LEGAL ARGUMENTATION AND EVIDENCE ..........................9541$$ $$FM 07-24-0211:42:43 PS ..........................9541$$ $$FM 07-24-0211:42:43 PS L E G A L A R G U M E N TA T I O N A N D E V I D E N C E Douglas Walton the pennsylvania state university press university park, pennsylvania ..........................9541$$ $$FM 07-24-0211:42:44 PS LibraryofCongressCataloguing-in-PublicationData Walton,DouglasN. Legalargumentationandevidence/DouglasN. Walton. p. cm. Includesbibliographicalreferencesandindex. ISBN0-271-02177-2(cloth:alk.paper) 1.Law—Methodology. 2. Evidence (Law). 3. Logic. 4. Reasoning. I. Title. K213.W35 2002 347(cid:1).06—dc21 2001055956 Copyright(cid:1)2002ThePennsylvaniaStateUniversity Allrightsreserved PrintedintheUnitedStatesofAmerica PublishedbyThePennsylvaniaStateUniversityPress, UniversityPark,PA16802–1003 Thepaperusedinthispublicationisbothacid-free andtotallychlorine-free(TCF).Itmeetsthe minimumrequirementsofAmericanNational StandardforInformationSciences—Permanenceof PaperforPrintedLibraryMaterials,ANSI Z39.48–1992. ..........................9541$$ $$FM 07-24-0211:42:44 PS CONTENTS Acknowledgments ix Introduction xiii 1 SPECIALFEATURESOFARGUMENTATIONINA LEGALSYSTEM 1 LegalRulesandParticularCases 3 InterpretationofStatutesandDocuments 6 StagesofaTrial 9 CivilLaw,CriminalLaw,andBurdenofProof 11 Evidence 15 RelevanceandAdmissibility 19 TestimonyofWitnesses 23 ExpertTestimony 25 Examination 26 DependenceonPrecedents 29 2 FORMSOFARGUMENTCOMMONLYUSEDINLAW 34 ArgumentfromAnalogy 35 ArgumentfromanEstablishedRule 39 ArgumentfromSignandAbductiveArgument 41 ArgumentfromPositiontoKnow 45 ArgumentfromVerbalClassification 51 ArgumentfromCommitment 53 PracticalReasoning 56 ArgumentfromPersonalAttack(AdHominemArgument) 59 TheSlipperySlopeArgument 63 OtherImportantFormsofArgument 66 v ..........................9541$$ CNTS 07-24-0211:42:52 PS vi contents 3 CIRCUMSTANTIALEVIDENCE 73 TheMcCormickCriterion 74 TheJewishClassicalLawCriterion 77 BenthamonCircumstantialEvidence 80 Patterson’sCriterion 83 WigmoreonDirectEvidenceandAutopticProference 85 WigmoreonCircumstantialandTestimonialEvidence 88 TheHopeHeadCase 91 TheFiveCriteriaSummarized 93 HowUsefulistheConceptofCircumstantialEvidence? 97 LogicalDifficultiesofCircumstantialEvidence 99 4 PLAUSIBILITYANDPROBABILITY 103 AThirdTypeofReasoning 105 PlausibilityandProbability 108 WigmoreonLogicalInferenceandProbativeValue 114 LockeonPlausibilityandDegreesofAssent 122 BenthamonPlausibilityandEvidence 124 PlausibilityandCasuistry 128 PlausibleReasoningintheAncientWorld 133 Carneades’TheoryofPlausibility 138 CriteriaandApplicationsofCarneades’Theory 141 WhytheNeglectofPlausibleReasoning? 146 5 THEDIALECTICALFRAMEWORKOFLEGAL ARGUMENTATION 151 ImplicatureandConversationalPostulates 153 RationalPersuasionintheTrial 156 NormativeModelsofArgumentation 160 PersuasionDialogue 165 OtherTypesofDialogue 171 PeirasticDialogueandExtasticDialogue 174 RelevanceandDialecticalShifts 180 TheFairTrialandtheWitch-Hunt 184 ..........................9541$$ CNTS 07-24-0211:42:52 PS vii contents ADialecticalTheoryofStatutoryInterpretation 187 ArgumentationSchemes,Fallacies,andLegalLogic 194 6 APLAUSIBILISTICTHEORYOFEVIDENCE 199 ComponentsoftheNewTheory 200 EvidenceandArgument 205 TheProbativeFunction 214 AncientRootsoftheNewTheory 216 AdvantagesofThePlausibilisticTheory 223 ScientificEvidence 227 LogicalandLegalRelevance 230 LegalEvidence,Credibility,andPlausibility 234 ExpertTestimonyasEvidence 239 ProblemsandConclusions 243 7 RELEVANCEINPERSUASIONDIALOGUE 248 PersuasionDialogue 249 ChainingofArguments 252 RulesofDialogueandFallacies 258 TheFallacyofIrrelevantConclusion 260 TheMethodofArgumentExtrapolation 262 TestinganActualExample 266 HowtheMethodShouldbeApplied 269 QuestionsRaised 271 ApplicationtoLegalCases 274 ArgumentsandExplanations 279 8 MULTI-AGENTARGUMENTATIONANDCREDIBILITY 282 FormalDialogueSystemsinLogic 283 TheAdHominemandAdVerecundiamFallacies 287 LabeledDeductiveSystems 296 Multi-AgentSystems 298 AddingAgentstoFormalDialecticalStructures 301 EvaluatingFallaciesandBlunders 304 HowShould‘Agent’beDefinedinFormalDialectic? 306 ..........................9541$$ CNTS 07-24-0211:42:53 PS viii contents DialecticalShiftsandRelevance 308 TheSolutiontotheProblem 313 Conclusions 317 9 HOWTOUSETHENEWMETHOD 321 TheNewMethod 322 InferenceFormsandCriticalQuestions 325 ArgumentsDependingonTestimonyandCredibility 329 VerbalArgumentsandCriticalQuestions 334 TheTrialasPersuasionDialogue 335 ArgumentDiagramming 338 TheFormalStructureofDiagramming 342 FormalizingtheNewSystem 345 TheSubtletiesofPeirasticDialogue 348 TheCurrentProblemswithRelevance 350 Bibliography 357 Index 365 ..........................9541$$ CNTS 07-24-0211:42:53 PS ACKNOWLEDGMENTS Even though I have been working on legal argumentation and evidence for some time, and have written some papers on the subject, the idea that there was a need for a book on it was not at first apparent to me. What suggested suchanideawasavisitto NotreDameLaw SchoolinNovember 1997, when I gave an invited lecture on legal argumentation as part of a symposium on legallogic.Thesymposium,andindividualconversationswiththeparticipants, showedmetheneedforbringingtheresourcesofargumentationtheorytobear onfundamentalproblemsinevaluatinglegalreasoning.Inparticular,itseemed tomethatthekindofreasoningusedinevidencelawwasvirtuallyunexplored territory, from a logical point of view, that badly needed some insight on its underlying structure of argumentation. The participants at this symposium showedmethatalthoughformallogicisimportantinidentifyingtheinferential structuresoflegalreasoning,therewerevastareasoflegalargumentationthat simplycriedoutforanalysesbythemorepracticalandcontextualcase-by-case methodsofinformallogic. IwouldliketothankKevinSaunders,RichardFriedman,JohnRogers,Rob- ert Rodes, Patricia Sayre, Larry Alexander, Howard Pospesel, and Layman Allen for their open-minded willingness to listen to a new and not widely ac- ceptedpointofview.Chapter5 isbasedontheinvitedlectureIgaveatNotre DameLawSchoolonNovember15,1997. Therevisedversionofthislecture waspublishedas‘‘APragmaticModelofLegalDisputation,’’NotreDameLaw Review 73 (1998): 711–35. Chapter 8 is based on parts (in revised form) of threepreviouslypublishedpapers.Onepaperwasoriginallyaninvitedkeynote lecturegivenattheInternationalConferenceonFormalandAppliedPractical Reasoning, FAPR ’96, in Bonn, Germany, in June 1996. The paper later ap- pearedinpublishedformas‘‘HowCanLogicBestBeAppliedtoArguments?,’’ LogicJournaloftheIGPL[InterestGrouponPureandAppliedLogic]5(1997): 603–14.Thesecondpaper,‘‘EthoticArgumentsandFallacies:TheCredibility Function in Multi-Agent Dialogue Systems,’’ was published in Pragmatics and ix ..........................9541$$ $ACK 07-24-0211:43:00 PS