Introduction / Background

This case study was originally developed by a forensic anthropologist and archaeologist to be used in undergraduate courses at all levels. We have used it in a 100-level introductory archaeology course, 300-level archaeological lab methods class, 400-level zooarchaeology and archaeobotany class, and an introductory level forensic anthropology course.

We developed this case in part because our students find case studies more engaging and more effective tools for learning. Assessment data collected in lower- and upper-division archaeology courses at the University of North Dakota confirm this quantitatively. Students ranked this particular case study higher in terms of their learning and enjoyment than more passive teaching techniques (see Scharf 2006). When directly assessed by the instructor, student mastery of the material was highly correlated with students’ self-assessments of their learning (Pearson’s r = 0.504 and p < 0.001), and students correctly noted that the use of case studies contributed to their learning (Scharf 2006).

Although this case was constructed with archaeology and forensic science students in mind, it was first tested with students from a wide variety of majors. The case was well received by this diverse group of students, who found it case appealing and interesting. Based on this, we believe that the case could easily be adapted for use in a variety of introductory courses, with different instructors emphasizing different aspects of the case, such as quantification, osteology, ethics, laboratory methods, or field methods.

Objectives

By completing this case study, students should be able to:

• Define and use the following concepts/tools used in archaeology, paleontology, and forensic anthropology when counting bones from a site:
  • NISP (number of identified specimens)
  • MNI (minimum number of individuals)
• Recognize a typical ethical conflict confronted by forensic anthropologists.
• Describe appropriate ethical and professional behavior for forensic anthropologists.
• Explain the effects of available information on MNI quantification.

Classroom Management

We have used this case successfully in classes ranging in size from 10 to 75 students. The case is intended to be taught in an interrupted format using a series of four interrelated stages, or parts. Each of the four parts requires 20 to 30 minutes, and can be done within a two-hour block of time (or less if time is carefully managed and monitored). As students proceed, they become more interested, more efficient, and need less direction in answering questions and initiating small group discussions. If class time is limited to a single 50-minute session, the case is best broken between Parts II and III.

Part I – A Walk in the Park

We chose a scenario in which a hiker finds a bone scatter in a nearby state park, which we present to students with a PowerPoint slide showing a photo of the setting (Lake Itasca) at Itasca State Park. Instructors may wish to adapt this to a nearby location to increase interest and relevance to their students.

After verbally presenting the scenario to the students in about three minutes, we put the following questions up on the screen and ask students, working independently of one another, to spend about five minutes writing answers in their notebook to the following questions:

• What questions do you want to answer at this scene?
• What data will you collect and how?
• What equipment will you pack in the vehicle?

After five minutes are up, we put the students into groups of five. We do this based on spatial proximity, but assigned groups would work just as well. We have found that groups of five are optimal; groups of less than three or more than six tend to interfere with student learning and allow students to stray off task. We ask the students to compare their answers with one another. To help them focus on the task, we project the following on the screen:

• Did you get the same answers as other group members? Why or why not?
• What questions do you want to answer at this scene?
• What data will you collect and how?
• What equipment will you pack in the vehicle?

At this point, we circulate around the room from group to group, listening to the answers that students have given, joining briefly in conversations, giving feedback, and keeping tabs on whether groups have finished their discussions. Usually, students need about 10 minutes for this small group interaction. When it seems that groups are finished reviewing and comparing individual responses, we go to the front of the room, call the students to attention, and go over each of the questions in turn, asking for volunteers to provide answers. This process, with commentary and discussion of Part I, should take 15 minutes at the maximum. Altogether, Part I should take about 25 to 30 minutes to complete.

Part II – A First Assessment

For Part II, we verbally describe the inventory process and the situation—there is only a half-hour of daylight remaining and the initial inventory must be completed quickly. We show students a slide depicting examples of each bone, which they are told have been identified as clearly human. The slide lists the following skeletal elements:

• 3 skulls
• 6 femora
• 4 os coxae
• 2 humeri
• 2 tibiae
• 5 scapulae

We leave this slide up for students to look at during Part II so that they can answer the questions in this part of the case. This is a good time to optionally distribute a handout to students showing them the location of these bones in the human skeleton, such as the provided handout entitled “Human Skeletal Elements” (MS Word doc format). We ask students to take a minute or two to individually jot down answers to the following questions, which we distribute to each group on a small sheet of paper:

• How could you determine if these bones were human?
• How many bones are in the collection? (This is the NISP or Number of Identified Specimens)

Instructors may wish to modify this step by including images of these individual elements, putting them on the screen or in a handout. Excellent sources of additional illustrations include Bass (2005) and White and Folkens (2005). Others may wish to modify the case study by using skeletal material (real or plastic) that students must identify to create the list. Although the use of skeletal material tends to increase student engagement, it is challenging for those who do not have prior experience with bone identification. This portion of the case could be modified for more advanced students with previous knowledge of skeletal anatomy by using fragmentary skeletal elements or a mixture of juvenile/adult or human/nonhuman remains. Advanced students could then employ vocabulary such as antimere (basically, the right or left half of the body) as well as anatomical directions (proximal, distal) in their determination of MNI. Part II sets a time limit on the inventory process (the sun will set), so the instructor should take this into account when increasing the challenge of the MNI determination.

Again, we wait until students have finished writing, then give each group a new slip to use to quickly write down the answers to the additional questions (we do this while the slide with the initial inventory is still up):

• What is the maximum number of individuals who could be represented by these bones?
• What is the MNI (the Minimum Number of Individuals—the lowest number of individuals needed to account for the bones present)?
• Why is MNI important?

When students have finished, we ask them to again compare and contrast their answers in their small groups and determine if they got the same answers and why (or why not). We allow groups to discuss for about five minutes, then bring them back together for a whole-group discussion with directed questions from the instructor that lasts about 10 minutes. Altogether, Part II takes about 25 to 30 minutes to complete.

Part III – What Do You Tell the Media?

In Part III, we give students an added complication—pressure from the media and the family of the potential murder victims. We start by telling students that they are now approached by a local newspaper reporter (we give him a name and association). The reporter wants an interview and the parents of three boys (who went missing) want information to have closure and hold a memorial service. Given this pressure, we give our teams of students a slip of paper with the following questions:

• What do you do about the newspaper reporter?
• What do you do about the family?

We tell them to jot down answers individually, and then share them with their group. We circulate around the groups and bring them back together for a discussion of approaches, potential outcomes from prematurely releasing information, and whether all information should be controlled by the sheriff.

Part III usually requires a total of 20 to 25 minutes to complete.

If students do not see any potential conflicts or problems with disclosing information to the family and media, we ask the following leading questions to get students to think about the issues more deeply. The questions (below) are optional and are meant to be introduced in the class discussion to help the students consider both sides of the premature disclosure problem. Instructors not wishing to use them can go directly to Part IV.

• If you were the family with missing children, how soon would you want information about these remains—immediately at the scene, or days/weeks later after the analysis?
• If you gave one answer and the sheriff gave another answer, what will the public think about your investigation?
• If you talk to the public, what will the sheriff think about this action?
• Should information about the scene be controlled, and if so by whom?

Part IV – The Final Inventory

For this last part of the case, we tell the whole class that it is now the next day. There is more time to study each bone in greater detail and additional information can be added to the inventory. We put up a slide listing the following updated inventory of skeletal elements:

• 3 skulls
• 6 femora (4 right and 2 left)
• 4 os coxae (1 right and 3 left)
• 2 humeri (right)
• 2 tibiae (left)
• 5 scapulae (3 right and 2 left)

Again, we leave this slide up for students to look at during Part IV so that they can answer the rest of the questions we pose to them. We ask students to take a few minutes to individually jot down answers to the following questions, which we give to each group on a slip of paper:

• Based on the revised inventory, would you change your NISP? Why or why not?
• Based on the revised inventory, would you change your MNI? If so, what would be the new MNI?
• What do you tell the sheriff?
• Why is this important?

We tell students to compare their answer with other students in their small groups. (At this point, they know the procedure and pass into group work fairly automatically.) We circulate around the room listening to student discussions. As groups grow quiet, we return to the front and have students volunteer answers to the questions. We make a point of discussing how information levels can change MNI, and how that impacts an investigation, focusing on how the collection does not change but how our observations and interpretations can change. In addition, we discuss different ways of phrasing reports and press releases, the timing for releasing information, and how to be conservative yet accurate and responsible in dealing with law enforcement, the press, and the public. We finish with a consideration of ethics. This discussion typically lasts 10 to 15 minutes; as part of this, we entertain questions from the students on these or related issues. Altogether, Part IV takes about 25 to 30 minutes to complete.

Blocks of Analysis

This case study uses a potential homicide investigation to engage students to think about quantification, research questions, and ethical issues. Quantification of bones in an assemblage is a procedure conducted in many fields including forensic anthropology, paleoanthropology, paleontology, bioarchaeology, and zooarchaeology. The processes of a criminal investigation are identical to those of a scientific investigation—initial observations lead to hypothesis building, testing, forming of conclusions, and reporting of results. In addition, the case provides students with a framework within which to consider ethical concerns (decisions of right and wrong) as well as how the decisions made while recording and presenting information influence data interpretations and other actions derived from obtaining data. In this way, students can practice skills basic to science, specifically the development of research questions and quantification.

Research Questions

Our case begins by asking students what questions they would ask about the bone scatter that a hiker has found at a state park. This is a critical first step, as it determines what methods will be used (what tests will be applied), what equipment will be taken (what materials/resources will be needed), and what observations will be made (which variables are recognized for investigation). This in turn leads to how behavior affects process since certain tests and tools appropriate to this scenario derive from consideration of standard practices, safety and security, and issues relating to confidentiality. (A potential murder scene, for example, must be handled differently from a scatter of deer bones.)

Taxonomic and Skeletal Element Determinations

One of the earliest steps in looking at bone assemblages is to create an inventory. Bones are sorted into identifiable taxonomic categories. Are the bones bird, mammal, or fish? If they are mammal, are they human? Domestic dog? Deer? Such determinations can be made by comparing bones in the recovered sample with bones of known origin in terms of their shape, size, and landmarks. Bone atlases, researcher expertise, and comparative specimens are used for making such determinations. Useful identification manuals for human and other mammal bones include Gilbert (1990), Bass (2005), Brothwell (1982), White (2000), and White and Folkens (2005) (see (References below). For students who are not familiar with skeletal nomenclature, we have developed a simplified guide with many of the anatomical names for human skeletal elements labeled on it (see handout entitled “Human Skeletal Elements” in MS Word doc format). This handout can be used as a resource for students working on this case study.

NISP Determinations

One of the first steps in bone quantification is to count the number of bones that can be assigned to a given species or other biological taxon. NISP, the number of identified specimens in a bone collection, is a fundamental concept and starting point in bone quantification (see Chapter 6, pp. 54–67, in O’Connor 2000 for an overview of NISP and MNI). NISP is a fairly straightforward count of identifiable bones. This count does not vary from researcher to researcher, and does not change when new information (such as age, sex, and other information) is added to the analysis. NISP can increase if conditions cause bones to break into more than one identifiable piece, or can decrease if bones decay to the point where they no longer exist or no longer can be identified. These changes usually happen before an analysis, not during an analysis, so NISP values rarely change after bones are found.

MNI Determinations

Although NISP is simple and quick to compile, it brings limited data to an investigation. Estimates of minimum numbers of individuals (MNI) are used as an alternative method of quantifying bone collections, although MNI requires more knowledge and interpretation than NISP. MNI is calculated by sorting the assemblage using an algorithm with one or more steps. For example, a very simple MNI algorithm is to assign bones that are identical by name and side to different individuals (i.e., two left femora = two individuals). The determination of MNI can become quite complex as more variables are added to create the definition of an individual. MNI criteria may include the side of a bone (right or left), the age category (infant, juvenile, or adult), the sex, the depositional unit of origin, and other pieces of pertinent information.

MNI is a useful tool for comparing assemblages. For example, assemblage “A” could have an NISP of 100 bison bones, while assemblage “B” has an NISP of 48 bison bones. A simple comparison of NISPs from assemblages “A” and “B” could lead one to mistakenly think that “A” represents a larger population of bison. But this is not necessarily the case. If all the bison bones in “A” came from the same individual and each bone in “B” was from a unique individual, then “B” would represent 48 times more bison than “A.” If we were wondering if we had an isolated bison death or a problematic condition that was wiping out small herds of bison, NISP would be a misleading research tool.

Besides MNI, bone weights, live “meat” weights, minimum animal units (MAU), bone utility indexes, and other methods are used to quantify bone assemblages, and these are selected based on their fit with the research questions being pursued. Good explanations and examples of NISP and MNI are given in Davis (1989), O’Connor (2000), Rackham (1994), and Reitz and Wing (1999). Discussions of complicating factors and statistical analyses are dealt with in greater detail in Grayson (1984).

Professional Behavior And Ethical Considerations

By setting this case in a forensic context, students are immediately exposed to considerations of right conduct versus “wrong,” or incorrect, conduct. This setting promotes discussion of ethical conduct as a scientist, and as a scientist acting on behalf of society in service to law enforcement. Students may have conflicting prior knowledge of correct behavior at a crime scene, which will make interesting points of discussion.

There are many textbooks that describe the steps for conducting a criminal investigation (e.g., (Geberth 2006, Saferstein 2007, and Sullivan 2007). All scene investigators, whether law enforcement or death investigators like medical examiners/coroners and forensic anthropologists, have the task of reconstructing what occurred at a scene based on the evidence that still remains. These investigators are reconstructing the narrative about the decedent’s arrival, demise, and discovery at the scene. Unless the death event is witnessed, the investigators have to determine what occurred after the fact. This process is aided by being able to control what occurs at the scene once it is discovered. Security procedures allow the investigator to limit who enters the scene so items of interest cannot be added or removed without documentation of the event. Good security improves the chance that the details of the narrative are accurate, without harmful deletions and erroneous additions.

Confidentiality is important at the scene because the legal categorization of the death may not be obvious and/or the details of the death, such as cause, may not be fit for public consumption. Death events are categorized into five manners. The manners of death are suicide, homicide, natural, accidental, and unknown. In contrast, cause of death is a description of the physiological circumstances resulting in death, frequent examples being cardiac or pulmonary arrest (due to something else, such as exsanguination). Since both manner and cause are determined after investigation, the interests of the State (as the representative of the general public) are protected by withholding information. The State needs to restrict access to information about the scene in order to protect its ability to investigate the death. A hanging may appear to be suicide, but when the investigation reveals it is a homicide, the State can use private details of the case to connect the suspected murderer to the death. In another example, one of the authors of this case study (Stubblefield) was once involved in a case where the suspect was held for questioning about a homicide that an informant had reported. The suspect was released because the informant was thought to be lying, and law enforcement let the weekend pass before searching the site where the body had allegedly been dumped. When our team arrived at the scene, it was obvious that there had been a skeletonized body there, but we were only able to recover a few isolated bones and hair. The site where the body had lain, marked by staining and an odor of decomposition, was conspicuously empty. The suspect had had plenty of time to recover most of the remains, having been alerted to the investigation by the questioning.

By restricting the release of information about a death, investigators may protect the privacy of the decedent’s family. It is also easier for the investigators to reconstruct the narrative from the available data as they analyze and/or interpret it without having feedback from unsolicited sources. Explicit details about the death do not need to be released to the general public since such release may cause extreme discomfort to the decedent’s family or lead to hasty speculation in the public forum.

Chain of Command

This investigation began with a hiker leading the sheriff to a scatter of skeletal material. In a criminal investigation, the applicable law enforcement agency (which agency this is will depend directly on the policies of individual states) will have possession of the scene. In many states, if a death is involved, then the medical examiner or coroner will supersede the authority of law enforcement for control of the scene until the body can be removed. A typical process in a death scene is:

1. Law enforcement secures the scene and calls in the medical examiner/coroner.

2. The medical examiner/coroner examines and removes the body and calls in specialists as needed to assist in determination of cause of death.

The law enforcement agency may simultaneously contact the medical examiner/coroner and other specialists, as happened in this case; the expertise of a forensic anthropologist was required for identification and analysis of skeletal remains. Again, the procedure will depend on the protocols established in that state or municipality. Once the body has been removed, the law enforcement agency continues to process the scene.

Scene Procedure

Typical procedure from this point includes:

1. An interview or statement is taken from the discoverer (the hiker).

2. There is an initial survey of the scene and verification that the bone scatter exists and is of forensic interest.

   1. This survey results in locating boundaries and points of entrance and exit from the scene, such that Step 3 occurs simultaneously.

   2. Whether the scene is of “forensic interest” might not be determined until well after the search and recovery process is completed. In situations like this scenario, if the bones look even remotely human to the untrained eye, then the remains will have forensic interest, at least initially. In other scenarios, nonhuman bones could be of forensic interest if, for example, poachers or vandals were suspected in the area.

3. The scene is secured by blocking entrances, exits, or the entire perimeter in an outdoor scene with evidence tape, official vehicles, and officers stationed at the control points.

   1. The perimeter has to be sufficiently secure to keep spectators, reporters, souvenir hunters, and others out. It also must be large enough to keep reporters and curiosity seekers from taking images of the evidence or overhearing confidential information.

4. Evidence items (skeletal remains and associated items) are located and flagged.

5. Specialists are contacted to deal with types of evidence that require advanced training that law enforcement officials do not possess.

   1. The coroner/medical examiner is contacted if there is a body.

   2. A forensic anthropologist is contacted, as well, if there is skeletal material.

6. Evidence items are collected.

   1. Law enforcement personnel may choose to collect personal effects not directly associated with the skeletal material (for example, a wallet on the ground may be collected, but the clothes with skeletal material still inside them will be left for the anthropologist). Collecting material ahead of the anthropologist may make it difficult or impossible to reconstruct what occurred at the scene, although a single item can be replaced with a flag or marker. Skeletal material should be collected by the coroner/medical examiner and/or forensic anthropologist.

Forensic Anthropologist’s Procedure

Although circumstances will vary for each scene, the forensic anthropologist follows a protocol for recovery and analysis of skeletal remains. For scatter scenes such as the one described in this case study, the procedure begins with a search before progressing through the steps leading to the final laboratory analysis. These steps are described below.

Answer Key

Answers to the questions posed in the case study are provided in a separate answer key to the case. Those answers are password-protected. To access the answers for this case, go to the key. You will be prompted for a username and password. If you have not yet registered with us, you can see whether you are eligible for an account by reviewing our password policy and then apply online or write to answerkey@sciencecases.org.

References

A great overview of MNI and NISP for all mammals is found in chapter six (pp. 54–67) of O’Connor (2000), listed below.

Overviews of Zooarchaeology

• Davis, A. 1989. The Archaeology of Animals. New Haven, CT: Yale University Press.
• O’Connor, T. 2000. The Archaeology of Animal Bones. College Station, TX: Texas A & M Press. (Also available in a 2004 edition from Sutton Publishing Ltd.)
• Rackham, D.J. 1994. Animal Bones. Berkeley, CA: University of California Press.
• Reitz, E., and E. Wing. 1999. Zooarchaeology. Cambridge: Cambridge University Press.

Advanced Treatment of Statistics and Quantification Issues

• Grayson, D.K. 1984. Quantitative Zooarchaeology: Topics in the Analysis of Archaeological Faunas. London: Academic Press.

Information on Identifying Human Remains and the Biological Profile

• Bass, W.M. 2005. Human Osteology: A Laboratory and Field Manual. Columbia, MO: Missouri Archaeological Society. (There are many editions available.)
• Burns, K.R. 2007. Forensic Anthropology Training Manual. Upper Saddle River, NJ: Pearson Prentice Hall.
• Byers, S.N. 2008. Introduction to Forensic Anthropology. Boston, MA: Pearson Allyn and Bacon.
• Brothwell, D.R. 1982. Digging Up Bones: The Excavation, Treatment and Study of Human Skeletal Remains. Oxford: Oxford University Press. (There are many editions available.)
• White, T.D. 2000. Human Osteology, 2^nd edition. New York: Academic Press.
• White, T.D., and P.A. Folkens. 2005. The Human Bone Manual. New York: Academic Press.

Information on Identifying Mammal Bones in North America

• Gilbert, M.B. 1990. Mammalian Osteology. Springfield, MO: Missouri Archaeological Society.

Information on Procedures at Crime Scenes

• Geberth, V.J. 2006. Practical Homicide Investigation. Boca Raton, FL: CRC Press.
• Saferstein, R. 2007. Criminalistics. Upper Saddle River, NJ: Pearson Prentice Hall.
• Sullivan, W.T. 2007. Crime Scene Analysis. Upper Saddle River, NJ: Pearson Prentice Hall.

Assessment of the efficacy of this case study

• Scharf, E.A. 2006. Strategies for Teaching MNI, NISP, and Optimal Foraging Theory to Undergraduates. Poster presented at the 71^st Annual Meeting of the Society for American Archaeology, San Juan, Puerto Rico.

Acknowledgements: This case was published with support from the National Science Foundation under CCLI Award #0341279. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Date Posted: July 02, 2009.

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