamite, TNT
forensic toxicology
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1. deals with detection of drugs or poisons
2. involves interpreting findings - physiological/behavioral effects
determine WHAT DRUG it is and HOW MUCH of it is present & WHAT BEHAVIOUR a person would make
- drug metabolites deposited in hair
- assist in establishing true cause of death
- “the dose makes the poison” - anything can be a poison, depending on dose, ie. oxygen & water = too much or too little can cause death
2 main parts of forensic toxicology investigation:
1. analytical phase - specimen (eg. blood, urine) is analyzed for drug's metabolites, smaller chemical substances to identify the drug, gas chrom. & mass spectro
2. interpretive phase - when drug was last taken, amount, what symptoms, chronic (drug taken over long period) or acute (sudden, one-time exposure)
specimens:
blood - easy to get, primarily used for drug screening (confirming and quantification), but it needs to be purified 'dirty' speciment, invasive, may not be available after body has decomposed, decomposition of proteins by bacteria (putrefaction) produces alcohol in blood (must take blood samples from diff. parts of the body)
urine - second most popular for substance analysis (confirmation only), clean specimen, less invasive than blood
hair - determine drug history, not invasive, only from criminal cases in Canada
virtuous humor (eye) - protected from putrefaction
other other non-biological exhibits like surrounding syringe, spoons, pipes, medication, food
presumptive tests - narrow down to a class of drugs
confirmatory tests - gas chrom. & mass spectro
clandestine lab - produces illegal drugs, dangerous so forensic chemists help police identify danger and identify what they want to collect for evidence
forensic toolmark
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- determine whether tool mark was produced by particular item
- physical matching: usually firearms or tool marks, but also physically matching glass from a hit & run or broken scissors or knife tips in a wound
- tool: any hard object that makes an impression in a softer object (ie. Chisels, hammers, tire impressions in snow, footprint in blood)
- restore serial #
- attend autopsies to reconstruct event, entry or exit wound, how far was the shot was fired
2 types of tool marks:
1. impressed - no movement of tool other than force or blow
2. striated - pressed with sliding motion
class characteristics - eg width and shape of knife blade, used for elimination of tools
individual/accidental characteristics - formed during manufacturing or use,
examiner makes impression of suspect tool (in very soft substance), which can then be compared w/ suspect mark directly
some cases, similarities btw. tool marks from dif’t tools
- dif’cs btw. tool marks made by same tool
causes of false similarities: same manufacture carryovers (dirt, imperfections) between tools, by chance, unfamiliar tool
causes of false differences: same tool corrodes over time, over use, diff't softness of objects, tool deliberately changed, cleaning
serial # restoration:
- strained areas will dissolve faster (using etching agent eg acid) than unstrained metal & # will reappear, doesn't work for laser writing because they don't strain metal
Forensic Firearms
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- cartridge loaded in gun has many parts ( metal case contains propellants, gunpowder, bullet) (*gunpowder needs small charge to set it off - tiny granules)
base of cartridge usually contains primer ² ignites smokeless powder & ejects bullet when struck (see http://en.wikipedia.org/wiki/Bullet)
A modern cartridge consists of the following:
1. the bullet itself, which serves as the projectile;
2. the case, which holds all parts together;
3. the propellant, for example gunpowder or cordite;
4. the rim, part of the casing used for loading;
5. the primer, which ignites the propellant.
- bullet (projectile or “slug”): piece of cartridge shot out of gun
bullet types:
1. full metal jacket - used in military, disables target, prevents from fragmenting
2. hollow point - mushrooms, used in hunting,
- A hollow point is an expanding bullet that has a pit or hollowed out shape in its tip, generally intended to cause the bullet to expand upon entering a target in order to decrease penetration and disrupt more tissue as it travels through the target
http://en.wikipedia.org/wiki/Full_Metal_Jacket_bullet
Whereas hollow point and soft-tipped bullets are designed to expand upon impact, fully metal jacketed bullets are technically limited in mechanisms to increase round expansion. In some cases this leads to smaller target damage, although not in all instances.
cocking - when cocked, ready to be fired
² moves hammer towards webbing btw. thumb & forefinger
² trigger releases hammer & it falls rapidly, striking primer
² bullet (softer object) travels @ great speed along hard barrel (tool)
barrel drilled again to produce rifling: series of spiral grooves (if straight barrel, tumble over end & not fly in straight line)
dif’c in # of grooves cut, width btw. them, whether spin bullet clockwise or anticlockwise
diameter of original barrel, before rifling, determines caliber of gun (class characteristic)
* most test bullets in large water tank ² water slows bullet rapidly
test bullet & suspect bullet compared directly w/ suspect bullet using bullet holder underneath one objective of a comparison microscope
- hammer = tool (hard object) ² leaves mark on softer object, primer
like in tools, similarities btw. bullets fired by dif’t guns or difc’s in bullets fired by same gun
diff. when using diff types of bullets not designed for the gun, cleaning, cheap guns
gunshot residue (powder never totally burns):
- gun fired ² leaves gunpowder residue behind
- some gun powerder flashes back @ shooter
gunshot residue analysis - determine how far (distance) shooter was from target who fired shot
distance of gun from target determined by: - amt - type - pattern of residue
Types of shots:
1. contact shots - nearly all unburned powder is forced directly into wound, skin around bullet wound tears in star shape pattern
http://www.ojp.usdoj.gov/nij/training/firearms-training/module12/fir_m12_t06_02.htm
2. Close distance shot (less than 1 inch): bullet wound has rim of heavy concentration of smoke-like vaporous lead, clothing is scorched,
3. Shot from 12 - 18 inches: soot (incomplete combustion of carbon) & powder deposited around bullet hole together
4. Shot from 24 inches: only soot deposited on target
5. Shot from 25-36 inches: scattered specks of unburned/partially burned gunpowder grains
6. Shot from 3+ feet: usually no residue on target
Primer Residue on Hands - some primer residue goes back to shooter
- doesn't stay in hands very long
- dermal nitrate test - hot wax to pick up traces of nitrate, false positives (nitrate in urine and tobacco)
- primer residue test - no false positives, primer residue sticks to webbing of skin, closeby people may have it too, but the shooter has MORE, so AMOUNT matters
gunshot wounds:
1. temporal cavity - lasts millisecond - causes tremendous damage, tear tissue, destroy organs, can be as large as a cannonball, massive stretching caused by gases expanding as bullet passes thru body.
2. permanent cavity - crushing of tissue & bone caused by bullet itself & if only as large as bullet itself, will heal unless fatal
1. hollow point bullet: mushrooms on contact ² very large wound - fragments
Ie. civilian ammo
2. full metal jacket: no mushrooming or fragmentation
Ie. miliary ammo ² aim to disable, not kill
Questioned Documents (QD)
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- Any object which contains signs, symbols or marks either visible, partially visible or invisible, which convey a meaning to someone
- Handwriting is unique if: reasonable amount of writing and executed freely and fluently
Graphology is NOT QD, Graphology is determining personality from handwriting, like fortune telling
Children - copies letter from books, parents, relatives
Adult – writing is a semi-conscious habit
Habits very hard to change or disguise
Class Characteristics
- from same copybook
- from same grade 1 teacher
- restricted to certain profession
- bubble font in north american teenage girls
- visually impaired?
individual characteristics
- due to diff perception
- diff in physical dexterity
- bad habbits
- from influencial people
Natural Variation
- Usual and normal deviations that occur within repeated specimens of a person’s handwriting e.g. signature – no two ever the same
Types of comparison samples:
1. collected samples - collected from everyday life
pros: undisguised, natural variation, contemporary?
cons: contain diff. text from questioned document, the real author?
2. requested samples - under warrant, watched by police
pros: knows real author, questioned document can be duplicated
cons: maybe disguised, nervous, not contemporary (at the same time as QD)
Obtaining Requested Samples
Dictate – rapidly, adjusting speed
Do not include punctuation
Must not see original
Seated comfortably (or as for QD)
Duplicate writing instrument and material
Repeat text, paragraph X3, signature X15
Remove specimen after written
Text must include all words, numbers of QD
Duplicate size of QD
Duplicate style of QD – e.g. letter
If printed, ensure upper and lower case both used
prove authorship: by witness, by someone familiar with suspect's writing
Opinions
Positive identification – sample and QD written by same person, strong probability, weak probability
Can neither identify nor eliminate
Negative – prove that someone else wrote document, writing quality is better than that which suspect is capable
Factors which affect handwriting comparisons
- pen, paper
- writing position
- condition of person writing, drunk?
characteristics - pen pressure, style, slanting
Disguise - how long can you keep a lie for?
Simple, not fluent, change is rarely consistent
Altered letter design, internal consistency disrupted
Never original – several basic types
Lapses back into own style, certain features never disguised
Class characteristics – make and model of machine, e.g. font size, design, pitch, shape
Innate characteristics – characteristic which is common to a group, but not all in group, e.g. dirt in a mould for manufacture of 10 printers
Individual characteristics – actual machine, e.g. damage to a key
Photocopiers
Document – make and model of machine
Actual machine identified by trash marks, picker marks, damage
New models – leave identifying mark
Number of copies since QD
Currency? Will shut down
Typewriters
Old ribbons – could read writing directly
Newer ribbons – moves up and down, can still be read
Alteration of Documents After Their Production
Torn paper/foil/plastic
Water soaked documents, charred documents
Altered or erased
Latent impressions
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