Structured Controversy: A Case Study Strategysciencecases.lib.buffalo.edu/cs/pdfs/Structured...

November 1996 JCST 95

Structured Controversy:A Case Study StrategyDNA Fingerprinting in the Courts

Clyde Freeman Herreid

Clyde F. Herreid is a DistinguishedTeaching Professor in the departmentof biological sciences, State Universityof New York at Buffalo, Buffalo, NY14260-1300.

Continuing JCST’s series on case-study teaching, we introduce a dynamic form of the case-instruc-tion method that involves debate and compromise. It is suitable wherever there is a controversialissue at hand.

Science has always been filled withcontroversy whether the issue isthe Big Bang hypothesis versus

the steady state universe, the cold fu-sion debate, or the wave versus particletheories of the nature of light. It is thenature of the business to question, de-bate, and argue. Science is not specialin that regard. Human society as awhole is besieged by debate and prob-ably always has been. It is personifiedby Adam and Eve arguing with the ser-pent. It is Galileo Galilei at the Inqui-sition. It is Bob Dole versus BillClinton.

Formal debate technique is part ofa lawyer’s arsenal. The seeds of theadversarial approach to problems aresewn in law school classrooms, nur-tured in moot courtrooms, and reachfull bloom in the criminal and civilcourthouses of America. Whatever elseit does, the adversarial system honesthe wits of the participants and bringsthe issues of any problem into sharpfocus. However, it leaves little roomfor compromise. Indeed, it seems thedebaters are often more interested inwinning the argument than seekingjustice or truth. Furthermore, much oflife is not a zero-sum game where thereis a winner and a loser. Many wouldargue that cooperation and negotiationtowards a compromise is a bettermodel for life. In fact, many of thegreat debates in science ended with acompromise solution, which brings us

to the technique at hand.Structured controversy is a teaching

technique that uses the strengths ofconventional debate and ends with twosides seeking ways to resolve the con-flict through compromise. Its virtues inthe classroom have been championedand summarized by Johnson andJohnson (1989) and Johnson, Johnsonand Holubee (1992). Compared tomost other methods of instruction,structured controversy results in greaterstudent mastery and retention of thematerial and a greater ability to gener-

alize the principles learned (Johnsonand Johnson, 1988).

There are at least four major criti-cal thinking skills required by the con-troversy structure (Johnson andJohnson, 1989, 1992):▲ Students must collect data and ana-lyze the research in order to presentevidence supporting a position.▲ Students must evaluate and criticizethe opposing position using rules oflogic and evidence. At the same time,they must repel the attack of their op-ponents and shift and refine their ownpositions.▲ Students must see the issue fromboth perspectives.▲ Finally, students must synthesize andintegrate the best evidence from bothsides and reach a compromise consis-tent with both positions.

TWO VERSIONS OF STRUCTUREDCONTROVERSY

Johnson, Johnson, and Holubee(1992) summarize the major steps usedin structured controversy in the classroom.

* * *▲ First, a controversial topic is pro-posed by the instructor (e.g., nuclear

The now familiar image of the doublehelix.

Copyright © 1996, National Science Teachers Association (NSTA). Reprinted with permission from Journal of College Science Teaching, Vol. 26, No. 2, November 1996.

96 JCST November 1996

The structured controversymethod is excellent

for dealing with casesthat are highly chargedand should be added

to the list of techniquesfor teaching case studies.

It forces all parties toanalyze the best evidence

on both sides of thequestion and then

to search actively fora compromise solution.

power plants should form the basis ofour nation’s energy policy; e.g, loggingoperations should cease in our nationalforest and parks).▲ Second, students are coupled in pairs(teams) to research literature and pre-pare arguments for either the pro orcon side of the issue.▲ Third, opposing teams meet and givetheir “best case” arguments to one an-other, courteously debating the issue.▲ Fourth, the opposing teams reversetheir roles presenting the opposite viewas convincingly as possible.▲ Fifth, the opposing teams abandontheir advocacy roles and write a com-promise report.▲ Sixth, all individuals in the class takea written test based on the material andreceive bonus points if all members oftheir compromise team score over a setcriterion.▲ Seventh, the teams give a 10-minuteoral report on their compromise to theclass with all team members participat-ing.

* * *Johnson and Johnson’s Structured

Controversy method is a powerful tech-nique that can be applied to case studyteaching. It clearly achieves the learn-ing goals I summarized earlier.

Nevertheless, the technique requiresa large investment of classroom time;six class periods are recommended.Barbara Watters of the State Univer-sity of New York at Oswego (personalcommunication) has recently devel-oped an alternative approach thatmeets many of the above goals, yet itcan be accomplished in one or twoclassroom periods. It requires a mini-mum of 75 minutes to complete.

Watters’ model works this way:▲ First, a controversial topic is as-signed.▲ Second, each student working on hisown searches the literature and writestwo position papers, one for the proand another for the con side of thecontroversy.▲ Third, during class, small groups ofstudents are formed. Half of thegroups are asked to role-play the proside and half are asked to role-play thecon side. Each group chooses its three

debate. This process is repeated withpro and con teams alternating their ar-guments.▲ Fifth, the instructor asks the groupsto abandon their advocacy roles and totry to come up with a compromisestatement that might be found reason-ably acceptable by the opposinggroups. These solutions are listed onthe board with commentary by eachgroup.▲ Sixth, the instructor or a studentcloses with a summary analysis.

The structured controversy methodis excellent for dealing with cases thatare highly charged and should beadded to the list of techniques forteaching case studies (Herreid, 1994).It forces all parties to analyze the bestevidence on both sides of the question

and then to search actively for a com-promise solution. The method is bestunderstood by showing an example ofa recent case using the DNA finger-printing which received notoriety inthe O.J. Simpson murder trial.

When using this technique, the in-structor must be sure to give clear in-structions in order to get good writtenand oral responses. Students must un-derstand how to write individual po-sition papers on the pro and con sidesof arguments and the proper rules ofdebate conduct.

To start the students out with theright strategy, I give them handouts onthe Elements of Argumentation, whichis drawn from Govier (1992), Hin-derer (1992), and Zeidler, Lederman,and Taylor (1992). Then, I assign atopic with instructions on how to pro-ceed. I also include an abbreviated ex-ample of a student paper on a differ-ent topic.

For the readers of the Journal forCollege Science Teaching, I am includ-ing an example of the use of DNA fin-gerprinting in forensic medicine,which follows this article. ❏

This work was supported by a grantfrom the Fund for Improvement ofPostsecondary Education, U.S. De-partment of Education.

ReferencesGovier, T. 1992. A Practical Study of Argument. 3rd

ed. Belmont, CA: Wadsworth Publishing Co.Herreid, C.F., 1994. Case studies in science–A novel

methodof science education. Journal of College Sci-ence Teaching 23(4): 221-229.

Hinderer, D.E. 1992. Building Arguments. Belmont,CA: Wadsworth Publishing Co.

Johnson, D.W. and R.T. Johnson. 1988. Criticalthinking through controversy. Educational Lead-ership May 1988: 58-64.

Johnson D.W. and R.T. Johnson. 1989. Cooperationand Competition:Theory and Research. Edina, MN:Interaction Book Co.

Johnson, D.W. and R.T. Johnson. 1992. CreativeControversy: Intellectual Challenge in the Classroom.Edina, MN: Interaction Book Co.

Johnson, D.W., R.T. Johnson, and E.J. Holubec.1992. Advanced Cooperative Learning (Revised).Edina, MN: Interaction Book Co.

Zeidler, D.I., N.G. Lederman, and S.C. Taylor.1992. Fallacies and student discourse: conceptual-izing the role of critical thinking in science edu-cation. Science Education 76: 437-450.

best arguments.▲ Fourth, the instructor then calls ona pro side group to present its top ar-gument, identifying its assertion andevidence to support it. Con-groupmembers are asked to comment on thepro argument. Rebuttal is permitted.Then, a con-group presents its best ar-gument. Pro commentary follows with



Write an analysis paper of the arguments surround-ing the use of DNA evidence in courts of law. In orderthat you gain an understanding of both sides of the is-sue, and acquire experience in identifying assertions andevidence, please structure the paper in the followingmanner.

TITLE: e.g., DNA Evidence Should be Used in Fo-rensic Medicine

AUTHOR · Your name

INTRODUCTION: Several sentences briefly intro-ducing the controversy.

PRO-SIDE OF THE ARGUMENT: Here youshould lay out four of the major assertions and evidencethat would be used in arguing in favor of the proposi-tion stated in the title.

A note on assertions: Those that are short are oftenmore easily defended than longer, more complex asser-tions. Good assertions are falsifiable in principle; i.e., theycan be tested and we will know if they are wrong.

A note on evidence: Be sure that the evidence thatyou use speaks directly to the assertion you make andmeets the conditions of a good argument: the evidencemust be adequate, relevant, and succinct. Finally, whenyou refer to data in the literature, proper citations shouldbe appended to the paper.

CON-SIDE OF THE ARGUMENT: Here, youshould write four major assertions and offer supportingevidence against the proposition in the title, using ref-erences where appropriate.

POSSIBLE COMPROMISES: Here, try to find anycompromise statements or positions that both sides ofthe argument might agree to include.

PERSONAL OPINION: Write your personal viewson the proposition.

REFERENCES CITED: Write out complete refer-ences to papers that you have cited.

A short version of a student paper follows.

DNA EVIDENCE SHOULD BE USED INFORENSIC MEDICINE (shortened version of a studentpaper)

INTRODUCTION: Technology concerning DNAfingerprinting has been developed for use in forensics.However, some believe this technology is unreliable andmay in fact cause a false positive reaction, thus causingthe imprisonment of an innocent person. The admissionof DNA evidence into court has been extremely contro-versial, as was seen in the O.J. Simpson case.

PRO: Yes, DNA fingerprinting should be used in fo-rensic medicine.

ASSERTION 1: DNA-based identification is morereliable than other forms of identification, such as bloodgroups and enzymes.

EVIDENCE 1: “If enough tissue or semen is avail-able, forensics laboratories can perform tests to determinethe blood or tissue type. However, such tests havelimitations...there are many people in the populationwith the same blood type or tissue type...this approachcan only exclude a suspect...DNA testing, on the otherhand, can theoretically identify the guilty individual withcertainty because the DNA base sequence of every indi-vidual is unique” (Campbell et al., 1994).

“DNA-based identification has been so widely em-braced by the judicial system because...a suspect can for

Structured Controversy: ACase Study Strategy: Part IIStudent Assignment: An Example of the Use of DNA

Fingerprinting in Forensic Medicine

Clyde Freeman Herreid



all practical purposes be positively identified” (McElfreshet al., 1993).

“Another problem with traditional forensic methodsis that, during the weeks or months [of the investiga-tion], evidence may have to wait before being examinedby a forensic scientist and proteins can become degradedor denatured so their antigenic properties are lost. Forexamination in forensic samples, DNA is more suitablethan protein because DNA remains intact in the envi-ronments where such evidence generally is found. In-deed, small fragments of human DNA have been iso-lated and cloned from the tissue of a 2,400-year-oldEgyptian mummy. Although the length of these DNAfragments was too small for RFLP analysis, this workdoes illustrate the impressive stability of the DNA mol-ecule” (Moody, 1989).

ASSERTION 2: Statistical analysis has shown that itis almost impossible for two people to share the sameDNA unless they are identical twins.

EVIDENCE 2: No two people have the same DNA(nucleotide sequence) unless they have an identical twin(Campbell et al., 1994). Even family members do notcarry an identical genetic make-up. They share some ofthe markers, but there are genetic differences that are spe-cific to each person (McElfresh et al., 1983). The mainpurpose of DNA based-identity is to take evidence andcompare the similarities or differences to that of the sus-pect.

DNA tests are so variable that “an almost infinitenumber of genotypes across several loci can be identi-fied” (McElfresh et al., 1993).

Inheritance of DNA patterns is independent amongloci, thus the probability of each is multiplied to findthe total probability. “It is not unusual for a four-locusDNA pattern to have individual loci with average prob-abilities of a 1 in 100 and therefore a combined prob-ability of .1 in 100 million” (McElfresh et al., 1993).

ASSERTION 3: DNA fingerprinting is generally ac-cepted by the scientific community.

EVIDENCE 3: “In most states, scientific evidence isadmissible only when it has ‘gained general acceptance’in the scientific community” (Witkin, 1994). “ForensicDNA testing has been adopted not only throughout theUnited States, but in Canada, Europe, and elsewhere.Similarly, paternity testing, which uses identical meth-odology, has been accepted for years” (Devlin et al.,1993). DNA fingerprinting has met with the require-ments of scientific evidence allowable in court.

DNA fingerprinting, as the process is called, is a com-plex, high-tech forensic test that can link a suspect tothe commission of a crime - or establish his innocence.While still controversial, use of the test is gaining accep-tance in American courtrooms” (Cray, 1994).

* * *CON: No, DNA fingerprinting should not be used

in forensic medicine.

ASSERTION 1: There are inherent errors in the tech-niques used to determine a DNA fingerprint.

EVIDENCE 1: Possible sources of error include bandshift, DNA degradation, partial restriction digesting, andinconsistencies in the electrophetic gel. “Forensic samplesare different in origin, storage, and collection from thestandards. Such differences between the samples may bereflected in mobility differences between the DNAbands. It is just as probable that band shift could moveaway from a match as into one, and there is no way topredict which will happen” (McElfresh et al. 1993).

In the RFLP method, restriction enzymes break theDNA strands at specific sites, resulting in variable frag-ment lengths between individuals. However, “heat, hu-midity, bacterial contamination, and UV light damageDNA by causing random breakage of the helix”(McElfresh et al., 1993). This will result in random frag-ment lengths that may cause errors in the DNA finger-print produced. Slight inconsistencies in the electro-phoretic gel can skew the positions of the DNAfragments. “Occasionally, restriction bands do not sepa-rate completely, or they end up at slightly different po-sitions in different gels” (Campbell et al., 1994).

In addition to the inherent errors in the techniques,there is always the possibility of human error. “The larg-est source of error lies in poor laboratory practices” (Rob-erts, 1992). “The lab error is the most likely place to geta false incrimination of an innocent person or a guiltyperson going free” (Nowak, 1994).

ASSERTION 2: A lack of consensus is often evidentwhen interpreting DNA typing results.

EVIDENCE 2: Each forensic lab has defined its own“match criteria.” LIFECODES Corp. of Stanford, Con-necticut has established that two bands would be de-clared a match if they fall within 2.8% of each other insize. This is based on their calculated standard deviationwhich derives from empirical data. The FBI has deter-mined that, based on their empirical data, matchingbands exist if two bands are within 2.5% of each other



in size (McElfresh et al., 1993).Lack of defined protocol or criteria leads to a lack of

consensus in interpretation. In a 1989 court case, aLIFECODES Corp. forensic scientist calculated the oddsof a random match between the evidence and the sus-pect to be one in a million. Other forensic scientists whoexamined the same data calculated the odds to be onein 24 (Neufield and Colman, 1990). “Most scientistswith training in molecular biology and population ge-netics would accept DNA typing as probative, but mostalso view it with some caution since it involves theconfluence of many theories and techniques” (Ayala andBlack, 1993).

ASSERTION 3: DNA evidence is at best circumstan-tial.

EVIDENCE 3: All DNA evidence admitted to courtconsists of a “visual/measured interpretation of the pat-tern of DNA bands on the autoradiography and if thepatterns have been declared to be the same, a mathemati-cal declaration of the probability of finding that DNApattern in a given population” (McElfresh et al., 1993).These probability estimates are a function of the num-ber of VNTR loci examined but “the variation in thefrequencies ranges from one in 400,000 to one in4,000,000” (McElfresh et al., 1993).

It is interesting to note that, while these probabilityestimates for a perfect match may be compelling, up to400,000 people can expect to pass within 10 blocks ofa rape incident in New York City’s Central Park on atypical business day, and 4,000,000 people within threemiles of the crime. Viewed in this light, when the sus-pect falls within the “high probability” range of beingthe perpetrator, it becomes problematic to correlate “highprobability” with “highly likely” without taking into ac-count such things as population density within the areaof the crime scene.

Circumstantial evidence “consists in reasoning fromfacts which are known or proved to establish such as areconjectured to exist” (Black’s Law Dictionary, 1990).Now, it is a relatively simple matter for scientists to es-tablish the “fact” that the probability of a given suspectcommitting a crime is one in 1,000 or one in 2,000,000,but given this fact, it is still necessary for a jury to infer,given other evidence, that this probability is compellingenough to establish guilt. By definition, then, since es-timates of genotype probabilities are, as yet, never equalto one, the legal community must (through conjecture)establish guilt or innocence via other evidence. DNA evi-dence is thus circumstantial at best.

POSSIBLE COMPROMISE: Statistical analysisshows that the probability of a false positive match var-ies from one in 400,000 to one in 4,000,000 people. Al-though at first this number seems sufficient enough toconvict the suspect, when considering that 4,000,000people can be found within a small geographical regionin densely populated areas, this ratio becomes unconvinc-ing. Therefore, DNA evidence can never prove with cer-tainty the guilt of a suspect.

In light of this, DNA evidence should be used onlyto corroborate other evidence to implicate a suspect or,conversely, to exonerate that person. Further, regulationsshould be passed and enforced establishing universaltechniques and standards in processing DNA. Thiswould include private and FBI labs.

PERSONAL OPINION: We believe that DNA fin-gerprinting is a very useful tool in the field of criminaljustice. It has been shown to be very powerful and exactin determining the identification and guilt or innocenceof a suspect. Like any method, however, DNA finger-printing is subject to error, and these possible fallaciesmust be regulated and insured against to warrant the va-lidity of DNA testing.

We feel that research should be conducted to definethe frequency of a particular DNA fingerprint occurringin the population in order to reach consensus in the sci-entific community, that DNA tests should be standard-ized to avoid the scrutiny that follows due to variationsin methods and results, and DNA labs should be regu-lated, either by the federal government or some otherbody, to insure the exactness and validity of results.

ReferencesAyala, F. and J.B. Black. 1993. Science and the courts. American Scientist

May/June 1993: 233.Black, E. 1990. Black’s Law Dictionary. New York, NY: MacMillan Pub. Co.Campbell, N.A., L.G. Mitchell, and J.B. Reece. 1994. Biology: Concepts and

Corrections. Redwood City, CA: Benjamin/Cummings Pub. Co.Cray, D., 1994. Order in the lab. Time 8 August, 1994: 46-47.Devlin, B., R. Nail, and K. Roeder. 1993. Statistical evaluation of DNA fin

ger printing: a critique of the NRC’s report. Science 5 February, 1993: 748-749, 837.

McElfresh, K.C., et al. 1993. DNA-based identity testing in forensic science.Bioscience March 1993: 149-157.

Moody, M.D. 1989. DNA analysis in forensic science. Bioscience January1989: 31-35.

Neufield, P.J. and N. Colman. 1990. When science takes the witness stand.Scientific American May 1990: 47-48.

Nowak, R. 1994. Forensic DNA goes to court with O.J. Science 2September 1994: 1352-1354.

Roberts, L. 1992. DNA fingerprinting: academy reports. Science 17 April1992: 300-301.

Witkin, G. 1994. Science takes the stand. U.S. News and World Report 11July1994: 29-31.



(Continued from page 96)

TEACHING NOTE

IS THIS REALLY A CASE?I have called this a case-study

method and in spite of the facts, theapproach does not appear to tell astory. Yet, because the assignment is inthe context of the O.J. Simpson civiltrial, there is an underlying story line.Nothing more is needed for the stu-dent. In the student paper and in theclassroom debate which follows, thetrial pervades.

In addition, I set up a story contextin two other ways. First, I gave the stu-dents handouts or literative referencesto the O.J. Simpson trial where expertwitnesses debate the problems of DNAfingerprinting. Students are told theymust include additional references ifthey are to receive an “A.” Second, Ido a “lab exercise” marketed by Ward’sScientific which is a “DNA Whodunitkit” designed for 30 students. It con-sists of a hypothetical murder mysteryinvolving the “blood” from a victim,a murderer, and five suspects. Stu-dents, using popbeads, first buildDNA models which vary among thesuspects. Then they proceed to gothrough simulated steps of the DNAfingerprinting process with “restrictionenzymes,” “electrophoresis,” and “ra-dioactive probes,” finally identifyingthe murder. College students in myEvolutionary Biology course foundthis exercise exciting and it can bedone in any classroom in a period of75 minutes. Together with the struc-tured controversy assignment, there isno doubt as to the story line.

BLOCKS OF ANALYSISIn a traditional case study where the

instructors include an extensive de-scription of a particular murder or di-lemma, traditional blocks of analysiswould be found here. But this is notabout the O.J. Simpson trial or anyother trial. The student has been askedto write a series of assertions and evi-dence statements using the literature,some of which the instructor may nothave seen. Consequently, there is the

possibility of more surprises with thestructured controversy approach thanwith most other case study teachingmethods. Yet, there are still clearblocks of analysis which we can predictgiven that the case is to be used in ascience class.

DNA STRUCTUREThis case, especially if the instruc-

tor uses the “Whodunit Kit,” providesclear opportunities to get the DNAstructure indelibly printed in the mindof the student. This will not likelycome up directly in the debate unlessthe instructor asks the students toclarify or amplify some points of evi-dence. But if the instructor spends toomuch time asking questions on this orany other point, the spontaneity anddrama of the debate itself is easily lostand the instructor reverts to the role ofSocratic discussion leader.

DNA FINGERPRINTINGThere exist excellent drawings, de-

scriptions and models of the varioussteps of the DNA fingerprinting pro-cess. If these are made available to stu-dents in the handouts, there should belittle difficulty understanding the pro-cess. Questions about the method,however, frequently appear in the de-bate, as do questions about the use ofPolymerase Chain Reaction (PCR) inamplifying nucleotide chains and theuse of electrophoresis and probes.

GENETICSThe structural discussion of DNA

is a natural platform to discuss variabil-ity in the genome and the uniquenessof the individual. Topics of mutation,junk DNA, and hypervariability lurknot far behind, along with the use ofDNA fingerprinting to detect geneticdisorders and gene replacement.

ETHICAL CONSIDERATIONS OF GENETICENGINEERING

Screening methods for genetic dis-ease and the potential for gene therapynaturally evolve into questions of“What do we do with this informa-tion?” Are abortions an option if wedetect an abnormality? Do we inform

patients? Employers? Insurance agents?Will we permit individuals to manipu-late their childrens’ genetic makeup atwill? These questions, although off themainline of DNA fingerprinting, areclose at hand and it will take an alertinstructor to avoid some of these issuesif they are not on the agenda for dis-cussion.

THE USES OF DNA FINGERPRINTINGBy now the public knows that mur-

ders and rape and paternity cases canbe solved with a small amount ofDNA. Less well known is the role ofDNA in detecting evolutionary rela-tionships, determining family connec-tions in animals, and identifying ani-mal carcasses in cases of poaching ofendangered species. These topics areinteresting sidelights to the case.

A part of these discussions will fo-cus on the issue of misidentification,which is an especially grievous error incriminal cases. Lab procedures, securitymeasures, and cross-checking betweenlabs are all discussion points, as arequestions about how the age and con-dition of a sample can affect analysis,how band shifting might occur onelectrophoresis gels, and how clearlyDNA fragment lengths can be identi-fied (“The bin size problem”).

PROBABILITY THEORYMuch of the discussion involving

DNA fingerprinting centers on theprobability of making a correct matchof suspect to murder. This issue istouched upon in the accompanying stu-dent paper. An extensive analysis of theprobability of finding matches in certainethnic groups is central to the discus-sion. It will be important for the in-structor to ask how we can decrease thechances of making such an error. Partof the answer should be to increase thenumber of identifying probes. Certainto be part of the discussion will be howone calculates the probability of a matchand the use of the “product rule.” Theconflict involving the use or non-use ofthe “ceiling principle” advocated by theNational Research Council is appropri-ate here.

In a normal discussion case found



in law or business schools, these blocksof analysis would be managed in con-trolled ways by the instructor. Consid-erably less control exists with struc-tured controversy cases.

RUNNING THE CLASSOne of the greatest strengths of

structured controversy is that the stu-dents come to class highly prepared.They have studied the literature andwritten papers on both sides of the ar-gument and therefore know the issues.

At the beginning of class, after briefintroductory remarks by the instructor,teams of four or five students shouldbe rapidly assembled. (In classes wherecooperative or collaborative learning isroutine, groups probably already exist.)After this, the instructor splits the classin half, perhaps by drawing an imagi-nary line down the center of the room.Teams to the left of the line are as-signed the pro-side of the argumentand teams to the right are assigned thecon-side. The instructor tells eachside’s teams to decide upon three oftheir best arguments (assertions andevidence). This takes about 20 min-utes.

The instructor working at thechalkboard or overhead projector asksone of the teams from the pro-side tomention its first assertion and evi-dence. The instructor writes this downrapidly in an abbreviated form, then heasks for comments from the con-sideof the room. There will usually be sev-eral groups volunteering to criticize thepro-argument. Normally, they willchallenge the quality or quantity of evi-dence or present counter-evidence.

Sometimes there will be challengesto the chain of reasoning used - falla-cies of logic exposed. It is remarkablehow vigorously students will argue androle-play a particular position whichmay be contrary to their personalviews. Instructors can either lay backand let the debate rage or interveneperiodically. I recommend interven-tion.

Students have a hard time concen-trating on one particular assertion andits evidence. They often want to bringup other arguments and broaden the

debate. If this tendency is not stopped,the debate will spin out of control andlittle will be accomplished. So, the firstjob of the instructor is to keep the dis-cussion focused on the assertion andevidence on the board. The second jobis to see that the advocacy role is nottaken so seriously that students beginto act like Perry Mason, delivering im-passioned speeches to the jury. The in-structor must stop them from using adhominem attacks and jibes. The thirdjob is to look for opportunities to helpdevelop particular points about key is-

sues. This should be done by askingappropriate questions rather than stop-ping the discussion and delivering amini-lecture.

After the pro-side has given one oftheir arguments, members of the con-side are asked to discuss one of theirs.Again, the instructor writes the asser-tion and evidence on the board. Thenhe asks for commentary from the pro-side and friendly debate should follow.This process is repeated one or twomore times, alternating between thetwo sides. This phase of the classshould be finished 20 minutes beforethe classes ends.

The instructor then asks the teamsto leave aside their advocacy roles. Thestudents are instructed to come up

with at least one suggestion for a com-promise between the two sides. Aftera five minute discussion, the instruc-tor should list these on the board ei-ther with or without soliciting com-ment by other teams. If commentaryis accepted, be prepared for periodicoutbreaks of debate to erupt again.This may not be productive, especiallyif you are under a time constraint andare trying to close the discussion.

If time permits, the instructor couldtry a more interesting and fruitful wayof compromising. He tells each team

to send half of its members to the op-posite side of the room. Thus, he endsup with new teams composed of halfpro and half con members. The in-struction to these new teams is to lookfor at least one compromise positionon which they might agree. After a fewminutes of discussion the instructorasks for the teams to report on theirsuccesses. This serves as a nice finale tothe discussion.

Acknowledgment: This work was sup-ported by a grant from the Fund for theImprovement of Postsecondary Educa-tion, U.S. Department of Education.

Video photography of assembled karotypes


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