Final exam Flashcards
Francis Bacon – Observation
Scientists should be disinterested observers
Collect observations without prejudice or preconception
Multiple observations lead to emerging patterns that can provide “truths about nature”.
Karl Popper – Falsification
Hypothesis emerges from observation
Logical predictions follow from the hypothesis
Predictions can be tested in such a way as to allow for rejection of the hypothesis.
Hypotheses can only be “rejected” or “fail to be rejected”,
they can never be proven.
Thomas Kuhn – Paradigm shift
He suggested that there is a consensual world view that involves an agreed upon set of assumptions, methods, and language (a paradigm) in which science progresses incrementally.
At a certain point there builds up difficulties and eventually a scientific revolution brings about a new paradigm.
Science (like law) is an adversarial process:
differences
where the falsification of hypotheses and construction of alternative hypotheses occurs. No feelings in science
Differnces – timing, testing of hypothesis, language
Comparison of science & the law
Language:
error and mistake. Used interchangeably in law. Error is intrinsic to any scientific measurement and is part of the data interpretation.
Objective:
Law – justice within a time limit. A decision has to be made.
Science – truth with no time limit. A decision is not required.
Individualization:
advantage and problem
assume indistinguishable marks produced by a single object and those produced by different people or objects are observably different.
Advantage/appeal: enables forensic scientists to draw bold, definitive conclusions.
PROBLEM: excuses forensic sciences from developing: measures of object attributes, collecting population data on the frequencies of variations in those attributes, testing attribute independence, and calculating and explaining probability that different objects share common observable attributes.
Innocence project evidence
Stephen Cowan - Fingerprint
Ray Crone - Bite mark
J.R. Brouingaard - Head/Pubic hair
Ronald Cotton - Eye witness
Frye Standard (1923): “general acceptance”
the general acceptance of the scientific technique or principle
Daubert:
new rules for admissibility of scientific expert testimony. Difficult for courts to sort good from bad science, whether the bad science is a matter of perjury, incompetence, or unclear language.
Expert Testimony:
peer review, error rates, adequate testing, regular standards and techniques, general acceptance.
Theoretical underpinnings of methods must yield testable predictions by means of which the theory could be falsified.
Methods preferably published in peer-reviewed journal.
Known rate of error that can be used to evaluate results.
Methods generally accepted by relevant scientific community.
Blood tests
colour tests such as Kastle-Mayer/Hemastix
luminescence tests: luminol/Bluestar
antibody precipitin tests, specific for human blood: Hematrace test.
Semen Tests
Direct microscopic observations
acid phosphatase test (colour test)
prostate specific antigen tests (P30 human specific)
Saliva
Phadebas Test (for alpha-amylase)
how is Species identification perfromed
Species identification is performed using DNA markers (mitochondrial DNA sequencing).
Sex determination
PCR amplification of X and Y chromosomespecific DNA allows sex determination. .
Individual identification
DNA analysis can identify evidence taken from an illegal kill site and “link” it to a sample from suspected poacher
Population identification
Databases needed for population identification (e.g. reference samples).
Parentage
Establish if animals in a captive breeding program are the offspring of registered breeding pairs or illegally obtained from wild stocks (again with STRs or microsatellite markers)
Tests you can’t mix together
DNA analysis + chemical testing
Serological testing + DNA analysis
Trace evidence + DNA analysis
Toxicology + DNA analysis
Parentage Biology
DNA Extraction –> DNA Quantitation –> PCR Amplification of Multiple STR markers
Parentage technology
Separation and Detection of PCR Products (STR Alleles) –> Sample Genotype Determination
Parentage genetics
Comparison of Sample Genotype to Other Sample Results –> If match occurs, comparison of DNA profile to population databases –> Generation of Case Report with Probability of Random Match
PCR
copies
used molecular biology technique that allows scientists to make millions or even billions of copies of a specific segment of DNA.
genotype
A genotype refers to the genetic makeup of an organism, which is the collection of genes inherited from its parent
random probability match
the significance of a DNA match and its potential occurrence in the broader population
Ex. Not many people have red hair so if red is found you can look at the general population and realize that there arent many gingers so it has to be the suspect
human vs wildlife forensics
Same principles as human forensics.
Main difference: need to identify and distinguish between a variety of species. not for humans
Differential extraction
The purpose of differential extraction is to isolate DNA from different cell types (for example, sperm cells and epithelial cells from the victim) based on their different physical and chemical properties
What would a profile look like for STR for males
3 peaks then there is less than 2 people involved
Each marker represents a specific region on the Y chromosome where the number of repeated DNA sequences (repeats) varies among individuals.
parentage in humans on chart
baby inherits #’s from mom or dad
National DNA Data Bank: two principal programs
Convicted Offender Index (COI) : electronic index developed from DNA profiles collected from offenders convicted of designated primary and secondary offences.
The Crime Scene Index (CSI) : separate electronic index composed of DNA profiles obtained from crime scene investigations.
Missing person index
2 ways to identify species of organism
DNA analysis and Mass spectrometry
Manner of death
Homicide, suicide, accidental, natural, unknown!!!
Classification of trauma
Mechanical - Sharp force , Blunt force, Gun shot,
Chemical (e.g., acid)
Thermal - Hypo or hyperthermia
Electrical
Radiation
Blast
Algor mortis
temp + time of death
Rigor mortis
estimate the time since death. It typically starts within a few hours after death, peaks around 12-24 hours, and then gradually dissipates over the following 24-48 hours
Livor mortis
moving of a body, time fo death, cause of death
Lividity begins to appear within 1-2 hours after death, becomes fixed at around 8-12 hours
life cycles of flies
1st,2nd,3rd instars
active transport
Active transport is a biological process that moves molecules or ions across a cell membrane against their concentration gradient.
How to tell age, sex, ancestry and disease in bones
Pelvis, femur, skull – sex
Bone fusion, teeth development - age
Proportions, bone length – ancestry
Bone abnormities - disease
What bones/teeth present after exposure to harsh conditions (water, temp, UV, time)
Water - Bones become waterlogged and porous
Temp - Too hot can lead to burns making the bones brittle. Too cold can lead to freeze-thaw cycles
Time - Fossilization
Teeth for ID when?
Mass disasters, fire related, unidentified human remains, missing person and age estimation
bite mark analysis issues
active process from interactions of mandible, maxilla, victim response
other factors affect appearance such as the medium, pressure, directionality and time
human skin has elastic properties
roles of a forensic entomologist in a death investigation?
study the growth of bugs on a body to help forensic inveatiagtions are consulted in how the taphonomic process might influence time since death estimations.
ADD use
Used for Determining the age of the oldest fly (ADD) found on or near the body provides an initial estimation of the time since death, as it indicates when the first blowflies arrived to lay eggs.
ADH use
The eggs laid by blowflies hatch into larvae within a specific timeframe, depending on environmental conditions such as temperature.
minimum growth temp
Forensic entomologists use accumulated temperature data (degree-days) to estimate the time since egg deposition and larval development
ADD + ADH math
24 hours x (mean temp – lower developmental threshold)
Explain role of a forensic toxicologist
forensic toxicologist primarily concerned with identifying and measuring drugs and toxins/poisons in body fluids and human tissues in legal context
how alcohol is absorbed, transported, eliminated
Alcohol is removed from the bloodstream by a combination of metabolism, excretion, and evaporation.
Drug vs Poison
Drug - Any chemical substance, other than one that is required for normal body function
Poison - A poison is any substance when applied or introduced into the body causes damage, disturbance of bodily function, adverse effects or death
Truscott case and timing of egg deposition
Size of maggots made it so that he couldn’t have been there when the victim die
spontaneous generation
16 Century Francesco Redi discovered link between flies and maggots; rejected hypothesis that some life from spontaneous generation of inanimate matter
Describe chemical reactions that start and sustain a fire
Starting fire - Ignition temp –> combustion reaction
Sustaining fire - Chain reaction, oxygen supply and fuel availability
types of fires
Accidential, arson and spontaneous combustion
Describe various signs that indicate the point of origin of a fire
Locating origin – creating V patterns, streamers
Describe various signs indicative of accelerants starting a fire
Accelerants – sniffers, photoionization detectors
Describe ways to locate collect, preserve, and identify fire evidence that is volatile
Headspace method, Vapour concentration method, Gas chromatography
Headspace method
heating an airtight container
vapour concentration method
placing a charcoal strip in the airtight debris container when it is heated. The charcoal strip absorbs much of the vapors during heating.
gas chromatography
separates the hydrocarbon components and produces a chromatographic pattern characteristic of a particular petroleum product
Primary explosives
ultra-sensitive to heat, shock, or friction and provide the major ingredients found in blasting caps or primers used to detonate other explosives.
Secondary explosives
relatively insensitive to heat, shock, or friction and will normally burn rather than detonate if ignited in small quantities in the open air.
how computers receive, store, and transmit data
Hard disk drives, NAS and RAID
types of computer crimes
Crimes where computers are the target – like network intrusion, alteration of data
Crimes where the computer is an instrument of crime - like theft, fraud, cyberstalking
Crimes where the computer is incidental to the crime – essentially, the computer facilitates the crime – like money laundering, child pornography, and organized crime
Crimes associated with the prevalence of computers – like piracy, and identity theft
who commits computer crimes?
Hackers/Crackers - These are people who can overcome/disable computer security.
White Hats - These are individuals that are considered “ethical” hackers or those who are tasked with testing computer security systems for vulnerabilities.
Black Hats - These are individuals would break into computer systems/networks with ill-intent.
Gray Hats - These individuals sometimes break laws to evade computer security, but they do not have the same ill-intent as black hats
Describe the basics of how both latent and visible data are analyzed
Visible Data – these include data that are easily viewed and accessed on the computer, such as .doc files created by software programs. This can also include temporary files that can be recovered if power is turned off suddenly (e.g., you pulled the plug on the computer).
Latent Data – these are data not directly visible to the user.
Describe how IP addresses can/can’t assist computer forensic investigations data is conserved relative to computer data
IP masking - encrypted VPN service or proxy server
VPN - A virtual private network (VPN) is a way to send and receive data across shared or public networks as if their computing devices were directly connected within a private network
Malware
Virus, Worm, Trojan Horse, Spyware, Adware
Differences b/w clinical and forensic - Scope
Psychology - Assessments focus on the diagnosis and/or treatment of their patient
Forensic - Evaluations focus more on narrowly defined, nonclinical events or interactions, with diagnosis and/or treatment in the background
Relationship and dynamics - clinical vs forensic
Clinical – emphasizes care and trust with empathy
Forensic - Forensic psychologists may not ethically nurture the client’s perception that they are there in a ‘helping’ role. They must maintain an emotional distance
Importance of clients perspective - clinical vs forensic
Clinical – focus is on understanding the clients unique view of the situation or problem
Forensic – focus is more objective and the client’s view is secondary
projective tests
if an individual is shown an abstract picture, their responses will convey aspects of their personality.
Rorschach test
10 inkblots
Thematic Apperception Test (TAT)
shown pictures and asked to create a story from pictures.
Projective Figure Drawings
subject draws a pictures that provide information about inner thoughts/fantasies
what is a Intellectual and Cognitive Assessment
evaluations about offender’s criminal responsibility or competency can change dramatically if found intellectually limited or mentally challenged.
