Week 2 - Introduction To Forensic Science Flashcards
Expert witness
An individual whom the court determines to possess knowledge relevant to the trial that is no required of the average layperson
Locard’s exchange principle
Whenever two objects come into contact with each other, there is an exchange of materials between them
Scientific method
A process that uses strict guidelines to ensure careful and systematic collection, organization, and analysis of information
Questions, hypotheses that can be and are empirically tested, analyze data, re-evaluate hypotheses
Allows science to be objective
CSI effect
Dramatization of forensic science on TV has led to the belief that forensic evidence will be found at every crime scene and that a prosecutors case will always be supported by forensic evidence
In reality, most cases don’t have forensic evidence
Definition of forensic science
The application of science to the criminal and civil laws that are enforced by police agencies in a criminal justice system
Literary roots of forensic science
Sir Arthur Conan Doyle and his Sherlock Holmes
Applies serology, fingerprinting, firearms identification, document examination before it was adapted into real life investigations
Pure science
Long history, scientific method, no specific aim, curiosity driven
Valid before forensic science became a thing
Police driven science
Developed out of a specific police need, answer a police question, short history, might not have been tested, pattern evidence (fingerprints, bite marks, blood pattern analysis)
Crime scene investigator
Sworn police officers, only work crime scenes, collect evidence to take to the forensic lab
Do not interrogate anybody, handle guns, or analyze evidence
Forensic lab scientist
Civilians, analyze specimens, testify based on science, impartial, do not go to crime scene, scientific background, lab training
Evidence
Collected by ident officers, taken to lab and given to forensic scientists, scientists analyze evidence, report to police, scientist present in court
Evidence management unit
Catalogues evidence, every piece tagged with computer code so it can be monitored, destroyed evidence is logged, first step after crime scene
Evidence recovery unit
First analysis step, each exhibit is examined, evidence is sent to appropriate lab section for analysis, search, isolate, collect evidence
Some evidence may go to multiple sections
Forensic biology unit
Bodily fluids - semen, blood, tissue, hair
Identifies what it is, if its human, and who it came from
Called serology in USA
Trace evidence (forensic chemistry) unit
Non-biological substances - paint, fibre, glue, drywall, gasoline
Crimes such as hit and run, break and enter, arson, terrorism have a lot of trace evidence
Forensic toxicology unit
Toxins in bodily fluids, needles, pills, drugs
Things that can cause psychological effects
Firearms and tool marks unit
Patterns evidence
Did this gun fire this bullet? Did this tool make this mark?
Only lab section that still employs police officers
Forensic document examination unit
Questioned documents, handwriting/printing (forgery), machines that make documents, altered documents
Scientists vs technicians
Scientists - oversee the work, perform interpretations, write reports, testify
Technicians - conduct the tests
Three levels of forensic labs
Federal - FBI drug enforcement administrations laboratories, bureau of alcohol, tobacco, firearms, and explosives, US postal inspection service, defensive forensic science centre
State - networks
Local - county
Quality and services vary, basic and optional
In Canada - no specific section for photography and crime scene investigation and latent print analysis (done by Ident officers)
Forensic science history
Only widely noticed more recently, there has been many famous scientists
1st forensic lab - 1910, Edmond Locard, Lyon France in 2 attic rooms
1st forensic lab in North America - 1914, laboratories de sciences judiciaries de medicine in Montreal
1923 - first US lab, 1931 - FBI lab
Canadian lab systems
RCMP
Centre of Forensic Science
Laboratoire de Sciences
RCMP
Three labs in Vancouver, Edmonton, and Ottawa
Vancouver - biology/dna, toxicology, firearms
Edmonton - biology/dna, toxicology, trace evidence
Ottawa - biology/dna, toxicology, firearms, trace evidence
Only deals with criminal cases for police
Centre of forensic science
Toronto and Sault St. Marie
Full service - biology, trace, documents, photo, firearms, tool marks, toxicology
Attends to investigative agencies, defence, some civil
Laboratoire de Sciences
Montreal, 1914, fbi is based on it
Full service - nDNA, mtDNA, toxicology, trace, documents, firearms, toolmarks, computer forensics
Attends to any organization in Quebec - police, corrections, coroners office, wildlife, commission of health, safety, liquor department etc…
Forensic scientists in the lab
Pure scientists
A chemist may analyze gasoline, a forensic chemist may analyze gasoline from a hit and run
Analytical tests similar, but the purpose is different**
Evidence in lab may go to…
One or many sections
Example: a bloody gun would go to biology then firearms
The anthrax letters went through 10 examinations
The job of a forensic scientist
Submits reports to investigating officer
They are not there to prove the police case, they determine the truth and use forensic science as a tool
The job of a forensic scientist
Submits reports to investigating officer
They are not there to prove the police case, they determine the truth and use forensic science as a tool
Other forensic professionals
Ident officers - analyze fingerprints, pattern evidence like blood splatter
Forensic pathologists - autopsies
Consultants - anthropologists, botanists, dentists, entomologists, diatom specialists, odontologists
Facts about eye witnesses
Common way to identify a criminal
Juries trust, but 71% of wrongful US convictions are based on eyewitness testimony
Ronald Cotton case
Lay witness vs expert
Lay
Saw or heard something and will relay it to court
Can not give an opinion - like car was being driven too fast
Expert
Did not see or hear crime
Has analyzed evidence from crime
Interprets and gives opinion
Expert witness opinion evidence
More than the average person’s knowledge
Specialized that goes beyond the knowledge of the trier of fact (R. V. Mohan)
Need education/training/research/experience
Knowledge relevant to case that will assist the trier of fact in understanding - this knowledge is not expected of an everyday person
When is expert witness evidence used?
When the facts are not enough and the evidence is beyond understanding of the average person
Presented by prosecution or defence
Impartial - they are there to explain
Expert witness in court
Not an expert until qualified by judge - expert is a legal term
Counsel presents qualifications of person they want to be an expert - opposing counsel may argue
Judge will deliberate
They are an expert until dismissed - must be re-qualified for each case
Qualifications to be an expert
No set rules - education, training, experience varies
Up to judge - judge is not trained in any fields of science
Need to use vigilance - is the person actually qualified (Exxon Valdes case)
Board certification
Set levels of education and experience
American academy of forensic sciences
Punitive measures
Expert witnesses have great responsibility
Unbiased testimony - only facts and truth and only on subjects they know
Frye vs United States 1923
Frye standard
“The science must be generally accepted and well established”
Novel sciences excluded because not yet peer reviewed or published - problem because forensic science moves fast
Federal rules of evidence - rule 702
Reliability of expert witness
- qualification of witness
- testimony factually based
- based on reliable methods and principles which were reliably applied
Daubert standard
Judge became gatekeeper of if evidence is scientific, reliable, relevant, used scientific method
Guidelines
1. Has the theory been or can be tested?
2. Peer review and publication?
3. Whether known or potential error rates are acceptable?
4. Existence and maintenance of standards
5. Widespread acceptance in relevant scientific community
Daubert trilogy
Daubert 1993
Joiner 1997 - exclude if gaps between evidence and conclusion
Kumho 1999 - judge still gatekeeper, scientific and technical knowledge
Rules of evidence - Canada
Dulong vs Merrill lynch Canada 2006
- judge as gatekeeper
Mohan 1994
1. Relevant to the case
2. Necessary to assist trier of fact
3. Did not trigger any exclusionary rules
4. Presented by a properly qualified expert
NAS report
National Academy of Science 2009
Scathing on pattern evidence - fingerprints (no error rates given), bootprints, bullet matching, bite marks, blood splatter
No scientific background to prove uniqueness - but are considered as such
NAS recommendations that could impact Canada
All forensic labs should be independent of police
All practitioners should be certified
All coroners systems should be replaced with medical examiner systems
PCAST 2016
Presidents council of advisors on science and technology - created “forensic science in criminal courts”
- Clarity on scientific methods
- Determine whether feature comparison methods were valid and reliable
Trace evidence
Hair, fibre, body fluids, fingerprints, gasoline, paint, gunshot residue, bullets, writing
People leave trace evidence behind and take it away - Locard’s exchange
Physical evidence
Identification - what is it? Use reliable and replicable tests
Comparison - with reference material - do two samples have a common origin?
Characteristics of evidence
Impacts significance
Class
- associated with a group but not a single source
- can say a fibre came from a white t shirt, but cannot say which t shirt
- significance ranges from low to high
Individual
- “blood at scene comes from suspect A”
- high significance
Low significance class evidence
Fibre at scene
Millions of people may have a shirt with the same fibre
High significance class evidence
Rare fibre at scene
Less people would have the item, but still not unique
Significance depends on probability of evidence coming from somewhere else
Class evidence - car paint
Cars have several layers of paint
Databases exist to determine colour, brand, year range
Paint chips can indicate information
Ownership records
Probabilities
Must determine parent population - how many others?
Much evidence is mass produced
Class evidence can be cumulative - product rule states multiplying probabilities of each evidences lowers probability
Can almost be individualizing
Individual characteristics
Individual = accidental
Identified to one source with high degree of accuracy
High significance - DNA, fingerprints
Both individual and class characteristics
Car paint
Class - can identify group (yellow Honda civic)
Individual - actual chip may match to chipped portion on car
Bullet
Class - identify type of gun
Individual - minute striations on cartridge
Value of evidence with class characteristics
Very, but cannot point to exact source
Useful when there are no eye witnesses or individual evidence
Cautions with class evidence
Vital that examiner says its not individualizing
Jury translates “match” to mean “the one” but it could also match millions of others
