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Law and Morality |
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Expert Testimony - An Exercise in Authentic Assessment The Scientist in the Witness Box - Deborah Crough, Saddleback High School |
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Contents of Curriculum Unit
General Statement The Intersection of Science and the Law Students are well aware that in America the law and courts play a large role in society. Courts of law provide a mechanism for sorting through competing claims and conflicting opinions or interpretations. The courts are continually tested over legal issues, guilt or innocence, by the current revolution in science. With recent developments in DNA analysis, laser technology and advancements made possible by computers, expert testimony by a criminalist is increasing in frequency and necessity. Technological awareness and knowledge of the average citizen is no match for the explosion in scientific knowledge. Citizens who serve on juries are expected to understand complex information presented by expert witnesses. With this in mind, the role of the scientist or criminalist as an effective teacher and communicator becomes even more significant. Because both scientists and attorneys begin with hypotheses, a mock court of law will prove to be a valuable and authentic form of assessment. Science and scientists are drawn into courts of law, not as adjuncts to the legal fact finding procedure but because technological advances are continually changing and reforming. The need for a scientific lesson or thumbnail course in court must keep pace with the advancements in science. It is this that requires the scientist to take on the role of a precise practitioner with legitimate expertise. While scientists will most often agree on the results of the analysis, it is the area of interpretation that will produce differences of opinion. For example, the reconstruction of events leading up to a homicide may be based on physical evidence, but the interpretation of that evidence is not an analysis. An analysis is a series of observations, measurements and a collection of facts that are chemical or physical in nature. For example, the area of ballistics includes measurements that are direct (width of bullet, number of lands and grooves) and indirect (spectral analysis of gunshot residues). Interpretation of such data consists of taking these observations and translating them into a form that is consistent with known data and then proving a conclusion about the crime. Forensic scientists must communicate their findings to police, attorneys, reporters, judges and to the general public (juries). This requires that highly technical and complex information be translated to the appropriate level of the audience. The information must be coherent, concise and logical in presentation. The language used during testimony in court must be informative but simple.
Overview
What a court will require of a criminalist or expert witness is impartiality, relevancy, clarity, and reliability. His testimony must be based on evidence that is indisputable and backed by scientific evidence. The criminalist will first give the basic facts as he or she interprets them, then his/her opinion as to the significance of them. In this respect, expert evidence will differ from that of the usual witness, who is not normally allowed to express an opinion. The person who gives expert testimony not only is allowed to express an opinion but is expected to do so. The Courts require a forensic scientist to be credible, completely objective and above all impartial. To establish reliability for the court, the expert must make the jury feel he/she is a person of absolute integrity, and that the opinions expressed have been formed with scrupulous care. The scientist needs to be convincing when testifying that every precaution to avoid error was taken during the investigation and analysis. As seen in some very public trials of late, the scientist must avoid unnecessary technical jargon and proceed carefully to avoid giving the impression that he/she would try to blind the jury with science. The delivery of the testimony will be far more likely to have success if the scientist sticks to the main idea and avoids explanatory lecturettes. This is something K-12 educators can relate to&emdash;Keep It Simple or Less Is More. During cross-examination, defense lawyers may suggest to the scientist that there may be room for error of interpretation&emdash;and that, of course, is frequently a possibility due to the inherent nature of science. Science is based on the formulation and testing of hypotheses about the physical and biological world. So to counter such examination, the scientist is open to draw attention to length of experience as well as the number of confirmatory tests that have been made to support the testimony. Again, the focus will be on reliability and credibility. Also the scientist must admit to the possibility of another expert forming a different interpretation or opinion based on the same facts. On occasion, if the witness published or mentored in the field, some previously published statement may be used against him/her. The expert witness must not get hung out on a limb in court. Such a situation would be fatal to any specific evidence and damaging to the criminalists' reputation. The "rule" is if he/she is in doubt or simply not sure, he/she should say so. Thus, the preparation before court is critical in avoiding pitfalls. All practicing scientists are aware that no hypothesis can ever be proved in the strict sense of logic but can be disproved by the discovery of a fact that is inconsistent with the hypothesis. In the absence of such facts, the criminalists accepts the hypothesis as provisionally established according to the amount of information and the reliability of that data to demonstrate its truth. Criminalists persevere to establish that the truth of a hypothesis is proved "beyond all reasonable doubt."
Unit Statement Authentic Assessment in the Science Classroom Students will be asked to model the process of a court of law. They will practice the work of an investigator at a scene of a crime as well as a criminalist in the laboratory.
They will be required to demonstrate an understanding of the science behind the investigation as well as interpret that data in the simplest language possible. Thus, the final project of a presentation in "court" will be a testimony that exhibits clarity and demonstrates understanding. They will use data to interpret the evidence collected. By stepping into the role of criminalist, they will develop cognitive skills and higher level thinking. Students will need to use critical thinking about the role of science within the parameters of the legal process. They will become involved in the practices of a criminalist, which includes research. Context-specific information will be compiled to support a position and to provide further "evidence" based on the data. For this part of their preparation, students will utilize the library as well as the Internet. As qualified "experts," students will demonstrate to the court their knowledge and experience, as well as their opinions and interpretations of the facts of the case. They will need to formulate and revise their explanations using evidence and logic. They will be forced to self-evaluate and present scenarios based on scientific knowledge and probability. Students will be challenged to prepare testimony that will help the jury understand the physical evidence, analysis and the conclusions that can be drawn from it. The measure of success with this presentation will be based on preparation, clarity of testimony and responses to cross-examination. Overall, the success for this project will be with the students, who will be given the opportunity to debate, participate and prepare for a career in the justice system or other public sphere. The Scientist in the Witness Box will provide students the opportunity to discover, analyze and manage information, as well as develop, communicate and evaluate ideas based on scientific principles.
What This Unit Will Do Strategies for Teaching and Preparing Students Teachers of science do not need statistics or demographics to alert them to the vast array of obstacles to learning in the classroom. These are especially evident to the science teacher. Many science teachers have adopted a multidisciplinary approach in general science classes. As a result, teachers require a broad knowledge of all disciplines of science: biology, physics, chemistry, geology, botany, anatomy and physiology. Forensic Science provides the perfect vehicle for the delivery of such material. Thus, a need for a modus operandi that selects a range of classroom techniques is essential and useful. "A person who has a cat by the tail knows a whole lot more about cats than a person who has just read a book about cats." The objective of this project is to encourage educators to be creative in their approaches to produce learning. "Old methods must be replaced by more fruitful approaches that will facilitate learning of both the English language and the fields of science." Powerful teaching requires educators to create and think "outside of the box." Lessons 1-4 are laboratory applications based on inquiry methods of learning. Students will be required to identify and match found "evidence" to exemplars or standards they have prepared. Lesson 5 is assessment by demonstrating the application of new knowledge and skills. These strategies can be enhanced by the collaboration between disciplines and community resources, i.e., math, language arts and science, local laboratories and criminalists. The techniques suggested develop students' skills in speaking, listening, writing and reading. The laboratories are designed to prepare the students for the authentic assessment portion of this project, as well as the "court room" performance evaluation. Hands on activities are essential to the success of scientific literacy. Thus, the laboratory activities included will provide the foundation for the crime scene portion of research and assessment. It is the intent of this unit that students come away with a sense that 1) in a democratic society citizen involvement is a responsibility and 2) science is based on practices that are reliable and repeatable and that it is the process of this method that insures reliability.
Unit Plan
General Objectives
Behavioral Objectives
Activities
Overview: Lessons 1-4 Students will be required to maintain a laboratory journal of standards to be used for comparison with unknowns found at various crime scenes. They will prepare their own slides and maintain precise records and sketches as official documentation (real-life connection). These records are to be at a high standard that will hold up in a mock court of law. The procedures involved in these laboratories model what is done in an actual crime lab. The student journals will thus become a reference for the "criminalists" during the final preparation for court. The Laboratory Journal will be broken into four sections of trace evidence (the "guts" of criminal investigation). Students will complete a microscopy unit in advance, and it is to be understood that they will be proficient in using the microscope and recording their data with great detail and depth. This unit may be extended to include more biology or chemistry. For example, a pathology lab could be included to have students compare and contrast normal and diseased tissues of several major organs. These slides can be obtained through most large vendors of scientific equipment (i.e., Boreal, Flinn). It is recommended that if choosing organs to study, the teachers build on their own knowledge and strengths&emdash;limiting the number of organs&emdash;if background in physiology is limited. Please refer to a list of reference and resource materials that will augment these labs and complete "the big picture" for the students. Trace evidence is expected to be a major portion of any forensic curriculum. Teachers may want to add to this section of the unit, and it would be easy to do so if the curriculum and calendar permit.
Note: By no means is this representative of the scope of trace evidence. Students will be required to complete a microscopy unit and record their observations in the journals. Standard samples of hair, fibers and tools will be provided for examination. Students are expected to maintain a high level of depth and detail to their sketches and observations. The journal will become the only resource available during the lab portion of the final assessment.
Lesson 1: Physical Evidence Background
The goals in processing a crime scene include the following: Determine what is evidence; package appropriately and label to avoid errors in collecting; record pertinent information such as location; make appropriate sketches; and determine what would be an appropriate standard of comparison. Physical evidence can be defined as anything that has substance and is tangible. In determining what is evidence, the type of crime that appears to have been committed must be considered. Items that are unrelated or foreign to the scene, unusual in their location or in the number of items, damaged items, or those whose relation or position to other objects suggests a pattern that fits a crime, must be considered. Standards of comparison must always be available to give credibility to the evidence in question upon analysis. This would be a good point to reinforce the nature of science and the scientific method. A standard is any object, measure, or model with which the evidence can be compared in order to determine whether both came from the same source. Collection of evidence has a direct influence on its later value and requires judgement in care and handling. Procedures for testimony require one officer to collect the evidence and another to document. Notes will be taken on location, description, and condition of each item. Common errors in collection include the following: not enough evidence was collected, standards were not collected for comparison, and the integrity of the items was not maintained (i.e., there was cross contamination or improper packaging). Protection of the evidence is often the weakest link in maintaining the chain of evidence. Examples might include improperly sealed containers, envelopes that open, labels or tags that fall off, labels that become illegible, and deterioration or contamination. Evidence is classified based on class characteristics and individual characteristics. Class characteristics are features that place an item into a specific category (i.e., a hammer versus a pair of pliers or a screwdriver). Individual characteristics are those that distinguish one item from another of the same type. For example, one screwdriver might show a chip or considerable wear of one side. Evidence is further broken down as being referred to trace, direct, circumstantial or probative. Trace evidence is extremely small items such as hair or fibers and requires microscopic examination. Direct evidence holds direct incrimination such as blood alcohol or DNA. Circumstantial evidence is indirect incrimination such as a footprint at a crime scene. Probative evidence will be considered essential or vital to the case and will prove innocence or guilt beyond reasonable doubt. This unit will cover specific areas of trace evidence: hair, fibers, tooth marks, and tool marks Hair: Hair can be difficult to locate (so can fibers for that matter). Sufficient lighting is required. Often the crime scene will be vacuumed and the material then sent to the forensic lab. Microscopic examination of hair can determine species (is it human?), what part of the body it came from, whether it was pulled out by force, burned, and whether there is blood on it. If the root is present and intact, DNA analysis can be done. Threads and Fibers: Ropes, twines, fabric and fibers are often used in crimes, and hence, left at the scene. Laboratories have various comparison standards and can sometimes even determine the manufacturer of the item. Cordage can be compared for composition, color, diameter and how it is constructed. Rope-ends can be a direct match if they are frayed or cut. Fibers fall into four categories: mineral, vegetable, animal and man-made or synthetic. Mineral fibers include glass and asbestos. Plant fibers include jute, cotton, hemp and linen. Fibers that are animal in origin are primarily of wool type (sheep, alpaca, angora or mohair) and silk. The man made fibers include rayon, nylon, orlon and polyesters. Each fiber can be analyzed physically and chemically. Each fiber has individual characteristics that are particular to that fiber. Because of the multitude of characteristics, fibers are easier to distinguish between than hairs. Fiber examination would include visual examination to measure thickness, number of fibers per strand and tests for shape and color. Hit and run accidents often yield fibers that adhere to the car. Soil and Minerals: Soil found on shoes, clothing, carpet or tires can be identified by color, texture, particle size, density and it's biotic/abiotic composition. Identification can be determined by microscopy and by X-ray diffraction. Pollen and spores can be identified by electron microscopy. Standards for Comparison For this unit we will focus on the most commonly questioned evidence: hair, fibers and soil. We will be doing a series of activities in an attempt to identify the evidence in question. There are specific procedures for collecting the evidence and for the analysis. It is critical to solving any crime that the scientist use methods that are non-destructive whenever possible and that the evidence is conserved (minimal amounts are used in analysis). You will need to keep these points in mind when conducting your own analysis. How you handle and preserve the evidence will be considered part of your grade. These are samples from a known source. In other words, you have samples of silk to compare to your unknown or questioned evidence. Upon examination and testing, it is confirmed that the fiber in question is silk. The laboratory comparisons you will conduct will determine whether or not the questioned and the standard have a common source of origin. Examples of standards may include samples collected of different types of plants along a path traveled by the criminal; samples of undamaged auto paint that is close to the damaged area; carpet samples; bullets fired in the forensics lab from the suspected weapon; fibers from a garment that are similar to fibers found at the crime scene.
Lesson 1: Trace Evidence-Hair and Fibers
Teacher Notes Duration: 2 days
Pre-lab: Prepare students for activity one day in advance. Discuss the value of using samples as standards for the evaluation of associative evidence. *If microscopes are not available, a lot of visual examination can be done using a hand lens or a jeweler's eye loupe. Plastic loupes are reasonably priced, and one can obtain a magnification of 10X by using two (one on top of the other).
Student Background/Introduction
For the past few years, science has been making a much-celebrated comeback. Perhaps no area of scientific study has become more popular in recent years as the forensic sciences, the study and practice of applying science to solve crimes. From the Iceman to O.J., you would have to be living on the moon not to have heard some mention of forensics over the past few years. When people hear the term forensics they usually think of the criminalist, the Sherlock Holmes who analyzes physical evidence such as hair, blood or fingerprints to crack the case! But there is more to forensics than crime scene analysis. Examples of other people involved are the pathologist who performs the autopsy, the forensic entomologist who studies insects to help police with crimes and the forensic anthropologist who uses his or her knowledge of the human skeleton and cultures to solve crimes or mysteries that leave behind nothing but bones. Part Sherlock Holmes and part Indiana Jones, the criminalist can construct a life and death from the most minute piece of evidence. (Resource: The Discovery Science Center &endash; "The Lead Coffins," Santa Ana, CA) In a criminal case, proper microscopic technique during the handling of evidence is of extreme importance. The activities you will be completing in the next few days will show you proper lab technique, as well as introduce you to some new evidence found in this investigation. Upon examination of the clothing, hairs and fibers not consistent with the victim's were found. This trace evidence will be compared to the standards you are to collect in preparation for your testimony.
Lesson 1 Background Reading To work in a forensic laboratory involves a fair amount of training. The training or background required extends across many levels: from the crime scene technician to the investigator to the lawyers and finally to the courts, where the forensic scientist might finally present his/her findings. This handout will provide you with a general background of a criminal investigation, from the initial crime scene to a court of law. Physical Evidence Physical evidence is evidence that must be collected from a crime scene. It often consists of several samples of the same evidence that must be compared with one another to determine whether or not they share a common origin (did they come from the same item?). If the evidence warrants it, a conclusion can be made. In other instances, it may only be possible to state that the samples could have shared a common origin (come from the same item or place). When comparing evidence, forensic scientists will ask for certain types of samples. They will try to provide the most complete and comprehensive conclusion possible. Physical evidence is collected and grouped according to its origin. Questioned Evidence This is the evidence that is foreign to the crime scene. Materials that would not normally be present may be brought there by a perpetrator and left behind. Examples may include bullets or cartridge cases, blood or saliva stains, paint chips, grease from hands, and hair and fibers left behind on clothing or carpet. Materials that are normally present at the scene can be picked up and transferred without the perpetrator being aware. This type of questioned evidence also includes soil, bark, grasses and assorted plant fragments, paint chips, wood fragments, blood and saliva of victim, and hair and fibers. Standards for Comparison For this unit we will focus on the most common questioned evidence&emdash;hair, fibers and soil. We will be doing a series of activities in an attempt to identify the evidence in question. There are specific procedures for collecting the evidence and for the analysis. It is critical to solving any crime that the scientist use methods that are non-destructive whenever possible and that the evidence is conserved (minimal amounts are used in analysis). You will need to keep these points in mind when conducting your own analysis. How you handle and preserve the evidence will be considered part of your grade. These are samples from a known source. In other words, you have samples of silk to compare your unknown or questioned evidence to. Upon examination and testing, it is confirmed that the fiber in question is silk. The laboratory comparisons you will conduct will determine whether or not the questioned and the standard have a common source of origin. Examples of standards may include samples collected of different types of plants along a path traveled by the criminal, samples of undamaged auto paint that are close to the damaged area, carpet samples, bullets fired in the forensics lab from the suspected weapon, and fibers from a garment that are similar to fibers found at the crime scene.
Lesson 1: Trace Evidence&emdash;Is it Human? Is it Hair? Student Activity Background Hair is a slender threadlike outgrowth from the follicles of skin from mammals. A microscopic examination of the item in question can reveal if it is human or another animal. Hair presents itself as indirect or circumstantial evidence in a court of law. This evidence can be used in conjunction with other examples of physical evidence. The criminalist would testify that the two hairs are "very similar." It is statistically impossible to prove they come from the same person or source. The expert witness would never say, "In my expert opinion, these two hairs are from the same source." Instead he or she would say they are "consistent" with those of the accused. Forensic examination will focus on the hair for it's cuticular scale pattern, color&emdash;due to melanin deposits in granules&emdash;shape of medulla pattern, the root of the hair (if present) and the shape of the end of the hair (has it recently been cut?). All hairs share common elements Hair possesses a tough outer cuticular scale called the cuticle. An impression of this can be easily made with clear nail polish. Cuticle scales cover the outside of the hair shaft and point towards the tip. They vary widely in pattern and shape in mammals. They are a representative "print" to identify a species. Hairs have an outer layer called the cortex and an inner core called the medulla. The cortex may contain air spaces called cortical fusi and pigmentation. The medulla is a canal-like column of protein that runs through the core or center of the cortex. The cortex gives hair its shape. Hair that is very round will be straight. Hair that is oval will be curly or wavy, depending on the degree. Hair that is extremely oval, almost like a crescent moon pattern, will be kinky. Pigment is also laid down in the cortex. Characteristic patterns are found in the medulla and are recognized as being identifiable species markers. Microscopic Analysis A hair comparison will involve the microscopic examination of large numbers of hairs. This is done on each hair from root to tip. It is usually done in a non-destructive manner using a temporary mount. Thus, the evidence is saved in case the prosecution chooses to do its own testing and examination. The microscopic appearance of a hair will vary on the same individual. Ideally, a sample of 20-40 hairs will be used in the analysis. A sample as large as 200 hairs will often be used in the analysis. The tip of a hair can be similar to the middle region of a hair from a different person. For this reason, hairs are compared side by side at equivalent distances from the root (i.e. 1cm from the root, 2cm from the root). Hair fragments and incomplete hairs are not suitable for this type of study. Without an end/root there is no starting point for comparison. Although a hair comparison can never lead to identification beyond reasonable doubt, there are some conclusions to be made from this type of analysis. The hair in question is similar to the evidence sample and could possibly be the same individual. The hair in question is not similar to the evidence sample. It could not have come from the same individual. Lastly, the comparison has lead to inconclusive results because of the lack of deviation, lack of root, or insufficient sample. Remember! Protection of Evidence is Critical!!
Procedure: Using forceps, remove a hair sample from each fur source provided by your teacher. If the hair is attached to a skin, be sure to start at the root end in your examination. The Cuticle Cast
The Temporary Mount Lay a hair across a clean slide and add 3 drops of mounting medium. Add a cover slip and sketch the hair. Pay close attention to the pigmentation and patterning of the cortex and medulla. These offer clues as to the identity of a mammal. Optional: Make a cross section of each sample as time permits. Refer ahead to Lesson 2: Fibers. This lesson includes details on how to make a cross section. Use the cross section to examine various types of human hairs.
Lesson 2: Trace Evidence&emdash;Fiber Science Teacher Notes
Students will need to prepare a set of standards in their journals. Many popular crime novels include fibers as a form of evidence for a crime. Reading a passage that demonstrates the power of this type of evidence serves as an excellent elicitation exercise. Patricia Cornwall's Body of Evidence has several passages that demonstrate the importance of trace evidence. The fibers that are selected by the teacher should include natural and manmade-synthetic fibers. One can choose to use thread or fabric swatches for materials. The teacher will need to demonstrate how to pull a thread apart to obtain a fiber. Emphasize that the students need to understand the depth, detail and scale of their sketches and that this is of importance to their investigation. These sketches will be documented in a laboratory journal. A set of natural fibers should include cotton, linen, silk and wool. Synthetics include polyesters, rayon, orlon and others. Some of the older fabrics can be difficult to locate; however, thrift shops are an excellent source, as many of the older garments are made from these "dated" fabrics. A temporary mounting medium can be made from glycerol and ethanol in a 50-50 percent solution. Students should mount the longitudinal sections with the medium and a glass cover slip. Cross sections can be made by sealing fiber in polyethylene plastic of a heavy weight. Using freezer baggies works, as the plastic is of a thicker weight than sandwich bags. Remember to use clear plastic when melting the plastic&emdash;use either black binder clips or large paper clips to hold the slides in place. Clear nail polish should be used in teeny-tiny amounts to hold the plastic section in place on the slide for observation. I have students take the end of a flat toothpick and use it as a "microspatula" for depositing the nail polish on the slide. When making cross sections, this will take PRACTICE by the students. This procedure can be eliminated if time does not allow for the development of these microtechnique skills. When discussing polarization of the light from the fibers, be sure to cover the physics involved, the nature of the film, and the value of the information it provides. Students will polarize their microscopes by placing a small piece of film on top of the light source, and the second piece will be used to cross the polars. The students will rotate this piece slowly 380 degrees and record the colors they see. Remind them that this information serves as an identifying marker or a print of a particular material. Note: For lesson 1, a greater variety of hairs (in laboratory one) can be collected by looking for old fur coats or by requesting samples from your veterinarian or zookeeper.
Lesson 2: Trace Evidence, The Power of a Fiber Student Activity REMEMBER&emdash;PROTECTION of evidence is critical! This lab includes destructive lab applications as well as non-destructive. Be sure to be conservative with the evidence. You will damage small samples when you make cross sections of the fibers. SAFETY PRECAUTION: You will be using hot plates and single edged razor blades. Please be careful and use caution. The slides and the metal "holders" will get HOT. The razor blades will be used in close proximity to your fingertip.
The Longitudinal Section Temporary Mounts Be sure to start with a clean slide and glass cover slip. Place a fiber on a clean slide. Make sure you have a single fiber. Place 3-4 drops of mounting medium on the fiber and a cover slip on top. Examine under low and high magnification. Sketch the standards in a 10cm by 10cm box (for each fiber) in your laboratory journal. Pay close attention to the margin, morphology, shape and minute details. The sketches you make today will be your reference for the evidence examined for the case. You will need to classify as natural or synthetic fiber.
The Cross Section You will need to make a sandwich of a clean slide, a small piece of plastic (enough to cover fiber only), fiber, another piece of plastic of the same size as the first, and another clean slide. Once this is done, bind the sandwich together with clips provided by your teacher. Heat the slides gently in a flame or on a hot plate. Remember to gently heat this&emdash;not too hot or too fast. Look and monitor to see if the plastic is melting. Do not burn the plastic. Once it has melted, allow the slides to cool. Using a probe or toothpick, pry the sandwich apart and remove the plastic. It should have the fiber encased inside. Lay the fiber flat across something you can cut on, like a sandwich board. Using your thumbnail as a guide, make tiny slices across the plastic and cut the fiber into sections. Remove the smallest section for mounting. Turn the plastic on its side. You are now looking down at the fiber from its end. Glue the section firmly into place using nail polish as demonstrated by your teacher. Add two or three drops of mounting medium. Examine and sketch as you did for the longitudinal sections. Do this for each standard fiber provided. Clean using acetone, or scrape the slide clean with a razor blade.
Background The forensic odontologist will examine and classify the teeth of unidentified people when other forms of identification are not available. He/she can also analyze tooth patterns or bites and look for similarities. Bites are often left behind on food items such as gum or fruit. When bite marks are found, they can be cast in the same way as shoe or tire impressions are made. In this activity you will obtain bite marks, compare them to the evidence, and attempt to reveal the identity of the perpetrator. A crime has been committed. A rash of pencil thefts has occurred in your classroom. The last #2 pencil in the room has been stolen. Your instructor cannot complete the scantron sheets necessary for attendance and grades. You are to compare the bite marks of individuals known to have a compulsion for wood pencils, and who have entered the classroom in the last hour. The Deputy Sheriff (your teacher) who was first on the scene has collected the evidence. The pencil in question was found in a trashcan. The pencil has been altered since it was last seen. Standards are to be collected and compared from individuals in question.
Procedure Using materials and evidence available, you are to collect casts of bite marks and document your findings in great detail. If bite mark is not deep enough, it can also be traced onto transparent plastic taped over the impression. You are also required to make measurements of individual bite characteristics and make written notations in addition to your sketches. Remember that sketches must demonstrate great detail. Measurements of bites are to be made in metrics. Missing teeth, teeth that do not meet or line up, bridges or other unusual dental work must be noted in your written description. Be sure to form some conclusions about the validity of your work in solving this crime. If you have a suspect, you should continue your collection of impressions to show replication and validate your findings in court.
Using a set of pencils, ask students or fellow teachers to gnaw on them and leave fairly deep chew marks. For collection of standards for comparison, you may use a number of soft impressionable materials. I have used a variety of materials to make "casts" and recommend you use at least 3 different materials. The following list will work equally well&emdash;but some materials cost more than others and most are consumables. Crisp apples, chunks of cheese, chocolate bars, and soft white bread work well. (Inform students that real burglars often raid refrigerators and snack. They often are sloppy crooks and fail to clean up after themselves&endash;great physical evidence). Try thin sheets of balsa wood or Styrofoam plates cut into "bite" size pieces. Students will get full uppers and lower impressions from this material. Remind them to label by name and top or lower bite. Use plastic wrap to cover the material before they collect a bite. This is disposed of afterwards and cuts down on spread of microbes from the oral cavity. Thin sticks of balsa wood provide a great model for the pencil in question. Flattened pieces of clay wrapped in plastic make for excellent casts, and the clay is reusable. You may take this opportunity to point out that the saliva left behind can be tested for protein markers, or any cells from the mouth can be used in DNA printing. The pencil in question is evidence. You select the perpetrator. Have fun "fingering" your colleagues. This lab will work as long as students collect standards from a list of known suspects. Using students from within the period will work, or you can extend this out into the campus community.
Protection of Evidence is Critical! Background The criminalist will examine the pattern of marks left behind at the crime scene and attempt to connect any evidence found to those marks. All tools show individual identifiable characteristic marks. These marks are left behind as part of the manufacturing process or from the use of the tool. These marks can be considered the particular "print" of the tool in question. If ownership of a tool can be confirmed and the marks or "scars" match, the forensic team has found their perpetrator. The last of the evidence is to be collected. There is obvious evidence of a forcible break in. Your assignment is to record impressions and seek justice.
Procedure
Small sections of heavy-duty aluminum foil or brass shin-stock should be used. The advantages of aluminum foil over another metal are that it makes great impressions and is most malleable. It has the best resolution as a result. Drawbacks are that it is so soft it does not maintain it's integrity easily and records unwanted marks and crinkles. The heavier brass foil holds impressions better. There is less resolution but handling of this material is also less likely to destroy or damage standards. Ask students to bring in tools. Number them or use identifying labels. Select several tools to use in your crime scene. Take small boards of pine or balsa wood and make impressions as if someone were trying to commit a break-in. Tape these marks next to an entrance (i.e. by a doorhandle or lock). Set up a scenario of your own creation. "Someone knew I had a stash of chocolate bars." Involve your colleagues or timely situations at your school in your fictional story. Ask students to collect their "standards for comparison." Have them keep them labeled by writing the identifying tool next to the impression. For example, "tool A" and then the screwdriver's impressions from various angles. A pre-lab discussion and demonstration will assist in the success of this activity.
Remember&endash;Protection of Evidence is Critical in Forensics Checklist for Physical Evidence
Evidence can be picked up and transferred without the perpetrator being aware. This type of questioned evidence also includes soil, bark, grasses and assorted plant fragments, paint chips, wood fragments, blood and saliva of victim, and hair and fibers.
Student Background In this final activity, you are required to complete preparatory steps for litigation to prepare your testimony for court. Your teacher has prepared a script of characters and participants for you. Your job is to take the evidence you have collected&emdash;your records, data and analysis of this evidence and prepare some written notes for a court of law. A jury will be present. You will have to prepare some educational notes for them. All of this preparation will require written research and documentation to support your conclusions and findings. Be prepared for some tough cross-examination. Lawyers are not known for gentle tactics. Your teacher may have invited some outside guests to be present for the evaluation of this debate.
Background New Jersey's Supreme Court has a written definition of "reasonable doubt" and mandates that all judges in criminal trial consistently use this precise wording when delivering jury instructions: Proof beyond reasonable doubt is proof, for example, that leaves you firmly convinced of the defendant's guilt and if…you are not firmly convinced of the defendant's guilt, you must give the defendant the benefit of the doubt and find him not guilty. You may be familiar with Johnny Cochran's "if it doesn't fit, you must acquit" statement during the O.J. Simpson trial. You are to keep this in mind at all times when testifying. Your professional job is to provide expert testimony that is based on scientific evidence. This is evidence that is reliable and repeatable. Additional points to keep in mind. In America, you are considered innocent until proven guilty by a court of law. Keep in mind that this means one is presumed innocent until there is proof of guilt and a jury decides that guilt lies with the accused. What roles do the media and law enforcement play in this? The media often portray and display guilt of a person who is accused of a crime. The weight of defense often lies in the power of the physical evidence to connect someone to a crime scene. Arrest and the physical detention before trial also re-enforces this. The question remains: Are we all truly considered innocent until proof "beyond reasonable doubt" exists? You are to prepare written briefs for presentation and to develop a plan for testimony. This plan is to show reflection of the science and the facts about the evidence in question. It should reflect that the expert has prepared him/herself before court by research and review. Ultimately, each of you must form an opinion based on the science regarding who is responsible for the crime. This opinion is to be made in a written narrative that is to be submitted prior to the trial. These narratives are to be made available to any outside assistance, prosecutors or guests that will be involved. Remember that different people can reach very different conclusions. But in forensics, the evidence remains the same: The conclusions based on the facts should be consistent. This lesson has been designed to show you that there are additional considerations in a criminal court that come from social, political, moral and legal perspectives.
Preparing for Court You should reexamine the evidence provided. Debrief with other members of your investigative team. Remember that an expert witness must demonstrate competence in an area of expertise (i.e., hair or fibers). They must also possess experience in litigation in a criminal court. Lastly, they must be able to answer questions for the plaintiff and or the defense in a straightforward, nonbiased manner.
The courtroom performance is designed to provide an opportunity for students to improve speaking skills through peer interaction. The purpose of this culminating activity is to encourage students to use deductive skills and reasoning based on observable or measurable facts. They are to use the science they have learned to think through real world problems similar to those they will be called upon to consider as members of a jury. Encourage students to rise to this challenge and to experience the criminal court process firsthand. TO DO IS TO UNDERSTAND. This activity will help students integrate and apply the science knowledge they have acquired.
Introduction to Lesson Defining the legal term "reasonable doubt" sometimes presents difficulties in that it is not necessarily a quantifiable concept. In such cases, the criminalist will support a hypothesis by probability calculations. Questions should be formed by presenting students with prompts for initiating inquiry: What does "reasonable doubt" mean? How does one calculate the probability that someone is guilty? How significant is the evidence in question? Can one assign a statistical "weight" to a piece of evidence? Allow for 3-4 class periods for preparation and 2 full class periods to conduct the trial. Set up an agenda to guide the students. For example:
The class is to be divided up into groups of four to five students. Design the groups so there is a good balance of science and language competence. Also, consider the students' personality differences when creating the mix. A tool that has proved most useful is to ask students to identify one person they most want to work with as well as one person they DO NOT want to work with. The teacher can always guarantee the latter, and this decreases negative tensions in a group. This becomes a form of insurance for success. Another "tool" is to include an element of peer pressure. When working on group projects that rely heavily on students staying on task, it is suggested that some grade value be at stake. By informing students that they are not allowed to spy, infringe or collaborate with opposing forensic labs or lawyers (students not in their group), one can control the amount of idle time wasted. I frequently assign a 1-2% penalty for infractions of this nature, thus relying on peer pressure to take care of "negative" work. Students are to prepare written briefs for presentation and to develop a plan for testimony. This plan is to show reflection of the science, i.e., the facts about the evidence in question. It should reflect that the expert has prepared him/herself before court by research and review. Ultimately, each student must form an opinion based on the science regarding who is responsible for the crime. This opinion is to be made in a written narrative that is to be submitted prior to the trial. These narratives are to be made available to any outside assistance, prosecutors or guests that will be involved. The instructor is to remind students to draw on their everyday experience and make real-life connections whenever possible. It is suggested that a partnership with a police officer or criminalist be established, as this is an extremely valuable classroom tool. I have two resource scientists who have volunteered to direct the preparation activities before trial. They are also playing "devil's advocate" and are on the side of the prosecution. A rubric for evaluation must be developed in advance of this activity. Students should be aware of the areas of debate on which they will be evaluated. Outside partnerships add an invaluable dimension to the classroom experience and, in situations where there are budget concerns, a viable option to the field trip experience. Provide the students with articles or texts in the areas of forensic evidence and analysis as well as litigation. Utilize the school library, or seek assistance from a forensic web site. The Internet is an ever changing source of information for you and your students. Encourage students to bring in appropriate props to increase the authenticity of your court of law. (You are the presiding Judge.) Remind them that as professionals they must dress for public testimony. Showing up in a T-shirt and a pair of shorts will NOT add to their credibility as an expert in the field of forensic science. Tables and chairs need to be arranged to model a courtroom. If a theatre or forum is available to you, that is even better. A podium, microphone, gavel, robes, court reporter and deputies will add to the ambiance of your court. This activity has intentionally been written to be open-ended. This unit is to serve as a resource and a guide for your own crime/caper. There should never be a single right answer or plot for a case. It is the analysis and the interpretation of factual evidence that is of importance. Look for the quality of interpretation&emdash;not the number of right answers. Ask students to examine the evidence and support their hypothesis and findings with science. After completion of the trial, conduct a debriefing session with the class. Students have abandoned their assigned roles and should now critically analyze the trial. Guide students so they focus on the following:
It is recommended that the evaluation be based on written and oral performance.
Glossary/Assessment Terminology
Alternative Assessment: Not multiple-choice, true/false, paper and pencil or scantron formatted. Requires students to demonstrate learning in a performance or task. Authentic Assessment: Assessment that uses real world experiences and is aligned with the standards used by the district and/or state. Students are to demonstrate skills that are aligned with these standards and framework that is in place. Benchmarks: Specific examples of student achievement. Curriculum Imbedded Assessment: The assessment is part of ongoing instruction. The courtroom drama is an example of such an assessment. Equity: That all groups are represented and allowed to perform to their full potential. Assessment should use content from a variety of sources and be representative of different perspectives and background. Peer Evaluation: Peers grade student work based on an established criteria. Rubric: Criteria that have been established in advance for scoring or rating performance. Rubrics that are valid and sound minimize biases that may be inherent in scoring. Summative Assessment: Assessments given at the end of a unit to generate grades. Grades are representative of summative data. Validity: An assessment may be reliable but not valid. The assessment selected does or measures what it states in the original objectives.
Teacher Bibliography
Teacher Resources
National Science Teachers Association, 1742 Connecticut Avenue, N.W., Washington DC 20009: (202) 328-5800. Publications include the educational journals Science and Children and the Science Teacher.
Student Bibliography
The following Web Sites may be found to be of great value.
Other Resources
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