The Analysis of a Murder, a Case Study

Instruction in chemistry has begun to shift away from the traditional lecture approach toward more student-cen- tered, active-learning methods. Peer-led instruction (1), prob- lem-based learning (2), guided-inquiry learning (3), team learning (4), and case-study teaching (5) are prominent among these pedagogies. Case study-based instruction is common- place in fields such as business, law, and medicine but it is relatively rare in the physical sciences, particularly chemistry. Recently, however, the NSF-supported, web-based, National Center for Case Study Teaching in Science (6) has been cre- ated as a vehicle for the dissemination of science-based case studies. The Center has greatly enhanced the use of case-based instruction in the sciences. At this college, case-based experiments are being used in our teaching laboratories to make laboratory instruction more interesting, challenging, and relevant to our students. Case studies are stories designed to engage students and convey a pedagogical message. They are useful to teach course content in an interesting manner and to clearly demonstrate the real- world significance of the content that the students learn. A well-written case requires the use of higher-order thinking skills than those required by conventional laboratory ap- proaches. The Analysis of a Murder case study was originally de- veloped for an analytical chemistry course and has been ex- tended to teach data handling and analysis in a non-laboratory context. When using the case in the latter manner, students are given pre-prepared dry-lab data and asked to properly analyze and apply the results. A data set designed for use this way is included in the Supplemental Material.W In this latter form, The Analysis of a Murder case study is suitable for use in general chemistry or nonscience major chemistry courses. Summary of The Analysis of a Murder Case Study A worker discovers the nude, limbless, headless torso of a dark-skinned, young boy floating in London's River Thames. Signs indicate that the boy, named Adam by the police, ap- parently was the victim of a ritual sacrifice. Two Scotland Yard detectives immediately begin a search for Adam's identity and his place of origin. Expert analysis of pollens found in Adam's stomach indicates that they are not of local origin, and the fact that the pollens have not been completely digested indi- cates that he had only been in London for a short time prior to his death. One of the detectives knows of a University of London professor whose research focuses on the distribution of strontium in soils, worldwide. He speculates that the professor's worldwide strontium concentration data base may be able to help them identify Adam's region of origin. The police contact him and ask whether he could aid them in lo- cating Adam's region of origin. Working together, the team uses a synergistic combination of solid analytical chemistry and creative detective work to pin down Adam's country of origin to Nigeria. After gathering an assortment of Nigerian bone samples and determining their strontium concentration, the team further narrows Adam's region of origin to a spe- cific, small area of that country. At this point in the case, the students are told that it is their turn to take over the investigation. They are provided with a map of Nigeria (7), strontium-doped artificial bone samples "collected from specified regions of Nigeria", and a sample of "Adam's bone material" and are asked to determine its strontium concentration. After using their experimental data to determine Adam's region of origin, the students as- sume the role of detectives and formulate a strategy to use these data to identify the persons responsible for Adam's mur- der. At the conclusion of their study, the students write a de- tailed account of their investigation to the chief inspector of Scotland Yard. The full text of the fictional case study that is based on