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Criminalistics An Introduction To Forensic Science 11th Edition by Saferstein – Test Bank
Chapter 5Death Investigation CHAPTER OVERVIEW <CR_SUM_BL_FIRST>• Forensic pathologists associated with the medical examiner’s or coroner’s office are responsible for determining the cause of an undetermined or unexpected death.</CR_SUM_BL_FIRST><CR_SUM_BL_MID>• Although both the coroner’s office and the medical examiner’s office are charged with investigating suspicious deaths, only the pathologist is trained to perform an autopsy. The tasks of examining the body for cause and manner of death and recording the results in the death certificate are all responsibilities of both offices.</CR_SUM_BL_MID><CR_SUM_BL_MID>• Protection of the body and the overall scene is of paramount importance, as is the ultimate removal of the body in a medically acceptable manner.</CR_SUM_BL_MID><CR_SUM_BL_MID>• An autopsy, in its broadest definition, is simply the examination of a body after death.</CR_SUM_BL_MID><CR_SUM_BL_MID>• The forensic autopsy consists of an external examination and an internal examination.</CR_SUM_BL_MID><CR_SUM_BL_MID>• The first steps taken for the external examination include a broad overview of the condition of the body and the clothing.</CR_SUM_BL_MID><CR_SUM_BL_MID>• The external examination also consists of classifying the injuries. This includes distinguishing between different types of wounds, such as a stab wound versus a gunshot wound.</CR_SUM_BL_MID><CR_SUM_BL_MID>• The dissection of the human body generally entails the removal of all internal organs through a Y-shaped incision beginning at the top of each shoulder and extending down to the pubic bone.</CR_SUM_BL_MID><CR_SUM_BL_MID>• The internal examination entails weighing, dissecting, and sectioning each organ of the body.</CR_SUM_BL_MID><CR_SUM_BL_MID>• Blood is often tested to determine the presence and levels of alcohol and drugs.</CR_SUM_BL_MID><CR_SUM_BL_MID>• Some drugs redistribute or reenter the blood after death and thus may complicate the interpretation of postmortem blood levels of these drugs.</CR_SUM_BL_MID><CR_SUM_BL_MID>• A primary objective of the autopsy is to determine the cause of death. The cause of death is defined as that which initiates the series of events ending in death.</CR_SUM_BL_MID><CR_SUM_BL_MID>• The most important determination in a violent death is the character of the injury that started the chain of events that resulted in death.</CR_SUM_BL_MID><CR_SUM_BL_MID>• Some of the more common causes of death are blunt force injury, sharp force injuries, asphyxia, gunshot wounds, and substance abuse.</CR_SUM_BL_MID><CR_SUM_BL_MID>• A blunt force injury is caused by a non-sharpened object such as a bat or pipe. A blunt force injury can abrade tissue or can cause a contusion arising from bleeding from tiny ruptured blood vessels within and beneath the skin.</CR_SUM_BL_MID><CR_SUM_BL_MID>• Sharp force injuries occur from weapons with sharp edges, such as knives or blades.</CR_SUM_BL_MID><CR_SUM_BL_MID>• Asphyxia encompasses a variety of conditions that involve interference with the intake of oxygen. For example, death at a fire scene is caused primarily by the extremely toxic gas carbon monoxide.</CR_SUM_BL_MID><CR_SUM_BL_MID>• Gunshot wounds originate from projectiles fired by a firearm. The distance a weapon was fired from a target is one of the most important factors in characterizing a gunshot wound.</CR_SUM_BL_MID><CR_SUM_BL_MID>• Because drug abuse is so common, a forensic pathologist will routinely order toxicological tests for the presence of drugs in nearly all autopsies.</CR_SUM_BL_MID><CR_SUM_BL_MID>• The manner in which death occurred is classified in death certifications as one of five categories: homicide, suicide, accidental, natural, or undetermined.</CR_SUM_BL_MID><CR_SUM_BL_MID>• Homicide is generally defined as a nonaccidental death resulting from grossly negligent, reckless, or intentional actions of another person.</CR_SUM_BL_MID><CR_SUM_BL_MID>• Suicide is the result of an individual taking his or her own life with lethal intention. Although drug abuse is deliberately committed by a victim, it is not considered a cause of suicide unless it was clearly intended as a lethal act.</CR_SUM_BL_MID><CR_SUM_BL_MID>• In all deaths that are ruled accidental, there must not be intent to cause harm through gross negligence on the part of a perpetrator or the victim. Traffic accidents make up a large percentage of accidental deaths, followed by drug overdoses and drownings.</CR_SUM_BL_MID><CR_SUM_BL_MID>• The classification of natural death includes disease and continual environmental abuse. This abuse can encompass various events, such as chronic drug and alcohol abuse or longtime exposure to natural toxins or asbestos.</CR_SUM_BL_MID><CR_SUM_BL_MID>• An undetermined cause of death arises when the cause of death cannot be determined by a physical finding at the autopsy, or because of the absence of meaningful findings in the subsequent toxicological and microscopic examinations.</CR_SUM_BL_MID><CR_SUM_BL_MID>• After death the body undergoes a process known as algor mortis, in which it will continually adjust to equalize with the environmental temperature.</CR_SUM_BL_MID><CR_SUM_BL_MID>• Another condition beginning when circulation ceases is livor mortis. When the human heart stops pumping, the blood begins to settle in the parts of the body closest to the ground. The skin appears bluish-purple in these areas.</CR_SUM_BL_MID><CR_SUM_BL_MID>• Immediately following death, a chemical change known as rigor mortis occurs in the muscles, causing them to become rigid.</CR_SUM_BL_MID><CR_SUM_BL_MID>• Another approach helpful for estimating the time of death is to measure potassium levels in the ocular fluid.</CR_SUM_BL_MID><CR_SUM_BL_MID>• The identification of food items in the stomach may help to determine the location of the decedent prior to death (i.e., during his or her last meal).</CR_SUM_BL_MID><CR_SUM_BL_MID>• Forensic anthropology is concerned primarily with the identification and examination of human skeletal remains.</CR_SUM_BL_MID><CR_SUM_BL_MID>• The gender of the decedent can be determined by the size and shape of various skeletal features, especially those in the pelvis and skull, or cranium.</CR_SUM_BL_MID><CR_SUM_BL_MID>• The height of the victim when alive can be estimated by measuring the long bones of the skeleton, especially those in the lower limbs.</CR_SUM_BL_MID><CR_SUM_BL_MID>• Forensic entomologists can approximate how long a body has been left exposed by examining the stage of development of the fly larvae on the body.</CR_SUM_BL_MID><CR_SUM_BL_MID>• Information about the arrival of other species of insects may also help determine the postmortem interval. The sequence of arrival of these groups depends mostly on the body’s natural decomposition process.</CR_SUM_BL_MID><CR_SUM_BL_LAST>• In general, insects first colonize the body’s naturally moist orifices. However, if open wounds are present, they will colonize there first.</CR_SUM_BL_LAST> LEARNING OBJECTIVES
- Describe the role of the forensic pathologist
- Describe the external, internal, and toxicology phases of an autopsy
- Distinguish cause and manner of death
- Describe common causes of death
- List various categories associated with the manner of death
- Describe chemical and physical changes helpful for estimating time of death
- Discuss the role of the forensic anthropologist in death investigation
- Describe the role of the forensic entomologist in death investigation
LECTURE OUTLINE ROLE OF THE FORENSIC PATHOLOGIST Scene Investigation The Autopsy Cause of Death Manner of Death Estimating Time of Death ROLE OF THE FORENSIC ANTHROPOLOGIST Recovering and Processing Remains Determining Victim Characteristics Other Contributions of Forensic Anthropology ROLE OF THE FORENSIC ENTOMOLOGIST Determining Time of Death Other Contributions of Forensic Entomology
- Teaching Note: Be sure to cover the key similarities and differences between the Forensic Pathologist, Forensic Anthropologist, and the Forensic Entomologist. It is a good idea to cover the blow fly life cycle and how many days each stage lasts.
List of Changes/Transition Guide Chapter 5, Death Investigations, is a new chapter that emphasizes the roles of the forensic pathologist, forensic anthropologist, and forensic entomologist in death investigation, paying particular attention to autopsy procedures and time of death determinations.</P></DIS></DISSET></CHAP> ADDITIONAL ASSIGNMENTS AND CLASS ACTIVITIES<DISSET><TTL>Demonstrations and Lecture-Starters</TTL><H1>Drawing Conclusions from Physical Evidence: Forensic Anthropology.</H1><DIS><P>Close observation of physical evidence helps forensic experts answer important questions during the investigation of a crime. Forensic anthropologists, who specialize in analyzing evidence of human remains, are sometimes asked to determine the sex of a victim from nothing more than scattered bones. This is typically accomplished by measuring the dimensions of certain bones such as the pelvis, which shows significant differences between the sexes. In this demonstration students are asked to use their observation and reasoning skills to determine the difference between male and female skeletons, then to use that knowledge to determine the sex of three unknown pelvises.<P>Provide the following information about two typical skeletons—one male and one female. The students will use this information to form conclusions about differences between the skeletons of each sex. (The sacrum is a bone that joins the two halves of the pelvic girdle at the top. Femur spread A is the distance between the upper leg bones about 2 inches below the hip joint. Femur spread B is the distance between the upper leg bones at a point about 2 inches below femur spread A.)</P>
|<UNTBL><COLHD><COLHD>Pelvic Width||Pelvic Opening||Sacrum Length||Sacrum Width||Femur Spread A||Femur </COLHD> Spread B</COLHD>|
<P>Following are the measurements of the unknown pelvises:</P>
|<UNTBL><COLHD><COLHD>Pelvic Width||Pelvic Opening||Sacrum Length||Sacrum Width||Femur Spread A||Femur</COLHD> Spread B</COLHD>|
<P>The students should draw the following conclusions from studying the “sample” pelvises:</P><BL><ITEM><P><INST>• </INST>The pelvic opening in the female is much wider in relation to its width than is the male pelvic opening.</P></ITEM><ITEM><P><INST>• </INST>The female sacrum is very wide in relation to its length; the length and width of the male sacrum are roughly equal.</P></ITEM><ITEM><P><INST>• </INST>The upper leg bones of the female bow inward from point A to B on the femur; the male leg bones do not bow inward.</P></ITEM></BL><P>Based on these observations, the student should conclude that pelvises A and C are female, while pelvis B is male.</P></DIS></DISSET></CHAP> Questions
- List items to be collected and sent to the forensic laboratory from an autopsy.
- Describe what’s entailed in an external examination during an autopsy.
- Describe what’s entailed in an internal examination during an autopsy.
- A primary objective of the autopsy is to determine the cause of death. Define the cause of death.</CR_SUM_BL_MID>
- Describe the characteristics of a blunt force injury.
- Describe the characteristics of a sharp force injury. </CR_SUM_BL_MID>
- Describe important factors in characterizing a gunshot wound.</CR_SUM_BL_MID>
- List the five categories of the manner of death. </CR_SUM_BL_MID>
- Distinguish between a homicide and a suicide.
- After death the body undergoes a process known as algor mortis. What is this? </CR_SUM_BL_MID>
- <CR_SUM_BL_MID>Another condition arising after death is livor mortis. What does this entail?
- Immediately following death, a chemical change known as rigor mortis occurs. Describe this phenomenon</CR_SUM_BL_MID>.
- <CR_SUM_BL_MID>Describe the approach for estimating the time of death by measuring potassium levels in the ocular fluid.</CR_SUM_BL_MID>
- What important considerations must be made when determining PMI using forensic entomology?
- List the areas of the skeleton that can be used to determine the gender of skeletal remains.
Answers to Questions
- Clothing, fingernail scrapings, head and pubic hair combings, buccal swab, vaginal, anal, and oral swabs, bullets, body area swabs, and hand swabs for gunshot residues.
- The first steps taken for the external examination include a broad overview of the condition of the body and the clothing. General characteristics of the body should be noted, including sex, height, weight, approximate age, color of hair, and physical condition. The presence of tattoos and scars, as well as puncture and track marks, are noted. <CHAP_BM>The external examination also consists of classifying the injuries. Hemorrhages in the eyelids (petechiae) are also essential to note. <H3><Char H31> </Char>
- Performing the internal examination entails weighing, dissecting, and sectioning each organ of the body. When required microscopic examination of the sectioned organs is conducted, this can help in determining the cause of death. Examination of the cranium requires cutting an incision from behind one ear to the other, peeling the scalp upward and backward, and sawing of the skull in a circular cut; then the skull cap is removed to reveal the brain. <CHAP_BM>
- The cause of death is that which initiates the series of events ending in death. The most important determination in a violent death is the character of the injury that started the chain of events that resulted in death.
- A blunt-force injury is caused by a non-sharpened object such a bat or pipe. A blunt-force injury can abrade, or scrape, tissue. If tissue is crushed by a blunt force to the point of causing skin to overstretch, a laceration will form, characterized by the skin splitting and tearing
- Sharp force injuries occur from weapons with sharp edges, such as knives or blades. These weapons are capable of cutting or stabbing. A <Char ITAL>cut</Char> is formed when the weapon produces an injury that is longer than it is deep. In contrast, a <Char ITAL>stab</Char> is deeper than its length. </H3>
- The appearance of the wound can be of help in estimating whether the firearm used to inflict the wound was discharged while in contact with the victim’s body or from a distance of only inches to many feet away. The investigator will compare powder residue distribution around the wound to test fires collected from the inflicting firearm to make this estimate.
- The manner of death relates to the circumstances that led to the fatal result. The manner of death is normally categorized as homicide, suicide, accident, natural, or undetermined.
- Generally the term <Char ITAL>homicide</Char> is defined as a nonaccidental death resulting from grossly negligent, reckless, or intentional actions of another person. Suicide is the result of an individual taking his or her own life with lethal intention. For a determination of suicide, it must be demonstrated that the individual carried out the act alone.
- The cooling of the body after death, or algor mortis, occurs at a predictable rate, enabling the pathologist to estimate time of death from the temperature of the body.
- The settling of blood in the parts of the body closest to the ground, known as livor mortis, creates a dark blue or purple appearance immediately and continues for up to 16 hours after death.
- Rigor mortis, or stiffening of the muscles, occurs within 24 hours of death and disappears within 36 hours.
- Time of death can also be estimated by measuring the concentration of potassium in the victim’s eye fluids, because cells in the eyeball release potassium at a predictable rate after death.
- The time required for stage development is affected by environmental influences such as geographical location, climate, weather conditions, and the presence of drugs. For example, cold temperatures hinder the development of fly eggs into adult flies. The forensic entomologist must consider these conditions when estimating the postmortem interval.
- The gender can be determined by observing the shape of the pelvis and sacrum, the size of the cranium, and the protrusion of the brow bone and mastoid process.
SUGGESTED ANSWERS TO END-OF-CHAPTER ASSIGNMENTS Review Questions
- Coroner and medical examiner
- Cause of death
- External and internal
- Stippling or tattooing
- Postmortem redistribution
- Carbon monoxide
- Algor mortis
- Livor mortis
- Autolysis and putrefaction
- Forensic anthropology
- Forensic entomology
Application and Critical Thinking
- Rigor mortis would be an unsuitable method if the victim had been dead longer than 36 hours because the condition disappears after this time. Livor mortis ceases approximately 16 hours after death, so it would be of limited value in estimating the time of death after this period elapsed. Algor mortis would not be an accurate method for estimating the time of death if the body was stored in a particularly hot or cold environment because extreme temperatures would affect the rate at which the body lost heat.
- a. A forensic entomologist
- A forensic odontologist
- A forensic anthropologist
- a. Homicide
- Natural causes
- Gender = Female
Ancestry = NegroidAge Range = 24-32 yearsHeight = 160.308 cm to 161.998 cm (approximately 63 inches or 5 ft 3 inches)
- D, B, F, C, A, E
Fingerprints CHAPTER OVERVIEW
- Fingerprints are a reproduction of friction skin ridges found on the palm side of the fingers and thumbs.
- The basic principles underlying the use of fingerprints in criminal investigations are as follows: (1) a fingerprint is an individual characteristic because no two fingers have yet been found to possess identical ridge characteristics; (2) a fingerprint remains unchanged during an individual’s lifetime; and (3) fingerprints have general ridge patterns that permit them to be systematically classified.
- All fingerprints are divided into three classes on the basis of their general pattern: loops, whorls, and arches.
- The individuality of a fingerprint is determined not by its general shape or pattern, but by a careful study of its ridge characteristics. The expert must demonstrate a point-by-point comparison in order to prove the identity of an individual.
- The FBI fingerprint database known as AFIS converts the image of a fingerprint into digital minutiae that contain data showing ridges at their points of termination (ridge endings) and their branching into two ridges (bifurcations).
- Visible prints are made when fingers touch a surface after the ridges have been in contact with a colored material such as blood, paint, grease, or ink.
- Plastic prints are ridge impressions left on a soft material, such as putty, wax, soap, or dust.
- When the finger touches a surface, perspiration and oils are transferred onto that surface, leaving a fingerprint. Prints deposited in this manner are invisible to the eye and are commonly referred to as latent or invisible fingerprints.
- Latent prints deposited on hard and nonabsorbent surfaces (such as glass, mirror, tile, and painted wood) are usually developed by the application of a powder, whereas prints on porous surfaces (such as papers and cardboard) generally require treatment with a chemical.
- Examiners use various chemical methods to visualize latent prints, such as iodine fuming, ninhydrin, and Physical Developer.
- Superglue fuming develops latent prints on nonporous surfaces, such as metals, electrical tape, leather, and plastic bags. Development occurs when fumes from the glue adhere to the print, usually producing a white latent print.
- Latent fingerprints are treated with chemicals that induce fluorescence when exposed to a high-intensity light or an alternate light source.
- Once a latent print has been visualized, it must be permanently preserved for future comparison and for possible use as court evidence. A photograph must be taken before any further attempts at preservation are made.
- If an object containing a fingerprint is small enough to be transported without destroying the print, it should be preserved in its entirety.
- Prints on large immovable objects that have been developed with a powder can best be preserved by “lifting” with a broad adhesive tape.
- Know the common ridge characteristics of a fingerprint
- List the three major fingerprint patterns and their respective subclasses
- Distinguish visible, plastic, and latent fingerprints
- Describe the concept of an automated fingerprint identification system (AFIS)
- List the techniques for developing latent fingerprints on porous and nonporous objects
- Describe the proper procedures for preserving a developed latent fingerprint
LECTURE OUTLINE HISTORY OF FINGERPRINTING Early Use of Fingerprints Early Classification of Fingerprints Adoption of Fingerprinting FUNDAMENTALS PRINCIPLES OF FINGERPRINTS First Principle: A Fingerprint is an Individual Characteristics; No Two Fingers Have Yet Been Found to Possess Identical Ridge Characteristics Second Principle: A Fingerprint Remains Unchanged During an Individual’s Lifetime Third Principle: Fingerprints Have General Ridge Patterns That Permit Them to Be Systematically Classified CLASSIFICATION OF FINGERPRINTS The Primary Classification AUTOMATED FINGERPRINT IDENTIFICATION SYSTEMS How AFIS Works Considerations with AFIS
- Teaching Note: Discuss the importance of having the fingerprint identified in the AFIS database to compare your sample fingerprint to. You could have a great fingerprint recovered at the scene but you have to have a known sample with known identity to actually match the print.
METHODS OF DETECTING FINGERPRINTS Locating Fingerprints Developing Latent Prints
- Teaching Note: It is essential to cover the various fingerprint powders and lighting methods used to develop prints.
PRESERVATION OF DEVELOPED PRINTS DIGITAL IMAGING FOR FINGERPRINT ENHANCEMENT Creating Digital Images Analyzing Digital Images List of Changes/Transition Guide Chapter 16 in the 10th edition has been moved to in the 11th edition. ADDITIONAL ASSIGNMENTS AND CLASS ACTIVITIES Virtual Forensics Lab The fingerprinting virtual laboratory exercise will review the methods of recording fingerprints, developing fingerprints, and comparing fingerprints. The student will use ink to record the fingerprints from a simulated hand. The student will use cyanoacrylate fuming to develop a simulated evidentiary fingerprint. Fingerprint patterns and ridge characteristics will be reviewed. Upon completion of the virtual laboratory exercise the student should be able to recognize and identify common fingerprint patterns and ridge characteristics. They should be able to use these patterns and characteristics to compare developed fingerprints to recorded fingerprints. Demonstrations and Lecture-Starters General Fingerprinting. MaterialsSeveral sheets of blank paperFingerprinting pad (if available) or ink padMagnifying glass ProcedureFingerprinting is perhaps the oldest method of scientific forensic identification. No two sets of same fingerprints are the same, yet they all exhibit characteristics that allow investigators to classify them for quicker identification. In this exercise, students should be matched up in teams of three. Each member of the group should roll the fingerprint of the right index finger of another group member onto a piece of paper. The paper should contain a print from every team member. Now, roll a print from each team member onto a separate blank piece of paper. Do NOT write the names of the team members on these papers. When the ink is dry, shuffle the papers and set two aside at random. Using the magnifying glass, each person on the team has 2 minutes to compare the unknown print to the named prints and determine who made it. Answer the following questions individually, then compare notes as a team and see if everyone agreed on the identity of the print. Follow-Up Questions
- Who do you believe made the unknown print?
- What is the general pattern of the print – arch, loop, or whorl?
- Did everyone in the team agree on the identity of the unknown print?
Latent Prints. Latent fingerprint development always proves to be a fun exercise. The following supplies can be purchased from police equipment suppliers such as Sirchie Finger Print Laboratories: BrushesBlack and gray latent powderNinhydrin sprayBlack and white hinge liftersTransparent tape Identifying Fingerprints: Superglue Fuming. In this demonstration, students will use the superglue fuming technique to identify questioned fingerprints. Before class, mount a lightbulb (or place a small lamp) in a clean aquarium. Cover the bulb or lamp with an aluminum can cut in half lengthwise. Seal the opening of the aquarium with a piece of wood or stiff cardboard cut to fit. At the beginning of class, distribute a clean glass slide to each student. Be sure to wear gloves when distributing the slides. Have each student label the slide with his or her name and make an impression of his or her right index finger on the slide. Collect the slides; remove the name labels from several of them; re-label them A, B, C, and so on; and place the slides in the aquarium. Now drop a little superglue on the can and turn on the lamp. In about 15 minutes you should see white prints begin to form on the slides. While the slides are fuming, make a fingerprint ID sheet for everyone in the class. To do so, have the students pair up in teams of two. Have one member of each pair turn a pencil sideways and rub a thick spot of graphite onto a piece of clear paper. The student should then roll his or her right index finger firmly from left to right in the graphite. Have the other member of the pair then place a piece of clear tape over the finger, gently remove the tape, and stick it to another clean sheet of paper. Label the print with the name of the student. Now each member of the pair reverses roles, so that you have a record of all of the students’ fingerprints. After the prints on the slides appear, remove the slides from the aquarium and allow students to examine them. Have them compare the prints on the slides to the class fingerprint record and ask them to identify the “suspect” prints on the slides. Also have students indicate whether each of the suspect prints is a loop, whorl, or arch pattern. After identifying the suspect prints, have students classify each of the fingerprints on the student record as either a loop, whorl, or arch, then calculate the percentage of each in the sample. Referring to the text, ask students how the percentages in the student sample compare with the population at large.</P></DIS> Questions
- Who published the first book on the science of fingerprinting? What were the book’s most important contributions to understanding fingerprints?
- What major advance in fingerprint technology was pioneered by Juan Vucetich and Sir Richard Henry? What was the importance of this advance?
- What aspect of a fingerprint determines its individuality?
- What is the dermal papillae and why is it important in fingerprinting?
- Why is it almost impossible to obscure one’s fingerprints by surgery or mutilation?
- Describe each of the three classes of fingerprints. Which class is the most common in the population? Which is least common?
- What aspect of a fingerprint forms the basis for primary classification under the FBI system? What is the main drawback of the FBI system?
- Briefly describe how the Automated Fingerprint Identification System (AFIS) creates a fingerprint image. What characteristics of the fingerprint does the AFIS record for comparison?
- What is the final step in fingerprint identification? Why is this step necessary if a computerized database of fingerprints is available to the forensic scientist?
- List and describe the three types of fingerprints that may be found at a crime scene.
- List two types of specialized fingerprint powders and name one advantage each has over traditional fingerprint powder.
- What is the most commonly used chemical method to visualize latent fingerprints on porous materials? If this method is unsuccessful, what other technique typically is used?
- What phenomenon underlies many of the new chemical techniques used to visualize latent fingerprints? Why is this phenomenon so valuable in fingerprint visualization?
- When should a fingerprint be “lifted” from a crime scene? Describe how to lift and preserve a fingerprint using adhesive tape.
- What is digital imaging and how is it used in fingerprint analysis? What is the greatest limitation to digital imaging?
Answers to Questions
- Francis Galton published the first book on the subject of fingerprinting. The book’s most important contributions were to demonstrate that no two prints are identical and that an individual’s prints remain unchanged from year to year.
- Vucetich and Henry pioneered the creation of classification systems capable of filing many thousands of prints in a logical and searchable sequence. This allowed law enforcement officials to quickly compare prints found at a crime scene to those of known criminals as an aid to identifying potential suspects.
- The identity, number, and relative location of ridge characteristics impart individuality to a fingerprint.
- The dermal papillae is a boundary of cells separating the outer portion of the skin (epidermis) and the inner skin (dermis). The shape of the dermal papillae determines the form and pattern of the ridges on the surface of the skin. Because the dermal papillae does not change shape throughout life, the ridge patterns of fingerprints also do not change.
- To obscure one’s fingerprint, an injury or surgery must reach deeply enough into the skin to damage the dermal papillae. Even so, it would be totally impossible to obliterate all of the ridge characteristics on the hand. Any attempt to do so would create deep scars that would provide new characteristics for identifying one’s prints.
- The three classes of fingerprints are loops, whorls, and arches. Loops are characterized by ridge lines that enter from one side of the pattern and curve around to exit from the same side of the pattern. Whorls include ridge patterns that are generally rounded or circular in shape and have two deltas. Arches are characterized by ridge lines that enter the print from one side and flow out the other side. Loops are most common; arches are least common.
- The presence or absence of the whorl pattern is the basis for determining the primary classification in the FBI system. The main drawback of the FBI system is that it is useful only when a full set of fingerprints is available.
- AFIS scans fingerprints and converts them into digital images that contain data on the relative location and orientation of ridge characteristics. The system records the points where ridges terminate, the points where they branch into two ridges, and the relative position and orientation of each ridge characteristic.
- The final step in fingerprint identification is always visual comparison of the prints in question by a trained examiner. A computer database can only produce a list of prints that are similar to the print in question; it cannot make a positive identification.
- Visible prints are made when a finger deposits a visible material such as ink, dirt, or blood onto a surface. Plastic prints are ridge impressions left on a soft material such as putty, wax, soap, or dust. Latent or invisible prints are impressions caused by the transfer of body perspiration or oils present on finger ridges to the surface of an object.
- Two specialized fingerprint powders are magnetic-sensitive powder and fluorescent powder. Using magnetic-sensitive powder offers less chance that the print will be destroyed or damaged because the powder is spread using a magnetic brush that has no bristles to come in contact with the surface containing the print. Fluorescent powders reveal a vivid image of a print under ultraviolet light. When the developing print is photographed under UV light, the color of the surface will not obscure the print.
- The ninhydrin method is most commonly used to visualize latent fingerprints on porous materials. If the ninhydrin method fails, the Physical Developer technique is typically used.
- The phenomenon of fluorescence serves as the underlying principle of many of the new chemical techniques used to visualize latent fingerprints. Substances that emit light or fluoresce are more readily seen either with the naked eye or through photography as compared to non-light-emitting materials. Thus, techniques based on fluorescence permit better visualization of all prints and allow the visualization of faint prints that other methods may fail to visualize.
- A print should be “lifted” from a crime scene when it is on a large, immovable object. One method of lifting is to dust the print with fingerprint powder, then cover the print with adhesive tape. When the tape is pulled up, the powder is transferred to the tape. Then the tape is placed on a card that provides a good background contrast with the powder.
- Digital imaging is a process through which a picture is converted into a series of square electronic dots known as pixels. It is used to compare fingerprints and to enhance poor fingerprint images. The main limitation of digital imaging is that it is only as useful as the images it has to work with. If the images are poor or incomplete, enhancement procedures will not work.
SUGGESTED ANSWERS TO END-OF-CHAPTER ASSIGNMENTS Review Questions
- Alphonse Bertillion
- Sir Edward Richard Henry
- Is not
- Ridge characteristics/minutae
- Dermal papillae
- Dermal papillae
- Loops; whorls; arches
- Type lines
- Plain whorl
- Plain arch
- Do not have
- Analysis, comparison, evaluation, and verification
- Visible fingerprint
- Latent fingerprints
- Physical developer
- Superglue fuming
- Alternate light sources
- Frequency Fourier transform analysis
Application and Critical Thinking
- a. Whorl
- The primary classification for this individual would be as follows:
0+8+4+0+116+8+0+2+1 Thus, the classification would be 13/27.
- a. Chemicals
- a. Scaling and resizing
- Spatial filtering
- Frequency analysis, or frequency Fourier transform (FFT)
Chapter 7The Microscope CHAPTER OVERVIEW
- A microscope is an optical instrument that uses a lens or a combination of lenses to magnify and resolve the fine details of an object.
- In the basic compound microscope, the object to be magnified is placed under the lower lens, called the objective lens, and the magnified image is viewed through the upper lens, known as the eyepiece lens.
- The comparison microscope consists of two independent objective lenses joined by an optical bridge to a common eyepiece lens. When a viewer looks through the eyepiece lens, the objects under investigation are observed side by side in a circular field that is equally divided into two parts.
- Modern firearms examination began with the introduction of the comparison microscope, which gives the examiner a side-by-side magnified view of bullets.
- The stereoscopic microscope consists of two monocular compound microscopes properly spaced and aligned to present a three-dimensional image of a specimen to the viewer, who looks through both eyepiece lenses.
- The large working distance of the stereoscopic microscope makes it ideal for microscopic examination of big, bulky items.
- Light that is confined to a single plane of vibration is said to be plane-polarized.
- The polarizing microscope made possible the examination of the interaction of plane-polarized light with matter.
- Polarizing microscopy is used to study birefringent materials, that is, materials that have a double refraction. Refractive-index data provides information that helps identify minerals present in a soil sample or the identity of a synthetic fiber.
- The microspectrophotometer is a spectrophotometer coupled with a light microscope. The device allows an examiner studying a specimen under the microscope to obtain the visible absorption spectrum or IR spectrum of the material being observed.
- The scanning electron microscope (SEM) bombards a specimen with a beam of electrons instead of light to produce a highly magnified image. This produces X-ray emissions that can be used to characterize elements present in the material under investigation.
- List and understand the parts of the compound microscope
- Define magnification, field of view, working distance, and depth of focus
- Contrast the comparison and compound microscopes
- Understand the theory and utility of the stereoscopic microscope
- Appreciate how a polarizing microscope is designed to characterize polarized light
- Appreciate how a microspectrophotometer can be used to examine trace physical evidence
- Compare and contrast the image formation mechanism of a light microscope to that of a scanning electron microscope
- Outline some forensic applications of the scanning electron microscope
LECTURE OUTLINE BASICS OF THE MICROSCOPE THE COMPOUND MICROSCOPE Parts of the Compound Microscope Properties of the Compound Microscope THE COMPARISON MICROSCOPE THE STEREOSCOPIC MICROSCOPE THE POLARIZING MICROSCOPE Polarization Applications of the Polarized Microscope THE MICROSPECTROPHOTOMETER THE SCANNING ELECTRON MICROSCOPE (SEM)
- Teaching Note: Emphasize that the microscope is one of the most important tools in the laboratory. Be sure to cover the uses for each type of microscope and why you would use that one over the other types available.
FORENSIC PALYNOLOGY: POLLEN AND SPORES AS EVIDENCE Classification of Spores and Pollen Analysis of Spores and Pollen List of Changes/Transition Guide Chapter 5, Death Investigations, is a new chapter that emphasizes the roles of the forensic pathologist, forensic anthropologist, and forensic entomologist in death investigation, paying particular attention to autopsy procedures and time of death determinations.</P></DIS></DISSET></CHAP>ADDITIONAL ASSIGNMENTS AND CLASS ACTIVITIES Demonstrations and Lecture-Starters Introduction to Microscopes. Because of the importance of the microscope to the crime laboratory, a criminalistics course must stress the use of these instruments. Each student should have access to compound and stereoscopic microscopes, and possibly a comparison microscope. The proper handling and care of the microscope are to be emphasized in the laboratory. Exercises demonstrating the magnifying power and depth of field of the microscope are most suitable for introducing the student to this instrument. Observing specimens such as tea and tobacco under the stereoscopic microscope allows the student to appreciate the stereo’s great depth of field. The student must also learn how to prepare dry-mount and wet-mount slides for examination under the compound microscope.Focusing the Microscope. Materials Compound light microscopePrepared slides Procedure The microscope is one of the most important tools in the laboratory. The first step in using the microscope is being able to focus on what you want to see. Take a prepared slide and place it on the stage, make sure to secure it in place with the stage clips. Always start with the low-power objective lens in place. Use the course adjustment knob (the larger knob) to bring the object into view. Once you can see the object use the fine adjustment knob (the smaller knob) to focus the item. If the slide needs to be adjusted many microscopes have stage adjustment knobs that will move the stage or slide, if your microscope does not you will have to manually move the slide. Once you have the object focused in the center of your view try to view the object in high power. To do this, move the high-power lens into place above the slide. Use the fine adjustment knob to focus the object; you should not have to use the course adjustment knob (doing so may break the slide). Follow-Up Questions
- To determine total magnification you multiply the objective lens power by the eyepiece lens power. What was the total magnification of your microscope when you were viewing the object in low power? What about in high power?
- Besides magnification, what did you observe about the real image (what your naked eye saw on the slide) compared to the virtual image (what you saw looking through the scope)?
- Did you observe anything when you moved the slide on the stage while looking through the scope?
Creating Wet Mount Slides. Materials Compound light microscopeSlide with cover slipWater with dropperSample object (example: hair, soil, thread, paper) Procedure To view some objects, it is better to create a wet mount slide. This helps to create a clearer view than a regular slide would allow. To create a wet mount slide, place the sample you want to view on the slide. Now place a drop of water on the sample. Take the cover slip and slowly cover the sample so that there are no air bubbles in the water; these would block your view of the sample. The slide is now ready to be viewed on the scope. Remember the steps to focus your slide. Follow-Up Questions
- After looking at the sample as a wet mount slide, create a regular slide with the same type of sample. Do you see a difference between the two types of slides and the images they produce?
- Other than the sample you viewed can you think of any other types of evidence that could be viewed using a wet mount slide?
- How does a magnifying glass enlarge objects viewed through it?
- What is the difference between a real image and a virtual image?
- Why does a compound microscope produce greater magnification than a magnifying glass? How does the eyepiece lens contribute to magnification?
- What is vertical illumination and under what conditions would a forensic scientist use it to examine a sample? Why is it superior to transmitted illumination under such conditions?
- How does one calculate the magnification power of a compound microscope?
- What does numerical aperture (N.A.) measure? What is the difference between a lens with N.A. 1.0 and one with N.A. 0.5?
- Why might an examiner choose a microscope with a lesser magnification to study a specimen?
- Briefly describe how a comparison microscope works and what it is used for.
- How did the comparison microscope make possible modern firearms examination?
- List two unique characteristics of the stereoscopic microscope.
- What is the most widely used microscope in the crime laboratory? What features make it particularly suited for examination of physical evidence?
- What happens to a light beam that passes through a polarizing crystal? What happens when plane-polarized light passes through a second polarizing crystal set perpendicular to the first crystal?
- What is the main advantage of the microspectrophotometer?
- Explain how the infrared microspectrophotometer determines the identity of a specimen. What type of physical evidence is the microspectrophotometer typically used to analyze?
- What is the basic difference between a scanning electron microscope and the other microscopes used in the crime laboratory?
- How can a scanning electron microscope be used to identify the elements present in a specimen?
- How can a scanning electron microscope be used to determine whether a suspect has recently fired a gun?
Answers to Questions
- A magnifying glass makes things appear larger by refracting, or bending, light rays as they pass from the air into the glass and back into the air.
- A real image is an image formed when light rays converge on a surface. An observer can see a real image with the naked eye. A virtual image cannot be seen directly, but only by an observer looking through a lens.
- A compound microscope produces greater magnification because it uses two lenses to enlarge the object being viewed instead of just one. The eyepiece lens magnifies the real, enlarged image created by the objective lens, producing a greatly enlarged virtual image of the object.
- Vertical illumination is illumination of a specimen from above. A forensic scientist would use vertical illumination when studying opaque specimens. Transmitted illumination can be used only with specimens that are transparent. With opaque specimens, the light source must be placed above the specimen and reflected off the specimen’s surface and into the lens.
- The total magnification power of a compound microscope is the product of the magnifying power of each lens.
- Numerical aperture measures the ability of an objective lens to resolve details into separate images instead of one blurred image. A lens with N.A. 1.0 can separate details at half the distance of a lens with N.A. 0.5.
- As magnifying power increases, the microscope’s field of view—the size of the specimen it can study—decreases. The microscope’s depth of focus—the thickness of the specimen it can study—also decreases with increasing magnification. An examiner might first select a lower-magnification microscope to get a good general overall view of the specimen, then switch later to a higher-power microscope to study smaller portions of the specimen in more detail.
- The comparison microscope is two compound microscopes connected by a bridge that uses mirrors and lenses to combine the images from two objective lenses into a single image. A viewer looking through the eyepiece sees a circular field divided into two equal halves by a fine line. The specimen mounted under the left-hand objective lens appears in the left half of the field, and the specimen under the right-hand objective lens appears in the right half. A comparison microscope is used to make side-by-side comparison of specimens.
- The comparison microscope enabled firearms examiners to compare a side-by-side magnified view of two bullets and thus to determine whether they were fired by the same gun. Bullets fired through the same barrel display comparable markings, called striations, caused by the rifling of the barrel. If the striations on two bullets viewed through a comparison microscope are alike, the examiner can conclude that both bullets traveled through the same barrel.
- The stereoscopic microscope presents a three-dimensional image of an object. Also, whereas the image formed by the compound microscope is inverted and reversed, the stereoscopic microscope forms a right-side-up image.
- The stereoscopic microscope is the most frequently used microscope in the crime laboratory. Its wide field of view and great depth of focus make it an ideal instrument for locating trace evidence. Its large working distance (the distance between the objective lens and the specimen) allows for the microscopic examination of big, bulky items.
- A beam of light passing through a polarizing crystal emerges vibrating in only one plane. When plane-polarized light passes through a second polarizing crystal set perpendicular to the first crystal, the light is blocked by the second crystal.
- The microspectrophotometer allows the forensic scientist to view a particle under a microscope while at the same time obtaining its absorption spectrum. This provides the forensic scientist with added information to help characterize trace quantities of evidence.
- The infrared microspectrophotometer identifies a specimen by obtaining its IR spectrum, which is unique for every chemical substance. The technique is used to analyze fibers and paints.
- A scanning electron microscope uses a stream of electrons to create an image of the specimen being studied; all other microscopes use light coming off the specimen to create an image.
- When the electron beam of the scanning electron microscope strikes a specimen, it creates X-rays that can be sorted by an X-ray analyzer. Because each element emits X-rays of characteristic energy values, the analyzer can identify the elements present in the specimen based on the energy values of the X-rays emitted by the specimen.
- Possible gunshot particles remaining on a shooter’s hands are lifted off with a piece of adhesive tape; the tape is then examined under the scanning electron microscope. The X-rays produced by the particles are analyzed and displayed according to their energies. This allows the examiner to detect the presence of elements frequently found in bullet primers.
SUGGESTED ANSWERS TO END-OF-CHAPTER ASSIGNMENTS Review Questions
- Eyepiece or ocular lens
- Vertical or reflected
- Monocular; binocular
- Magnifying power
- Numerical aperture
- Field of view
- Depth of focus
- Working distance
- Scanning electron
Application and Critical Thinking
- The stereomicroscope should be used to view the outside of the leaf surface because the leaf is an opaque subject which requires the use of vertical illumination. The transmitted light microscope should be used to view the leaf cells because they are translucent and light can be transmitted through them and to the analyst’s eye using this instrument.
- The crystals which show bright colors are polarizing crystals and those that appear dark are non-polarizing crystals. With this information it can be concluded that the white powder contains at least two different kinds of crystals and is, therefore, a mixture.
- The analyst can use an infrared microspectrophotometer to identify the fiber’s general class by its IR spectrum. The IR spectrum for the crime scene samples can then be compared to those of the clothing fibers. Also, the analyst can identify the generic class of a fiber utilizing a polarizing microscope for determining the fiber’s parallel and perpendicular refractive indices.
- They must first remove any possible gunshot particles remaining on the suspect’s hands using adhesive tape. At the crime lab, the tape can then be examined under the scanning electron microscope. The X-rays produced by any particles on the tape are analyzed and displayed according to their energies. The examiner can then detect the presence of elements frequently found in bullet primers and dispersed during the discharging of a firearm.