Argument assistance software in legal reasoning

185 Pages·2012·9.89 MB·Dutch

Argument assistance software in legal
reasoning
Formalizing Toulmin’s model for arguing

Degree programme: Open University of the Netherlands, Faculty of Management, Science &
Technology
Business Process Management & IT master's programme

Course: IM9806 Business Process Management and IT Graduation Assignment

Student: Elleke Baecke
Identification number: 851738529
Date: March 7 2018
Thesis supervisor Prof. dr. ir. Stef (S.M.M.) Joosten
Second reader Dr. Lloyd (L.W.) Rutledge
Version number: 1
Status: final version

Abstract in Dutch

Een jurist gebruik argumenten om de rechter te overtuigen van het standpunt van zijn cliënt. Om de
rechter te overtuigen, gebruiken juristen legal reasoning modellen – al dan niet bewust. Om hen te
helpen zich meer bewust te worden van de argumentatie structuren die ze gebruiken, heb ik in deze
afstudeerscriptie een prototype voor een informatiesysteem ontwikkeld. Het doel van het prototype
is om professionals te ondersteunen bij legal reasoning en niet om de argumentatie te
automatiseren. Door het gebruik van het prototype krijgt de jurist een beter inzicht in de
argumentatie die hij kan gebruiken in een zaak. Dit kan helpen bij het analyseren van de zaak door
de strenge en zwakke punten in de argumentatie – én die van de tegenpartij – te bepalen en ervoor
te zorgen dat geen elementen in de argumentatie vergeten worden.

Het prototype is ontwikkeld met de Ampersand tool door Toulmins theorie over argumentatie te
analyseren. Toulmins model is aangepast aan de formele logica van Ampersand. Het prototype is
gevalideerd en verbeterd door middel van het toepassen van echte uitspraken in rechtszaken en het
interviewen van juridische professionals.

Keywords
Legal reasoning, formal logic, information system, ampersand, Toulmin

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Abstract in English

Lawyers use arguments to convince the judge of their client’s position. In doing so, they apply legal
reasoning models – whether knowingly or unknowingly. To assist them in being more aware of the
argument structures they use, I have developed a prototype for an information system in this thesis.
The prototype aims to assist professionals with legal reasoning, and not to automate argumentation.
By applying the prototype, the lawyer will have a better insight in the argumentation he can use in a
particular case. This can help analyze the case by determining the strong and weak points in the
argumentation – and the argumentation used by the opposing party – as well as making sure no
elements of the argumentation are left out.

The prototype was developed with the Ampersand tool by analyzing Toulmin’s leading theory on
argumentation. His model has been adapted to fit the formal logic of Ampersand. The prototype was
validated and further improved by applying real life test cases and interviewing legal professionals.

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Index

Abstract in Dutch ...................................................................................................................................... i
Abstract in English ................................................................................................................................... ii
Index ....................................................................................................................................................... iii
1. Introduction .................................................................................................................................... 1
1.1. Thesis structure ....................................................................................................................... 1
2. Theoretical framework ................................................................................................................... 2
2.1. Problem analysis ..................................................................................................................... 2
2.1.1. Information systems ....................................................................................................... 2
2.1.2. Argumentation ................................................................................................................ 3
2.1.3. Limitation of the scope ................................................................................................... 4
2.2. Formulating research questions ............................................................................................. 4
2.3. Relevance ................................................................................................................................ 5
2.4. Results and conclusions .......................................................................................................... 5
2.4.1. Argumentation scheme of Toulmin ................................................................................ 6
2.4.2. The ArguMed system ...................................................................................................... 7
2.4.3. Ampersand ...................................................................................................................... 8
2.4.4. Formalizing theories Toulmin and ArguMed ................................................................ 11
2.4.5. Further refinements ...................................................................................................... 12
2.4.6. Conclusions of theoretical framework .......................................................................... 13
3. Methodology ................................................................................................................................. 15
3.1. Research method .................................................................................................................. 15
3.2. Data collection and analysis .................................................................................................. 15
3.3. Validity .................................................................................................................................. 16
4. Results ........................................................................................................................................... 18
4.1. Concepts, relations and population ...................................................................................... 18
4.1.1. The sample case ............................................................................................................ 18
4.1.2. Scope, Argument, Claim, Justification, Datum, Warrant, Backing ................................ 19
4.1.3. Rebuttal ......................................................................................................................... 21
4.1.4. Validation ...................................................................................................................... 22
4.1.5. Sub................................................................................................................................. 26
4.1.6. Cumulation .................................................................................................................... 28
4.1.7. String ............................................................................................................................. 29
4.2. Interface ................................................................................................................................ 29
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5. Conclusion, discussion and recommendations, reflection ........................................................... 35
5.1. Discussion .............................................................................................................................. 35
5.1.1. Basic model ................................................................................................................... 35
5.1.2. Addition of relation “sub” ............................................................................................. 35
5.1.3. Nominalization of concepts Warrant and Rebuttal ...................................................... 37
5.1.4. Addition of validation .................................................................................................... 40
5.1.5. Addition of cumulation ................................................................................................. 42
5.1.6. Rebuttal ......................................................................................................................... 43
5.1.7. Final validation of the model ........................................................................................ 44
5.2. Conclusions ........................................................................................................................... 44
5.3. Recommendations for further research ............................................................................... 45
5.4. Reflection .............................................................................................................................. 46
Acknowledgements ............................................................................................................................... 48
References ............................................................................................................................................. 49
Addenda ................................................................................................................................................ 51

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1. Introduction

This thesis aims to help legal professionals with software for legal argumentation. Truth in the legal
profession relies on human decisions rather than mathematical logic. It is commonly accepted that
reasoning by legal professionals is defeasible.1 I will try to develop a software system for legal
argumentation, using mathematics to build software and defeasible reasoning to construct legal
arguments.

Thus, this thesis has examined the feasibility of developing an information system that will support
lawyers when constructing a valid argument. In developing this prototype, the Ampersand method
and tool has been used. In Ampersand, formal logic serves as a basis for information systems.

1.1. Thesis structure

First, the theoretical framework will be presented. I have analyzed the problem by investigating
what research has been done so far. After that, I have formulated my research question as well as
sub questions that have been investigated in the literature study. I have concluded with answering
these sub questions and drawing conclusions. The results of this literature study, are presented in
chapter two of this report.

After setting the theoretical framework, I have formulated my research strategy in chapter 3. It
describes how I planned to collect and analyze my data and it discusses the validity of my methods.

In chapter 4 the results of the empirical part of the research are presented. This is done by showing a
sample case that I have used to build and test my prototype.

Finally, in chapter 5 the outcomes are discussed by explaining how the prototype was developed and
discussing more sample cases. Also, conclusions are drawn and recommendations for further
research are made.

1 Prakken H. & Sartor G. (1996). A Dialectical Model of Assessing Conflicting Arguments in Legal Reasoning.
Artificial Intelligence and Law (Volume 4, Issue 3-4, pp 331–368), p. 3.
2. Theoretical framework

2.1. Problem analysis

This research focuses on information systems that involve legal reasoning. Before formulating
research questions, I have investigated what is known about the subject. I have investigated
documentation on information systems on the one hand, and looked into argumentation theories on
the other hand.

2.1.1. Information systems

A first aspect that needed further investigation, is distinguishing the various types of information
systems that have been released and which omissions have been found in those systems. Amongst
others, Prakken2 as well as Verheij and Hage3 have researched legal informatics.

Verheij and Hage notice that systems that involve legal informatics tend to emphasize on looking up
textual information and saving knowledge. Such systems are similar to systems that Prakken calls
deductive knowledge systems. These are systems that present legal knowledge as simple if-then-
rules that are being applied to the facts of specific cases by a computer. Even though these systems
are simplified, they have been used most widely in practice. For example, they support officials
trying to manage complex structures of regulations. According to Prakken these systems are mainly
suitable when modeling regulations and not for legal reasoning as such.

Systems that enable a computer to make a legal judgement in specific cases, are being referred to as
argumentation based knowledge systems by Prakken. Even though a few examples can be found in
practice (e.g. the EMS-system for Dutch environmental permit law), Prakken concludes that for now
it shows to be too difficult to use these systems in practice.4 It appears that many circumstances of a
specific case are not foreseen. In addition to that – practical objections put aside – one could also
raise the question whether or not a judgement made by a computer would jeopardize justice of a
decision.

I follow Prakken in his opinion that legal reasoning is a creative process, which is therefore difficult
for computers to execute.

The last category of systems that Prakken distinguishes, is the category of argumentation
management systems. According to Prakken this is software that can be used to develop a digital
case file, that structures documents in terms of argumentation. Prakken explicitly notes that such
systems are meant to support lawyers and not to automate argumentation.
Research on argumentation systems has mainly focused on visualization of argumentation so far.

Argumentation systems show to be interesting because of the possibilities related to artificial
intelligence. Even though this has not been part of the scope of this research, it might be valuable
for future research.

2 Prakken, H. (2005). Argumentatiemanagement voor juristen. Groningen: Henry Prakken.
3 Verheij, B., & Hage, J. C. (2002). Rechtsinformatica als tak van wetenschap. In A. Oskamp, & A. R. Lodder
(Eds.), Informatietechnologie voor Juristen. (2 ed., pp. 69-91). (Reeks informatica en recht; Vol. 20). Deventer:
Kluwer.
4 Prakken, H. (2005). Argumentatiemanagement voor juristen. Groningen: Henry Prakken, p. 6
2
Verheij also explicitly distinguishes supporting systems (which he calls assistance systems) from
automated systems (which he calls automated reasoning systems).5 One of the differences between
supporting systems and automated systems, is that the first category is more passive. Furthermore,
known problems with the complexity of law can be overcome by using supporting systems. The open
and dynamic nature of law causes problems when developing automated systems.

It is clear that Prakken as well as Verheij and Hage think that legal IT systems should support
lawyers, and not replace work being done by lawyers. I share that opinion. Disregarding the
technical (in)feasibility of developing computer systems that can replace lawyers, I am convinced
that this would not be desirable. A legal decision should be taken by humans, that can do justice to
all circumstances at stake. By supporting legal argumentation, it is possible to let the user decide
about truth. This is consistent with the subjective truth principle in legal argumentation.

Therefore, my research has focused on systems that support users in the process of legal reasoning,
and not automate argumentation. For practical reasons have limited the scope of this research to
the Dutch legal system.

I have looked more specifically into Argumed, developed by aforementioned Verheij, because it is an
example of an argument support system. It does not try to automate legal argumentation.” Verheij
explains his system in i.a. his article “Automated argument assistance for lawyers”.6 Verheij’s
ArguMed will be further explained in paragraph 2.4.2.

The ArguMed system shows a visual presentation of the argumentation and thus has an informal
nature. Formal logic has a “black or white character”; a statement is either true or false. In a legal
case, a judge has to make a “black or white decision” as well; he will either accept or decline the
claim. Furthermore, lawyers that are looking for support in constructing their argumentation, will
also feel the need to get a clear answer on whether or not their argumentation is valid or not. To
achieve this, there is a need for a formal nature.

2.1.2. Argumentation

Now that we have examined existing information systems, our attention shifts to the qualities of a
good reasoning structure that can serve as a basis for an information system. Various articles about
information systems regarding legal reasoning refer to Stephen Toulmin’s theory.7 This theory is still
relevant and widely applied in many disciplines.

5 Verheij, B. (2003). Artificial argument assistants for defeasible argumentation. Artificial Intelligence 150 (1-2),
291-324.
6 Verheij, B. (1999). Automated argument assistance for lawyers (abstract). BNAIC '99. Proceedings of the
Eleventh Netherlands/Belgium Artificial Intelligence Conference (eds. Postma, E., & Gyssens, M.), 269-270.
Maastricht.
7 i.a.:
Verheij, B., & Hage, J. C. (2002). Rechtsinformatica als tak van wetenschap. In A. Oskamp, & A. R. Lodder (Eds.),
Informatietechnologie voor Juristen. (2 ed., pp. 69-91). (Reeks informatica en recht; Vol. 20). Deventer: Kluwer;
van den Braak, S.W. (2010): Sense-making software for crime analysis. Enschede: Susan van den Braak;
Verheij, B. (2001). Anchored Narratives and Dialectical Argumentation. ICAIL-2001 Workshop on AI and Legal
Evidence;
Verheij, B. (1999). Automated argument assistance for lawyers (abstract). BNAIC '99. Proceedings of the
Eleventh Netherlands/Belgium Artificial Intelligence Conference (eds. Postma, E., & Gyssens, M.), 269-270.
Maastricht;
Bex, F. & Reed, C. (2011). Schemes of Inference, Conflict, and Preference in a Computational Model of
Argument. Studies in Logic, Grammar and Rhetoric, 23 (36), pp39-58.

3
Toulmin uses “argument maps” to visualize arguments. In 1958, he published the book “The uses of
Argument”, in which he explains his theory. New in his theory was the introduction of the “warrant”.
Earlier theories only distinguished “reason” and “conclusion” and led to validation based on just
these two elements. Toulmin introduced the warrant to connect these two elements that made sure
the step between reason and conclusion could be evaluated.8 Toulmin’s theory will be further
explained in paragraph 2.4.1.

Toulmin’s theory shows several similarities with Verheij’s ArguMed. The similarities and differences
will be briefly discussed in paragraph 2.4.6.

2.1.3. Limitation of the scope

Due to the limited scope of the research, various interesting sources that have been studied (e.g.
regarding to deduction) have not been included in the research.

This study limits legal reasoning by excluding the psychological processes that judges experience
when making a decision. Wahlgren9 calls this “legal reasoning in the narrow sense”. This elimination
is motivated by the nature of the research group, which is in computer science and lacks any
psychological expertise.

Apart from the distinction between legal reasoning in a narrow and in a broad sense, there is a
difference between reasoning with rules and reasoning with cases. This distinction shows parallels
with the difference between law systems that focus on the law (e.g. the Netherlands), and law
systems that are based on case law (e.g. the United States).10 Since the Netherlands have a law
system that focusses on law, it might be assumed that this research will be limited to reasoning with
rules. However, this would not do justice to the relevance of the research. Rules never stand alone
and are not rigid; they need to be interpreted by case law – also in law focused law systems such as
the Dutch law system. If the research would be limited to reasoning with rules, the research would
have no practical relevance.

2.2. Formulating research questions

In the previous paragraph we have analyzed the problem. On that basis, I have formulated research
questions, which are presented in this paragraph.

This research explores formal models for legal reasoning. For this purpose, I have formalized
theories of legal reasoning and applied these theories in software prototypes. I have explored
whether or not such a formal model can be developed. In order to do so, I have examined in which
ways theories about legal reasoning can be formalized, using formal logic and Ampersand. This will
contribute to a better understanding of legal reasoning structures.

I have also validated the developed model by applying real life examples.

8 Reed, C., Walton, D., & Macagno, F. (March 2007). Argument diagramming in logic, law and artificial
intelligence. The Knowledge Engineering Review, 22 (1), 1-22.
9 Wahlgren, P. (1992). Automation of legal reasoning: A Study on Artificial Intelligence and Law.
10 Verheij, B., & Hage, J. C. (2002). Rechtsinformatica als tak van wetenschap. In A. Oskamp, & A. R. Lodder
(Eds.), Informatietechnologie voor Juristen. (2 ed., pp. 69-91). (Reeks informatica en recht; Vol. 20). Deventer:
Kluwer.
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