WHO DONE IT?
Liz Fulton, Carol Alderman, Carol Sanders
1993 Woodrow Wilson Biology Institute
Techniques involved in DNA analysis, blood typing, fingerprinting, skeletal anatomy, chromatography, soil and textile analysis, spectrophotometry
Minimum of 3 hours but could be expanded to a week or more
Materials may be as simple as a labeled diagram of the skeleton for bone identification or as complex as a gel electrophoresis setup
Depends on activities selected. Check state guidelines concerning use of body fluids
Varies with activities selected. Advance preparation must be made to set up mystery components, expert witness folders, suspect file, and rules for data collection and arrest
Everyone loves a mystery, so put your students to work using various scientific methods to solve a murder or series of murders. This highly variable activity can be structured to your number of players, time limits, grade level, materials, etc. Solving a murder requires utilization of critical thinking skills that will integrate several science disciplines and flow across the curriculum.
Teams investigate evidence from which they must build a logical case to implicate one of several possible suspects. Give students as little direction as possible beyond the original data so they may experience science through discovery.
A beginning scenario might have student detectives describe the victim(s) and crime type and then look for trends and patterns. For instance, the presence of a female body and/or several female skeletons of similar size might indicate a serial killer who preys on a certain type of woman. Broken hyoid bones could represent death by strangulation or a murder weapon could be present. Another approach would start with students acting as crime lab personnel who analyze a written crime scene description, construct an assailant profile, then identify the killer.
Groups can work together to share information or compete to identify and investigate suspects. Each team might have experts (fingerprint, blood type) who meet with experts from other teams to share data or who simply interpret data for their own team. If groups are at a loss as to how to proceed, you may offer suggestions or refer them to the expert witness folders.
The number of fingerprints, DNA, blood or saliva samples students are allowed to take from suspects should be limited. This means they must make good use of skeletal material, hair samples, casts or other available data. Teams may be given one warrant for the arrest of their hypothetical killer. This warrant should be signed by the suspect with date and time of arrest noted, then returned to you. When all warrants are issued, the winning team is announced.
II. MYSTERY COMPONENTS
- Suspect file containing biological data and "criminal records".
Information will be added during the investigation. Suspects could include students, their families, and agreeable faculty members (including yourself). Possible information for suspect sheets: photograph, coloration, height, weight, birthday, blood type, distinctive features, fingerprints, aliases, and prior convictions.
- Practice solving mysteries by sequencing events in a crime or through use of prepared kits such as Ward's DNA Whodunit Kit.
- Set/describe the crime scene.
An anonymous phone call or letter reports a murder and its location (school ground or nearby field). Students can visit the crime scene and compile evidence or a written description along with photographs and exhibits can be provided.
Choose from the following suggestions or devise others. Students must determine what evidence is from victim, killer, innocent bystanders, or even animals that have been around the area.
- Body-volunteer, CPR dummy, old department store mannequin.
- Partial skeleton(s). Pelvis indicates sex; femur indicates height; digits indicate age. Other informative bones are vertebrae, ulna, radius, humerus, or sternum.
- Murder weapon. Knife with one or more "blood types" (killer's on handle, victim's on blade); fingerprints; maybe strands of hair. Simulated blood can be provided in vials for typing or DNA analysis. Animal blood can be used for effect, but will not react to human typing sera.
- Fingerprints. Determine print classification and match to suspect. Fingerprint position on weapon determines which finger(s) you have.
- Plaster casts or photographs of footprints, handprints, kneeprints, etc. Indicate height from stride length, weight from print depth. Students may construct graphs that relate body measurements.
- Hair samples. Use microscopes to observe color and texture. Do DNA analysis of proteins.
- Textile threads, pieces of cloth or buttons from the assailant's clothing, perhaps with blood stains.
- Soil or other materials left in prints, on clothing or on victim. Match to a certain location (river clay) or occupation (potter).
- Scrap of note with ink. Use chromatography or spectrophotometry analysis to compare ink with that of pens belonging to suspects. The note may also be used to do a handwriting analysis.
- Saliva on glass or straw for blood typing of secretors.
- Tape recording of disguised voice threatening the victim for voice print ID.
III. "EXPERT WITNESS FOLDERS"
- Bone up on bones.
Labeled drawing of human skeleton; comparison of male and female pelvis; skeletal relationships (2.6 X femur length in cm + 65 = ht in cm, X 0.4 to convert to inches); fact sheets (bone density, presence of growth zones or scar patterns indicate age or injury); proportion relationships (arm span = height); environmental contaminants present (excess exposure to lead and fluoride).
- Gene screen.
Provide procedure for DNA fingerprinting using gel electrophoresis of blood, semen, hair or other body samples. Include pictures of DNA sequences that can be used to practice matching bp patterns. Students can use crime scene samples (blood from knife) and actually run the gels, then compare the DNA sequences to determine which suspect matches the assailant, or they can work with previously prepared photographs. Prepared photographs of gel runs insure a good match, save time, and you can substitute bacterial or viral DNA for human DNA.
- Type that blood.
Description of blood cell structure, presence of surface proteins and blood antibodies; procedure for A,B, O and Rh typing; description of secretor/nonsecretor determination from saliva.
- It's a print.
Description of fingerprint lifting and identification. Taping suspect prints to overhead transparencies allows the entire class to view them at once.
- Hair care.
Electron micrographs and light microscope photographs or prepared microscope slides of various colors and textures of hair.
- Think ink.
Description of paper chromatography or spectrophotometry techniques to identify pigments in different types/brands of ink.
- Soil toil.
Geological data on soil types in the murder area.
- Truth in casting.
Tips on how to do plaster casts and what you can deduce from them.
- Who knows.
Collection of articles discussing new technologies in crime detection and their impact on the courts.
SETTING THE CRIME SCENE
On an ordinary day in the classroom an extraordinary thing happens. The office phone rings, you answer, students listen surreptiously while pretending to be absorbed in their reading assignment.
Quickly you relate to them what you have just learned from the chief of police. A body has been found on the vacant lot across from the school and the police need investigative help. Having studied varied topics including skeletal anatomy, DNA analysis, and blood physiology your class is well prepared to offer this help, so you pack up your crime scene kit and head for the action.
Once on the scene your detective teams survey the area, then begin to collect evidence. Next to the body of a short blonde woman lies the apparent murder weapon, an ice pick. Dark hairs cling to the drying blood on both handle and pick, fingerprints are clearly visible on the sticky handle.
A heavy rain fell last night causing footprints to show in the soft dirt. Two sets appear to approach the body, with only one set moving away. Within the outlines, tiny blobs of red clay stand out against the lot's dark rich soil.
Several places around the lot appear to have been recently disturbed. Excavation of these spots yields 2 partial skeletons which are carefully bagged for later study.
The chief shows you an anonymous note that arrived at headquarters just moments ago. The note, written in lurid purple ink, claims responsibility for this murder and several others.
After completing the crime scene investigation, you and your student detectives return to the classroom to begin evaluating the collected evidence.
A crime scene setup such as this is nice but not necessary. A written crime scene description can be distributed and the evidence presented to students as already collected, bagged and ready for their investigations.
DNA typing or fingerprinting is a technique accepted in many courts today as evidence in murder, rape, and paternity cases. Samples of DNA may be isolated from semen, blood, hair, or even skin left at the crime scene.
Experts are able to differentiate among samples left by the assailant, victim or innocent bystander because, except in the case of identical twins, DNA is unique to the individual.
Restriction enzymes are used to cut the DNA, which is run on an electrophoresis gel to separate the base pairs by molecular weight. Radioactive probes are then attached to the DNA segments and photographs taken. By comparing photographs of suspect DNA with that found at the crime scene, experts can determine very accurately whether or not a certain person could be guilty of the crime.
Some courts have refused to accept DNA fingerprinting evidence because of the possibility of a false match. Statistical data indicates that by using four different radioactive probes, only two to three people in the world could possibly have matching DNA patterns. However, some people tend to marry within their race, culture, and geographic area increasing their frequency of a random match if an innocent suspect came from the same area and race as the guilty person.
A panel convened by the National Academy of Science calls for a laboratory accreditation program to be administered by the Department of Health and Human Services in conjunction with the Department of Justice to prevent/lessen the likelihood of mistaken identification due to lab error. The panel has also recommended the creation of a national committee on forensic DNA typing to follow developments in DNA testing, the creation of a DNA fingerprint database, and the development of federal and state policies for sharing DNA samples and information.
On this DNA fingerprint a stabbing victim's DNA profile(V) may be ** see hard copy for graphics matched to DNA extracted from blood to insert here on a defendant's(D) jeans and shirt. Size markers are found in the other lanes.
SAMPLE SUSPECT SHEET
ANYTOWN POLICE DEPARTMENT
Weight: 120 lbs
Name: Jane Doe (AKA "Teach")
Blood type: B+
Features: rose tattoo on left hip
Prior convictions: altering payroll checks for local high school teachers
Last known address: 6600 Apple Tree Lane, Anytown, U.S.A.
Being able to understand and organize evidence is an important part of solving crimes. The following group of statements was taken from the transcript of the Alonzo P. Merk murder trial. Somehow the court records have gotten all mixed up and must be put in correct order of events for the jury. Arrange the material as you feel it should be presented and be ready to defend your reasoning.
Fingerprints may be grouped into three sets of patterns, each bearing the same general characteristics. The patterns may be further divided into subgroups as follows:
ARCH LOOP WHORL
plain arch radial loop plain whorl
tented arch ulnar loop central pocket loop
Anatomy and chemistry texts and lab manuals.
Your state crime lab or state/local police: fingerprints, voice prints, handwriting analysis, DNA analysis, crime scene techniques, computer reconstruction from skulls, lie detector tests.
GEMS, Lawrence Hall of Science, University of CA, Berkeley, CA 94720: booklets on Crime Lab Chemistry; Fingerprinting.
WGBH, Box 2053, Princeton, NJ 08543, 800-828-9424; videos on Murder, Rape and DNA; Science of Murder.
ABT, Gordon Mendenhall, "Fingerprint Ridge Count," April, 1989, Vol. 51, #4.
BSCS, 830 N. Tejon St., Suite 405, Colorado Springs, CO 80903
4720: "Mapping and Sequencing the Human Genome."
NABT, 11250 Roger Bacon Drive, #19, Reston VA 22090: "A Sourcebook of Biotechnology Activities."
Wards: microscope slides of hair, blood stained fibers, fingerprints; kits for simulated blood typing and blood typing with saliva; DNA Whodunit Kit.
Carolina Biological: kits and manuals for fingerprinting, detection and typing of blood, electrophoresis materials.
DNA Science, 1990, Micklos & Freyer, Cold Spring Harbor, NY.
Ezell, C., "Panel OKs DNA fingerprints in Court Cases." Science News, vol. 141, April 25, 1992, p. 261.
The Science of Fingerprints, U.S. Department of Justice, FBI.
Franklin-Barbajosa, C., "The New Science of Identity," National Geographic, May 1992.