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Crim 355 Notes (Intro to Forensic Science)
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- Simon Fraser University (SFU )
- Book
- Criminalistics
Notes from the module, which comes from the textbook
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In its simplest definition, forensic science is the application of science to law.A more limited definition, given in your textbook, Criminalistics, is: “Forensic
Science is the application of science to those criminal and civil laws that are
enforced by police agencies in a criminal justice system” (p. 4). It is
important to understand that the pertinent word here is science. Originally,
the word forensic goes back to the days of the Romans and referred to a
forum for debate or argument. Today forensic simply means as applied to
law, so it is the science that matters, not the use of the word forensic. If the
issue relates to forensic chemistry, for instance, the evidence will be
analyzed by a specialist in chemistry. The data may be used for a criminal
investigation, but similar chemical analyses might equally well be conducted
in industry for commercial purposes.
Therefore, a person could not be qualified just as a “forensic scientist,” as
they could not possibly master all the sciences that are available. In other
words, you cannot be an expert in biology, chemistry, firearms analysis,
odontology, pathology, entomology, etc. A forensic scientist specializes in
one specific area and may have from 4 to 12 years of post-secondary
education in addition to continuous and on-going training. Recent TV shows
have given the public a very unrealistic idea of what true forensic science is
all about. This has led to what is now referred to as the “CSI effect,” where
the court system has false expectations of what can and cannot be expected
from the crime lab. This has led juries and judges to assume that all cases
will involve forensic evidence and will not convict if DNA is not present, even
though many if not most cases do not involve DNA. Jury members and judges
are frequently viewers so believe that what they see on television is true
science. So, they assume that a case has not been proven or even properly
investigated unless DNA is recovered and analyzed or, at the very least,
fingerprints are recovered.
Case Study. In a case in the US, a woman was raped and lived to
identify her attacker. DNA from semen was recovered from her
vagina and was individualized to the man she identified with a very
high probability. As you will see in later chapters, unlike a
fingerprint which is identified to a single person, when DNA
evidence is presented, it is never stated to specifically come from
one individual, but rather the results are phrased to state that the
chance of it coming from any OTHER individual are too staggeringly
high to be possible (e.g. the chance it comes from anyone else in
the world is 200 billion to one). In other words, it is impossible that
it could have come from anyone else. The result is the same, but the
way it is presented is different. We will discuss why when we get to
DNA, but in this case, it was clear that it was not possible the DNA
and hence the semen, could have come from any other man.
,However, the jury did not convict him, as a partially eaten
hamburger in the kitchen, which was believed to have been bitten
by the attacker, was not tested for DNA. Why would it have been
when the pertinent evidence was the semen?
DNA tests are expensive and take time. We have all heard of the backlogs at
the labs. Imagine what it would be like if every irrelevant thing was also
tested. This is having a very serious effect in court proceedings as juries and
judges expect to see forensic evidence in every case. Many of my colleagues
spend more time testifying as to why they did NOT do a certain test than
actually testifying to the evidence. In the first chapter of your textbook,
Saferstein indicates that he believes the reason Casey Anthony was not
convicted of the murder of her two-year-old daughter Caylee was due to the
CSI effect. What do you think?
Almost any science can be applied to a legal situation, so this course focuses
on those most commonly used in criminal investigations. Most of these
scientific analyses are performed in a forensic laboratory.
top ↑
Forensic Scientists versus Crime Scene
Investigators
It is important to distinguish between the scientists in the lab and the crime
scene investigators. The two are NOT the same, despite what television
shows often suggest. Television again misinforms the public about the roles
of such people as the person who collects evidence at the crime scene is also
the same person who analyzes it, chases down the bad guy (with gun in
hand), interrogates witnesses, and testifies in court—all in less than one
hour, including commercial breaks. In reality, each of these roles is
performed by different people with different careers and very different
training. On TV, in the first CSI series, lead character Grissom is supposed to
be a forensic entomologist, such as myself. However, Grissom also appears
to be a specialist in many other sciences, and goes to crime scenes,
investigates the crime, and arrests the bad guys. To be a board-certified
forensic entomologist alone, one needs at least a BSc (hons), master’s, and
PhD (about 10–12 years of post-secondary education) followed by five years
before board certification. To be a specialist in the other fields would require
the same. I once calculated that, in order to have the appropriate
qualifications, Grissom must be at least 140 years old before he took his first
case. With these requirements in mind, in this course we will discuss each of
the sciences and the types of training and jobs that each person holds.
,Crime lab scientists are bench scientists; that is, they spend their day in a
laboratory, analyzing specimens. They do not attend crime scenes (with
some very rare exceptions). They are civilians with strong core scientific
backgrounds who perform scientific analyses on evidence. They frequently
attend court to testify as expert witnesses. They are impartial scientists.
They have an absolute minimum of a three-year technical diploma in biology,
biochemistry, medical laboratory science or forensic science but a four-year
science degree is realistically needed to rise up at all in the labs. This is
followed by years of training in the lab. Some have several degrees in their
area of specialty. They receive continual training as sciences change and
evolve.
Crime scene investigators, on the other hand, are specially trained police
officers called identification specialists or Ident in Canada. It is these
identification specialists who actually go to the crime scene and collect the
evidence. Crime scene analysis is discussed in Unit 5. The Ident specialists
collect the evidence but do not analyze it. Instead, they transfer it to the
forensic lab, where it is officially handed over to the civilian crime lab
scientists, who perform the actual analyses. The evidence will be delivered to
the appropriate section after it has been collected from the scene. The
scientists analyze the evidence, submit a report back to the police and
testify to that evidence in court.
top ↑
Forensic Laboratories
Most forensic labs in Canada include the following sections or units:
Evidence Management, sometimes called the Case Receipt Unit.
When evidence has been collected at a crime scene, it is then taken
to the forensic laboratory and enters Evidence Management. Every
single exhibit is tagged with a computer code which then allows its
movements through the various units of the laboratory to be
monitored at all times. This means that when an investigator or
lawyer contacts the lab to see what progress is being made, the
Evidence Management personnel can immediately find out exactly
who has the evidence at that moment and how far the analysis has
progressed. Many analyses require a small portion of the exhibit to
be destroyed and this will also be recorded. Often an exhibit must
be examined by several sections, so this again allows the exhibit to
be tracked through the laboratory system.
Evidence Recovery. Once tagged by Evidence Management, the
exhibit will go to Evidence Recovery, where scientists will then
examine the exhibit looking for forensically significant trace
, evidence. Evidence Recovery technologists will search, locate, and
collect all forensically important material and submit it to the
appropriate unit. For example, if a bed sheet is seized from the
scene, Evidence Recovery technologists may cut out areas of the
sheet in which they can detect body fluids, such as semen, blood, or
saliva. These will be submitted to forensic biology.
Forensic Biology. Forensic biologists deal with all body fluids, such
as blood and semen as well as tissue and hair that might relate to a
crime scene. The purpose of their analyses is to identify the person
the substances came from. In the past, this section was referred to
as the serology section, but with the advent of DNA analysis, it has
become the biology section in Canada. Some of the things
described in the text ‘Criminalistics’ are done differently in Canada.
For instance, in the US, fibre evidence is still handled by the biology
section, whereas in Canada it is now handled by trace evidence or
forensic chemistry.
Forensic Toxicology. Forensic toxicologists identify and quantify
toxins (primarily drugs and alcohol, but also poisons) in body fluids
and in needles, pills, and so forth that may relate to a crime. They
also determine the physiological effects of such toxins on the
person. The analysis will determine, for instance, whether the dose
found in a body would kill or cause memory loss or impairment.
Trace Evidence or Forensic Chemistry. The RCMP lab system
has changed the name of forensic chemistry to trace evidence but
other lab systems still refer to it as chemistry. Forensic chemists
analyze any non-biological substance found at a scene, such as
paint, fibre, glue, drywall, gasoline, and bomb components. They
are the main scientists involved in hit and run, break and enter,
arson, and terrorist crimes. This is the equivalent to the physical
science unit that Saferstein refers to in US labs.
Firearms and Tool marks. Firearms specialists compare tool
marks and firearms to determine whether a tool made a certain
mark; for example, whether a chisel was used to break open a door
or whether a gun fired a specific bullet.
Questioned Documents. Questioned documents examiners look
primarily at handwriting to determine whether a person wrote a
suspect document. They also look at documents to see whether
they have been altered, and they look at machines like fax
machines and printers that produce writing.
Each unit employs a number of forensic scientists, but it also has
technicians. They assist scientists and run part or all of the chemical
analyses. However, the scientists oversee the work, perform the
interpretations, and write the reports, and they may eventually testify in
court. (To read more on careers in these and other forensic fields, go to
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