Forensic Science Unit



Adult Learning Program: Science IV

Forensic Science – Optional Module (4 – 6 weeks)

Start Date:

Anticipated Finish Date: ______________Actual: _______________________

|Area |To do |Value |Actual Mark |

|Labs |Paper Chromatography & Handwriting Analysis |10 | |

|(You must complete a minimum | | | |

|of 4) | | | |

| |Hair and Fiber Analysis |10 | |

| |Blood Typing |10 | |

| |Fingerprinting |10 | |

| |Fingerprinting: Multiple Methods |10 | |

|Documentary |Bugs, Bones & Botany - questions |10 | |

|Case Study |Crime Scene Investigation |30 | |

|Test |Based on lab work and theory from module |20 | |

CLASS SCHEDULE – If you have chosen this module, then you have committed to attending all classes and labs. We will move through this module as a group. If you miss a lab in your scheduled time, it is your responsibility to make it up in the other time slot. The only flexibility of time is in the writing of the test, though you are encouraged to have taken this test no later than _____________.

In the event that the weather plays havoc on the schedule, a new schedule will be developed and circulated.

Table of Contents

Introduction 3

Learning Outcomes 3

History of Forensic Science 4

Firearms and Toolmark Identification 5

Document Analysis 6

Explosives – Fires & Bombs 9

Microscopy in Forensics 11

Blood Analysis 13

DNA Analysis 15

Fingerprinting 17

Blood Splatter / Bloodstain 19

Other Testing Methods 19

Resources 23

Introduction

People working in the field of Forensic Science use scientific knowledge and apply scientific theories to help them to solve crimes. Forensics draws from many disciplines of science. Blood grouping, DNA fingerprinting, chromatography, chemical analysis of various substances, microscopic observation, entomology and radioactive dating are a few of the techniques used to prove when, where, how and by whom a crime is committed. This unit will help you to understand how concepts from science, particularly those from biology and chemistry, are useful to scientists and investigators in the course of their work.

Learning Outcomes

After completing this unit, you should be able to

← Define Forensic Science.

← Examine the history of forensic science, noting important developments.

← Explain the connection between developments in technology and developments in forensics.

← Describe the operation of a variety of testing methods in forensics

← Understand and explain the role of DNA analysis in forensic science.

← Understand and explain the importance of microscopy in Forensic science.

← Compile and interpret pieces of evidence to solve a simple crime.

← Administer a fingerprinting process and identify fingerprint patterns

← Compare methods of explosives detection.

NOTE:

There will be a number of lectures explaining information in this module. A schedule of these lectures will be posted. It will be very helpful to you to attend these lectures as they will review the lab procedure the day before the lab takes place and will give you the opportunity to ask questions concerning any information in the module you do not understand or find confusing. Labs are scheduled and under regular circumstances, will not be repeated. The case study day is 30% of your mark for this module and has only be repeated in the same year once – this was because of a Metro Transit Strike.

Excellent attendance is critical to successfully completing this module. If daily attendance is problematic for you, you may wish to consider completing an alternate module as one of your elective modules.

History of Forensic Science

In Canada

Prior to 1953, efforts in forensic science in Canada generally occurred independently of each other. News of progress in the area was usually heard through the media.

It wasn't until October 16, 1953, that seventeen people interested in developing the field met in Ottawa to form the Canadian Society of Forensic Science. These people were led by RCMP firearms identification expert Inspector James Churchman, and chemist Dr. Charles Farmilo with the Department of National Health and Welfare. Beginning in 1963 the society began to publish a newsletter. Then in 1968, the society began publication of the Canadian Society of Forensic Science Journal. Today membership is over 450. For more information on the beginnings of this society and its founding members, see your teacher for a supplemental reading.

The first forensic laboratory in North America, the Institut de médecine légale et de police Scientifique, was established in Montreal by Wilfred Dérôme in 1914. In the early twenties, this laboratory developed a method of determining the alcohol content of blood. The method was problematic, and had to be modified so many times that the event went unappreciated for its historical significance. The Institut gained more recognition from outside the country than from within Quebec and Canada. In 1922, Dr. Rosario Fontaine, graduate of a diploma in legal medicine from University of Paris, joined the Institut.

In 1932, the government of Ontario hired Dr. E. R. Frankish to organize and operate a laboratory that would perform autopsies, blood tests, and the examination and analysis of seminal stains, hairs, fibers, and plant materials. Blood and urine analyses were added later.

Other Milestones

The first record of a print being involved in a crime was in the year 1000 BC. A Roman attorney showed that a palm print was used to frame a person for murder.

The 1880s saw the development of fingerprint identification. This would soon become a key in forensic crime-solving for investigators. In 1823 the first classification of fingerprints was established by a Prussian, Johannes Purkinje. In 1880 Scottish physician Henry Faulds used powders to increase the visibility of fingerprints, and this became common practice in solving crimes.

In 1901 a new classification of fingerprinting was developed as a revision of the previous system. This work was completed by Sir Edward Henry of Scotland Yard. 1903 saw fingerprints identifying which individual out of a set of twins was guilty of the crime. In 1964, Scotland Yard’s Fingerprint Bureau started the computerization of the nation’s fingerprints.

Throughout this document you will note other milestone developments in forensic science. The two websites and

also provide links to other information on the history of forensic science.

Firearms and Toolmark Identification

Investigators must look closely at the "tools" of crime if they are to verify that they have been used. Firearms and toolmark identification involves determining what make of gun, other type of weapon or type of explosive was used in the crime being studied. As well, they look at imprint evidence. In all cases the use of microscopes is critical to establishing solid evidence.

Bullet Matching

When firearms are made, they undergo a process called rifling. The purpose of rifling is to cause the bullet to spin as it passes out of the barrel of the firearm. This spin enables the bullet to travel in a straight line. Rifling is a series of ridges (called lands) and grooves (called groves) along the inside of the gun barrel. As the bullet passes out of the barrel these lands and groves place microscopic marks on the bullet. The bullet can be scarred in this way because it is made of lead. Lead is a soft metal, and becomes softer as a result of the heat generated inside the gun when it is fired. As well, friction occurs when the bullet passes through the barrel.

Each firearm creates unique markings (much like human fingerprints) on the bullets fired from it. Because of this, scientists can match a spent bullet with a particular gun. A new bullet can be fired from the gun, and the two bullets can then be compared under a microscope. If after complete rotation of the two bullets, the scientists are unable to perfectly match the bullet markings they know that gun found was not the one used in the crime.

Imprint Analysis

Forensic investigators survey the scene of the crime for their clues. They comb all surfaces for any imprints that may have been left by criminals. Imprints used as forensic science evidence are of two types: two-dimensional (2-D) or three-dimensional (3-D).

2-D imprints are formed when an object passes through a substance and removes some of the substance leaving a negative image of the object. This process can also leave a 2-D imprint on another substance. One example that could happen at a crime would be if one person stabs another and steps in the blood that is spilt. The offender will leave 2-D imprints in the blood (negative image) and also across the floor or street where he/she walks after stepping in the blood.

3-D imprints are left in substances such as mud, wet concrete or plaster. In this situation, the object pushes into the imaging substance and leaves an image that includes the surface relief (bumps and hollows, tread pattern and wear, etc.) of the object. As the imaging substance (mud, wet plaster, etc.) dries, the image of the object remains. The unique wear patterns on tires and footwear can then be used to identify the vehicle / person who made the print.

Toolmark Identification

It is possible for crime investigators to identify the actual tool that was used in a crime (not just the make or model) from the markings it leaves. If a detective sees that a screwdriver was used to gain unlawful entry into a building, he or she knows that the marks it leaves on the lock or doorway are unique to that screwdriver. The manner in which the tool scraped the surface and /or its defects may not be easily distinguished by the naked eye, but will be visible and identifiable under microscopic examination.

Document Analysis

This branch of forensic science uses the knowledge of experts in several areas. Some of those areas are handwriting analysis, typewriting analysis, paper analysis, counterfeiting, forgery, computer print-out and diskette analysis, ink analysis and document dating.

Handwriting Analysis

Handwriting analysis involves painstaking examination of the design, shape and structure of handwriting to determine authorship of a given handwriting sample.   The basic principle underlying this type of analysis is that no two people write the exact same thing in the exact same way.    Every person develops unique peculiarities and characteristics in their handwriting.

Handwriting analysts must examine a number of characteristics of the words written. These characteristics include letter formations, connecting strokes between the letters, upstrokes, retraces, down strokes, spacing, baseline, curves, size, distortions and hesitations.  By examining these details and variations in a questioned sample and comparing them to a sample of known authorship, they can determine whether or not the authorship is genuine. Experts use magnifying lenses and microscopes to examine the subtle differences in handwriting samples – especially when dealing with a people highly skilled in forgery. Accurate and precise measurement is key to the success of this analysis. 

You should note that this type of handwriting analysis is not to be confused with studying handwriting to determine someone's personality traits. This type of study of handwriting is not considered true science by those in the forensics field but can also be considered when trying to gather information on the personality and mental attitude of a suspect.

Ink Analysis

When examining documents such as a ransom note, crime investigators will analyze the ink. All inks are not equal. Though we are able to distinguish one blue ink from another by looking at it, a forensic scientist is able to tell more. The scientist is actually able to distinguish one ink source from another. One method of analyzing ink is through a method known as ink chromatography.

Ink is a mixture of several colors used to produce one. Chromatography is a method used to separate and identify parts of a mixture. Using chromatography, the colors in ink can be separated.

If ink is exposed to certain liquids called solvents, the colors will dissolve and separate within the liquid. If the solution is then allowed to soak into a piece of chromatography paper, the different colors will create bands on the paper. They will remain in solution.

Inks of the same type will always produce the same banding pattern when this technique is used. The bands are created because the different components of the ink dissolve differently in the solvent used. This is referred to as the ink's solubility.

The greater the solubility of the ink for the solvent, the further up on the paper the band will appear. The higher band results because the ink component stays dissolved in the solvent for a longer period of time than other components, and travels further up the paper. The resultant paper with bands on it is called a chromatograph.

Chromatography is a scientific concept that allows a crime investigator to uncover information that would be missed by the naked and untrained eye.

See diagram below for a sample of a typical paper chromatograph.

Typical Paper Chromatograph

[pic]

Complete Lab 1: Ink and Paper Chromatography

Typewriters

As with other types of tools, all typewriters of a particular make and model are very much the same. However, with time and use, individual models develop defects that translate to paper when the machine is used.  These defects on the typed page can be matched back to the typewriter that was used to create it.  

These defects in the typeface are revealed in a number of ways.  If the type bar (the bar on which the letter element is attached and hammered down to the page) is bent, the letter is misaligned or 'off its feet.'  Misalignments can also cause an area of a specific letter not to print, such as the loop on the bottom of a 'g.'  The letter can be misaligned or damaged horizontally or vertically.  Small lumps of plastic can adhere to the type key during manufacture and are made permanent by the coating process.  This defect is called 'flashing.'  As wear and tear increases, the defects become more exaggerated.

Printers

As with the typewriter, printers of the same make and model produce printouts that appear identical. Closer examination of these documents, however, will show that each individual computer printer produces a document unique to it.

Laser printers produce a document by burning carbon toner (powder) onto the paper. The paper is rolled over a barrel to produce this image. With wear on the barrel, the barrel will develop markings unique to itself. For example, while performing regular maintenance on the barrel a technician may accidently create a small groove in the barrel. Any characters that come in contact with that part of the barrel will have an image that is slightly distorted.

Inkjet printers create documents by spraying ink onto the paper. Again with wear and tear - perhaps the results of maintenance and rough use - the printer will develop unique quirks. The wear and tear may result in the spraying mechanism being slightly damaged. The mechanism is still able to function but may not create characters that are as perfectly shaped as they were when new.

Dot matrix printers have hammers that strike an inked ribbon that strikes the paper to create an image. The hammer creates a small dot on the paper and creates characters by grouping the dots together. As the printer is used the hammers will develop patterns unique to the printer. Close examination of the dots will reveal that not all are perfectly round as they were in the beginning.

Analyzing the printout will tell investigators what type of computer printer has been used - laser, inkjet or dot matrix. Analyzing the ink will tell investigators what type of printer they are searching for. Different manufacturers use different ink compositions. This is particularly useful for inkjet printers.

Explosives – Fires & Bombs

If an investigator proves that arson has been committed, the chances are that the fire was set by the criminal as a way of destroying property or murdering someone. However, fires may also be the result of accidents. When fire inspectors investigate a fire, often the first thing they need to do is to determine if the fire was an accident, or deliberately set.

Fire (burin) is a chemical reaction. It is known as combustion – the chemical combination of a substance with oxygen. All elements have a characteristic flame colour when they burn. In chemistry it is referred to as a flame test. Some compounds also produce characteristic colours of flames and smoke. For example, if a fire has started because some cooking has ignited, the flames will be yellow and the smoke brown. On the other hand, if the cause of the fire has been gasoline the flames will be yellow or white with black smoke. Compounds are not as specific in their flame colour as are elements, but knowing the colour of the flame and smoke is useful to investigators. This information can help them narrow their search for the cause of the fire.

If the fire being investigated is the result of arson, one sign that points to this is the presence of more than one starting point for the fire. The starting point for a fire is called the seat of a fire.

Other indicators of arson are the presence of accelerants, piles of flammable materials, a fuse or timing device. One problem investigators run into when trying to detect accelerants is the presence of carpet in the area that has been burned. When some types of carpet burn they give off by-products that are very similar to some common accelerants. For this reason, any unburned carpet samples at the site will be taken back to the lab and burned to analyze any by-products.

There are two broad categories of accelerants – petroleum distillates and non-petroleum accelerants. The most common of the petroleum accelerants are gasoline and kerosene. Common non-petroleum accelerants are turpentine, lubricants and alcohol.

Investigators attempting to identify the accelerant investigators often use dogs – particularly the Labrador Retriever. This breed of dog has the most sensitive sense of smell of all dogs. The dog is trained to detect the smell of several common accelerants. For more information on this topic you may wish to consult the website .

Another method fire investigators use to detect accelerants is to use ultraviolet light. When exposed to UV light, petroleum-based accelerants will glow.

Another concern when it has been determined that the fire being investigated is the result of arson is the reason for the arson. If a body is found in the ruins of the fire, investigators must then determine if the person was killed before the fire was lit, or if they died as a result of the fire. This is generally determined during an autopsy.

Forensic scientists analyze samples of the victim’s blood and lungs using a microscope. If soot is discovered in the lungs, the conclusion is that the victim was alive and inhaled smoke when the fire began to burn. Similarly, if the blood is found to contain higher than normal concentration of carbon monoxide, this too suggests the body was alive when the fire was started.

Burning rarely occurs to the degree that would conceal other injuries to the body. If a wound was inflicted on a person previous to the burning, there will be a mass of white blood cells evident at the site of the wound. This indicates the body was already in the process of trying to ward off infection from the injury. These white blood cells will blister when burned. In contrast, burns on a body that is dead before the burning will be hard and yellow. When scientists use methods of detecting poisons and drugs (as described below) a burned body is still able to disclose if it was poisoned.

Microscopy in Forensics

Microscopes continue to be one of the most important tools in forensics. Various types of microscopes are used in various types of analyses.

Light Microscope

This microscope uses the visible light spectrum for its illumination source. The use of lenses enables the examiner to magnify the specimen up to 1500 times its size. This type of microscope is useful in examining hair fiber and bullet samples. Cameras are mounted to the eyepiece of light microscope to gather a permanent image of the sample.

Electron Microscopes

There are two types of electron microscopes – transmission and scanning. Both types of electron microscopes use a beam of excited electrons for their illumination source.

In the transmission electron microscope (TEM), the beam of electrons passes through the specimen.

The scanning electron microscope (SEM) passes the beam of electrons over the surface of the specimen. An electron gun at the top of the SEM chamber generates a beam of activated electrons. This beam passes down the chamber and is focused on the specimen using magnets. The beam then scans back and forth over the object. As the beam passes over the object, some electrons are reflected back. These are called back-scattered electrons. An electron detector senses these reflected electrons and amplifies their reading to generate an image. The image may then be produced on a monitor or photographic film.

Magnification with a SEM can be up to 100, 000 X and can also provide information about the elements that are present in the sample being examined. Because of its ability to provide information about the elements composing a substance, the SEM is a useful tool when analyzing paint samples, gunpowder residue, other types of explosives, soil samples and any other substances found at a scene that are foreign to that scene.

For an online demonstration of how the SEM works, check with a web site such as: , , or perform your own search using the words “Scanning Electron Microscope.”

Hair and Fiber Analysis

Scientists first examine hair with a microscope to decide if the hair is human or animal. To the naked eye, a long blonde hair from a golden retriever or one from its owner can look very much alike.

To determine if the hair is human or animal, the forensic examiner will pay attention to the outer-most layer of the hair – the cuticle. The cuticle has scales that overlap. These scales allow the examiner to determine the species to which the hair belongs.

Inside to the cuticle is the cortex. This layer contains the pigment molecules that will give the hair its colour. Arrangement of pigmentation within the cortex differs from one person to the next. By examining this, the investigator can tell if the person has chemically coloured their hair.

The very centre of the shaft is known as the medulla. This part of the hair is also important when determining species.

Examination of hair can help in establishing the racial group of an individual, or their approximate age. Adult hair is much coarser than children's hair. Without attached follicle tissue (the white bulb attached to the root when a hair is pulled out), it is not possible to perform DNA analysis on a hair sample.

Hair analysis can prove helpful in solving crimes because hair can contain poison residue if the body has been subjected to poisoning. Also, traces of dirt can help investigators identify the location of a crime if the sample in the hair is not characteristic of the area in which the victim is found.

There is some variation in different hairs from the same person. Investigators prefer to use a number of hairs as opposed to a single hair for this reason.

Fibers are the smallest unit of a textile material. Fibers are useful as they are often able to establish the presence of another person at a crime scene. They have also been useful in establishing the location of the crime when the body has been moved.

Scientists examine fibers under a microscope in the hope of discovering a unique characteristic of that fiber. This may be a particular pattern of the dyeing process, twisting patterns, or some unusual shape to the fiber. The presence of a characteristic unique to the fiber is the benefit of using fibers in crime solving. The uniqueness of the fiber helps to establish (or dispute) the connection between the suspect and the crime.

Complete Lab 2: Hair and Fiber

Blood Analysis

The basic level of blood analysis will involve determining the types of blood present. Blood type is an inherited characteristic. A person may have either type A, B, AB or O. The protein(s) that determines if a person has type A, B, AB or O will be present or absent in the red blood cells (RBC).

Each gene (location) for a characteristic found on one of the 46 chromosomes present in the human cell can have a different form. The form of the gene is known as the allele. For some characteristics or traits there are just two forms of the gene; for others there may be more than two. The gene for blood type in humans has three alleles – LA, LB, LO.

The LA allele will code for the person to produce antigen A on the surface of their RBC. The LB allele will code for the person to produce antigen B on the surface of their RBC. The LO allele will code for the person to not produce antigens on the surface of their RBC. The table below shows the possible combinations of genes a person may have, known as the genotype, and the resulting blood type.

|Allele from |Allele from |Child’s |Child’s |

|Mother |Father |Genotype |Blood Type |

|LA |LA |LA LA |A |

|LA |LB |LA LB |AB |

|LA |LO |LA LO |A |

|LB |LA |LA LB |AB |

|LB |LB |LB LB |B |

|LB |LO |LB LO |B |

|LO |LO |LO LO |O |

From the table you can see that there is more than one possible combination of genes for the same blood type. When a person has an allele that results in the production of A antigen on the surface of their RBC, the person will have type A blood if the second allele is an A or an O. This is because the allele for A (and B) is dominant over the allele for O. Dominance in genetics can be thought of as the allele being more powerful, as black pigment in paint is more powerful than white – you can never add enough white pigment to black paint to make it white. In the case of the allele for A antigens and B antigens neither is dominant over the other, thus the blood type AB. The allele for type A and the allele for type B are said to be codominant. Each is as strong as the other.

The dominance or recessiveness (opposite of dominance) of an allele does not indicate that one of the traits is necessarily better than the other. It simply means that one form is able to overshadow the other.

In addition to generating the coded antigen, blood also contains antibodies for the protein the person is not coded to produce. The table below summarizes the blood type of a person and the antibodies present in their blood for blood type proteins.

|Blood |Proteins |Antibodies |

|Type |Present |Present |

|A |A |B |

|B |B |A |

|AB |A, B |None |

|O |none |A, B |

An antibody is a blood component that is able to ingest and destroy a foreign substance or organism. Thus type O blood will see the presence of type A and / or type B proteins as being foreign material and attempt to destroy these proteins. This is the basis for blood typing.

To determine a blood type a small sample of blood is needed. After the blood sample has been obtained, a drop or two is placed on two microscope slides. One is then mixed with anti-A and the other is mixed with anti-B solutions – the anti-A and anti-B antibodies. If the blood mixed with the anti-A solution clumps (coagulates) then the person has type A blood. The anti-A antibodies in the solution attacked the A proteins on the RBC surfaces and tried to destroy them. The diagram below shows various results expected from this type of blood testing.

BLOOD TYPING

Anti-A solution Anti-B solution Blood Type

[pic]

Establishing the blood type of the person who committed the crime helps to narrow the field of suspects.

Complete Lab 3: Blood Typing

DNA Analysis

DNA analysis is also referred to as “DNA Fingerprinting”. This technique was developed in 1980 by Dr. Ray White, and DNA evidence was first used to convict a criminal in 1987. This is a useful method of determining who committed a crime since a person’s DNA is as unique to a person as their fingerprints. Identical twins are the exception – their DNA is the same, but their fingerprints are different. The criminal’s DNA is more likely to be found at the crime scene than are his or her fingerprints.

DNA is found in all cells of a person. Therefore, if a hair, a spot of blood, skin scrapings from underneath the victim’s nails, or other sample from the criminal is recovered from the crime scene, a definite identification of the criminal can be made.

DNA is an abbreviation for deoxyribonucleic acid. This is the material carrying our genetic code. DNA resembles a twisted ladder. DNA is made from a number of smaller molecules bonded together. There is a sugar molecule deoxyribose, a phosphate group from phosphoric acid and a nitrogenous base. The nitrogenous base may be guanine, thymine, adenine, or cytosine. The diagrams below show the structure of these components of DNA.

The deoxyribose and the phosphate groups join to form the sides of the ladder with the nitrogenous bases forming the rungs by joining together through the attraction of hydrogen bonds. A hydrogen bond is the attraction of a hydrogen atom in one molecule to a fluorine, nitrogen or oxygen in another molecule. The molecules involved in the hydrogen bond are polar molecules. The diagram below shows the joining of phosphoric acid with deoxyribose.

The phosphate –deoxyribose complex joins with the nitrogenous bases to form nucleotides. The diagram below shows a nucleotide formed from the joining of thymine, deoxyribose, and phosphoric acid.

The nitrogenous base nucleotides pair in specific combinations – adenine pairs only with thymine and cytosine pairs only with guanine. The diagram below is a schematic representation of an untwisted strand of DNA.

| | | | | |

| | | | | |

| | | | | |

| | | | | |

| | | | | |

| | | | | |

| | | | | |

| | | | | |

| | | | | |

| | | | | |

| | | | | |

| | | | | |

| | | | | |

| | | | | |

| | | | | |

| | | | | |

| | | | | |

For animated presentation of this information search the Internet using the keywords “DNA”+ "Fingerprinting” or check out a site such as .

Fingerprinting

As noted above, except for identical twins, everyone has unique DNA. Everyone has unique fingerprints – even identical twins. There are central banks of fingerprints in the USA and Canada as well as in other parts of the world. There are four basic groups of fingerprint patterns: arch, whorl, loops and composites (a mixture of two of the other patterns). Each of these groups has subgroups. For diagrams of these patterns, check with your teacher or a website such as or or perform your own search using keywords “Fingerprint Patterns”.

The process of taking fingerprints from fingers is relatively simple. Each finger is given a number one to five starting with the right thumb, and then six to ten starting with the left thumb. Each finger is coated with ink and then pressed on to a “ten-card” in the appropriately numbered box on the card. When pressing the fingers it is important to roll the finger from one edge to the other. In addition to the fingerprints, name, aliases, date of birth, size of hand, shape of palm, eye colour and other relevant types of information are included on a fingerprint card. For a sample of fingerprint cards used today contact your local law enforcement or child find office.

Our bodies contain amino acids – building block molecules. Amino acids contain long chains of carbon and hydrogen atoms joined together as well as an amino (nitrogen / hydrogen) group and a carboxylic acid group. The diagram below shows the structure of a simple amino acid – glycine.

[pic]

Our bodies also produce perspiration by nature of our metabolism. Metabolism is the continual breaking down of fuel molecules, mainly glucose, and building of other materials – for example hair, nails and skin. When our amino acids combine with our sweat and we touch something, an image of our fingerprint is transferred to the object we touched. This type of fingerprint is known as a latent print (not ordinarily visible to the eye).

Investigators currently use a variety of methods for making latent prints visible. The easiest latent prints to develop are those left on nonporous surfaces. The first method used to retrieve these prints involved a gray-black dusting powder. This method is still used today. It is most effective when the prints are fresh – the natural oils have not had time to dry. The powder is gently brushed on with a soft brush and then excess is blown away. The resulting images are photographed and also lifted with a special tape. The tape is then applied to a ten-card to preserve the print. One disadvantage to using gray-black powder is trying to reveal prints on similarly coloured surfaces. Today other colours of powders are available for use. Some powders have the ability to glow under UV light.

Fuming is another method of obtaining latent fingerprints. In fuming, a chemical that vaporizes easily is exposed to an item the investigators suspect to have latent fingerprints. The chemical is able to chemically bond to the amino acids in the fingerprint thereby emphasizing the print and making it possible to be photographed or lifted. Fuming with super glue (cyanoacrylate) was discovered by accident when a British police officer used some of the glue to fix a broken heater and realized how the prints on the heater became visible. Normally fuming is done in a lab in an enclosed area. However, Super Glue permits items that cannot be transported back to the forensic lab to be checked for prints at the scene. After prints become visible using fuming, powder may be used on the print so that it may then be lifted.

Though not the last, another important method of obtaining latent prints is vacuum metal deposition (VMD). This method of fingerprint detection is expensive but will often work where others have failed – even on surfaces that have been submerged in water. The machine used exposes the fingerprint to gold vapours in a vacuum. The gold is absorbed into the oils present in the print. The gold-coated print is then exposed to zinc, which in turn bonds to any gold that has stuck to the print area. In 1989, the RCMP was the only organization in North America to own this technology.

Complete Lab 4: Fingerprint Analysis and

Lab 5: Multiple Methods of Fingerprinting

Blood Splatter / Bloodstain

Anytime blood is present at a crime scene, the crime is considered to have been violent. As you have learned earlier in this unit, from a sample of blood suspects can be eliminated or confirmed. In this section, you will learn how the patterns of blood found at a crime scene can inform investigators about the events of the crime, the weapon(s) used and the movement of those involved. More information on blood splatters and bloodstains will be presented in class.

Other Testing Methods

There are many other methods of testing and gathering evidence in the world of forensic science. Some others that we will examine are spectrometry, atomic absorption spectrometry, breathalyzer, drug testing, gas liquid chromatography and the polygraph.

Spectrometry

Spectrometry is the study of spectra for atomic and molecular structures. The spectrum of a substance is the range of energy emitted from the substance. The range is displayed in order according to wavelength. This is an effective means of identifying substances because all elements have a unique spectrum. Scientists use a spectrometer to examine substances by spectrometry. For an illustration of a spectrometer, perform an Internet search for the term or visit the web site acp.edu/facultystaff/genchem/GC2/lab/spectro/spec202.htm. This site shows a labelled diagram of a visible light spectrometer. Other models of spectrometers, though similar in design, are able to measure energy outside of the visible spectrum.

FT-IR

One type of spectrometer frequently used by those involved in forensics is the Fourier transform infrared spectrometer (FT-IR). The FT-IR has an infrared energy source which provides the energy to be absorbed by the unknown substance. After the substance has been hit by the IR energy, some of the energy will be absorbed and some will be reflected. The reflected energy is recorded by the detector inside the machine. The detector then produces a signal that is unique to that substance. A computer is then used to “visualize” the signal. The information concerning the signal is then compared to databases of spectra of known substances for the purpose of making a match. This method of substance identification is a quick and accurate means of identifying narcotics, bomb components or other materials. Your teacher has a short handout concerning more information on FT-IR.

Polygraph

The polygraph or lie detector is a testing procedure which most of us have heard about. It often is presented in movies and TV shows. There are many jurisdictions that will not accept polygraph tests as evidence. They are however often used as in conjunction with other pieces of information.

The person being questioned is connected to the polygraph machine with a number of connections

▪ Rubber tubes to the chest – measure respiration

▪ Blood pressure cuff on arm – measure blood pressure

▪ Metal plates on fingers – measure skin response

The person is asked some basic questions regarding their name, age, and address. The purpose of these simple, neutral questions is to establish a baseline for the subject. The machine records a mark on a paper when the subject answers each question. The theory is that the subject will not give false answers to these questions. This will inform the investigators of the subject’s normal blood pressure, skin temperature, respiration rate and skin moisture level under the questioning conditions.

When we are stressed our bodies generate uncontrolled physiological responses. This is the premise on which the polygraph is based. Once the baseline readings for the subject are established, the interviewer then continues with asking questions related to the crime being investigated. When telling lies, our bodies produce a greater physiological response then when we answer with the truth. The polygraph will record rises in the subject’s blood pressure, temperature, respiration rate, and perspiration on the skin. The results will indicate one of three things: the subject is truthful, the subject is deceptive, or the results are inconclusive.

The nerves that control the responses being measured by the polygraph are part of the autonomic nervous system. This section of our nervous system controls involuntary responses to our environment. The autonomic system in turn is divided into the sympathetic and parasympathetic systems. The sympathetic system prepares the body for increased activity. This is the system that is activated when we are stressed.

The nerves controlling the sympathetic system begin in the spinal cord and transmit their signals outward to their target organs. The stress of telling a lie stimulates the release of acetylcholine by certain nerves of the sympathetic system in the spinal cord. This chemical travels across as small gap known as a synapse to the dendrites of post- ganglionic nerves belonging to the sympathetic nervous system, and the system becomes activated. The impulse travels from the dendrites to the cell bodies and then down the axons to the nerve end bodies. The end bodies contain vesicles (sacs) containing another chemical messenger. The chemical messenger or neurotransmitter released by most sympathetic nerves is noradrenaline. This neurotransmitter will stimulate heart rates and respiration rates, as well as perspiration rate. A visit to the website will provide more detailed information on this topic if you are interested.

Authorities continue to debate the validity of a polygraph test. According to the American Polygraph Association, the test is valid. The problems encountered with the test are in the administration of the test. If the polygraph tester is not properly trained, the accuracy of the test will be jeopardized. The website sorrel.humboldt.edu/~klm28/polygraph.html is one site to consult to see a picture of a typical polygraph machine and a sample of its printout results.

Breathalyzer

The Breathalyzer was invented by Dr. Robert Borkenstein in 1954. It uses a breath sample to determine the level of alcohol in a person’s system. When a person drinks alcohol some of the alcohol is absorbed in the mouth, throat, stomach and intestines into the bloodstream. Once in the bloodstream, alcohol is able to travel to all parts of the body. When it reaches the brain and other parts of the central nervous system, alcohol acts as a depressant by slowing down the functioning of the nerves.

Alcohol is composed of a group of chemicals. The alcohol normally consumed is ethanol. Alcohol ingested through the mouth is able to enter the bloodstream unchanged. Ethanol is able to vaporize in the lungs, and some exits the body when we exhale. There is a relationship between the amount of alcohol in the blood and the amount in the breath. 2100 mL of air expelled from the lungs contains the same amount of alcohol as 1 mL of blood.

To determine the amount of alcohol in the breath, the subject breathes into a mouthpiece that is connected to the sample chamber. The sample is then bubbled through a vial containing sulfuric acid, potassium dichromate, silver nitrate and water. The purpose of each substance is

1. The sulfuric acid removes the alcohol from the air so that it dissolves in the water. Creates an acidic environment needed for the reaction to happen.

2. Potassium dichromate reacts with the alcohol in solution.

3. The silver nitrate acts as a catalyst.

4. Water is a solvent for the other reactants.

A catalyst is a substance that does not participate in a chemical reaction but makes it easier for the reaction to take place.

The chemical equation for the reaction is given below.

2 K2Cr2O7 + 3 CH3CH2OH + 8 H2SO4 → 2 Cr2(S04)3 + 3 CH3COOH + 11 H2O

|Potassium |Ethanol |Sulfuric Acid |Chromium Sulfate |Acetic acid |Water |

|dichromate | | | | | |

Potassium dichromate when dissolved in water is a reddish-orange. After the reaction has occurred and chromium sulfate is formed, the solution turns green. The degree of the color change is directly related to the concentration of the alcohol that was present in the solution.

Canine Units

Finally an old-fashioned and still very reliable means of detection of materials in luggage or on persons traveling, and for the detection of accelerants used in arson cases is the dog. Many airports have K-9 teams that are led through the airports by their law enforcement handlers (in uniform and plain clothes) sniffing for narcotics, explosives and other restricted items and materials.

Were you in class when Bugs, Bones, and Botany was shown? Have you completed the questions and submitted them? If you weren’t in class when the documentary was shown, see your instructor to find out how you can view it one your own.

When you have read and reviewed the information in this module, inform your instructor you are ready to write the test.

Resources

|csfs.ca/ |Canadian Forensic Society Web Page |

| |Information on DNA database in Canada, careers |

| |in forensics, history and online access to back |

| |issues of Canadian Forensic Journal |

|home.~thekeither/Forensic/forsone.htm |Web site explaining many issues related to |

| |Forensic Science in easy to understand language |

| |and terms |

|seahorse.louisiana.edu/cmps619 |Website providing diagrams of DNA and |

|/Pdf/Lect%202%20Sequences.pdf |explanations about the structure |

|biology.washington.edu/fingerprint/dnaintro.html |Website explaining one DNA fingerprinting |

| |process. |

|Ramsland, K. (2001). The Forensic Science of C.S.I. New York: Berkley Boulevard |Book discussing many aspects of solving crimes. |

|Books. |Case examples are given. |

|sln/SEM/works.html |Provides self-paced and automated presentation |

| |of how the SEM works. |

| |Website for the University of Technology Sydney |

| |Centre of Forensics. Links to many topics |

| |examined in this unit. |

|breathalyzer.htm/printable |Website explaining how the Breathalyzer works |

| |and links to other related sites. |

|Exhibit A – The Secrets of Forensic Science |Weekly series on Discovery channel which looks |

| |at the role forensic science plays in solving |

| |crimes. |

| |Search engine devoted to finding sites relating |

| |to forensics. |

-----------------------

Forensic Science Unit

Science IV: Optional Unit

[pic]

2016-17

Ink Spot

Intermediate

End solvent line

Separated ink components

A

B

AB

O

H2N

C

H

H

C

OH

O

Carboxylic acid group

'IJWXde~Œ¬ÊÏñò- " # $ < B O U d h i j Š ‹ òìæÛÓÈÛ¿¶ª¶¡˜?‹„x?l?x?x?x?lcZNhàT`hQ25?CJaJhQ25?CJaJhàT`hQAmino group

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download