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Sannolikhetsteori i domstolen? - En utredning av för- och nackdelarna med den Bayesianska bevisvärderingsmetoden

Bellander, Axel LU (2021) JURM02 20212
Department of Law
Faculty of Law
Abstract (Swedish)
I svensk rätt gäller principen om fri bevisprövning. Principen innebär att domstolen fritt ska värdera den bevisning som presenteras under en rättegång. Det saknas i princip lagstadgade regler för hur bevisvärderingen ska utföras. I rättspraxis och lagförarbeten har dock vissa bevisvärderingsprinciper utvecklats. Dessa principer föreskriver bland annat att domstolen ska utföra bevisvärderingen rationellt, objektivt, och strukturerat. Samtidigt saknas det tydliga riktlinjer för hur domstolen ska utföra bevisvärderingen i enlighet med dessa principer.

Den Bayesianska sannolikhetsteorin är en av de ledande internationella bevisvärderingsmetoderna. Förespråkarna menar, att om bevisvärderingen utfördes i enlighet med denna metod, skulle... (More)
I svensk rätt gäller principen om fri bevisprövning. Principen innebär att domstolen fritt ska värdera den bevisning som presenteras under en rättegång. Det saknas i princip lagstadgade regler för hur bevisvärderingen ska utföras. I rättspraxis och lagförarbeten har dock vissa bevisvärderingsprinciper utvecklats. Dessa principer föreskriver bland annat att domstolen ska utföra bevisvärderingen rationellt, objektivt, och strukturerat. Samtidigt saknas det tydliga riktlinjer för hur domstolen ska utföra bevisvärderingen i enlighet med dessa principer.

Den Bayesianska sannolikhetsteorin är en av de ledande internationella bevisvärderingsmetoderna. Förespråkarna menar, att om bevisvärderingen utfördes i enlighet med denna metod, skulle bevisvärderingen bli mer rationell, strukturerad, och transparent.

Syftet med uppsatsen är att utreda vilka för- och nackdelar som finns med att utföra bevisvärderingen i enlighet med den Bayesianska sannolikhetsteorin. För att uppnå syftet redogör uppsatsen först för vad bevisvärdering är och hur det regleras i svensk rätt. Sedan redogör uppsatsen för den Bayesianska sannolikhetsteorin, genom att utreda vad sannolikhetsteori är, och förklara några grundläggande matematiska sannolikhetsregler. Uppsatsen visar även hur Bayes teorem kan härledas. Vidare redogörs för olika teorier om hur sannolikheter ska definieras. En av dessa är teorin om subjektiva sannolikheter som den Bayesianska sannolikhetsteorin är baserad på. Sedan redogör uppsatsen för Bayes teorem och visar hur det kan användas. Vidare redogörs för några grundläggande utgångspositioner för och emot den Bayesianska sannolikhetsteorin.

Uppsatsen presenterar sedan ett antal centrala argument för den Bayesianska sannolikhetsteorin, och ett antal centrala problem med teorin. Argumenten och problemen analyseras mot bakgrund av uppsatsens syfte. Sist följer en avslutande diskussion där uppsatsens frågeställning besvaras. Uppsatsens slutsats är att fördelarna med den Bayesianska sannolikhetsteorin överväger nackdelarna, och att bevisvärderingen därför borde utföras i enlighet med den Bayesianska sannolikhetsteorin. (Less)
Abstract
In Swedish law, the principle of free sifting of evidence applies. The principle means that the court freely should evaluate the evidence that is presented during a trial. In principle, there are no statutory rules that governs how the evaluation of evidence is to be carried out. However, in case law and in the legislative history some principles of evidence evaluation have emerged. These principles prescribe, among other things, that the court should carry out the evaluation of evidence rationally, objectively, and in a structured manner. At the same time, there are no clear guidelines for how the court should carry out the evaluation of evidence in accordance with these principles.

The Bayesian theory of probability is one of the... (More)
In Swedish law, the principle of free sifting of evidence applies. The principle means that the court freely should evaluate the evidence that is presented during a trial. In principle, there are no statutory rules that governs how the evaluation of evidence is to be carried out. However, in case law and in the legislative history some principles of evidence evaluation have emerged. These principles prescribe, among other things, that the court should carry out the evaluation of evidence rationally, objectively, and in a structured manner. At the same time, there are no clear guidelines for how the court should carry out the evaluation of evidence in accordance with these principles.

The Bayesian theory of probability is one of the leading international methods of evidence evaluation. The proponents believe that if the evaluation of evidence was carried out in accordance with this method, the evaluation of evidence would become more rational, structured, and transparent.

The purpose of this essay is to investigate the advantages and disadvantages of performing the evaluation of evidence in accordance with the Bayesian theory of probability. To achieve the purpose, the essay first accounts for what evaluation of evidence is and how it is regulated in Swedish law. Then the essay accounts for the Bayesian theory of probability, by investigating what probability theory is, and explaining some basic mathematical rules of probability. The essay also shows how Bayes theorem can be deduced. Furthermore, some theories on how probabilities should be defined are accounted for. One of these is the theory of subjective probabilities, which the Bayesian theory of probability is based upon. Then the essay accounts for Bayes theorem and displays how it can be used. Furthermore, some fundamental views for and against the Bayesian theory of probability are presented.

The essay then presents some central arguments for the Bayesian theory of probability, and some central problems with the theory. The arguments and the problems are analysed in accordance with the purpose of the essay. Lastly, a concluding discussion follows where the question of the essay is answered. The essay concludes that the advantages of the Bayesian theory of probability outweighs the disadvantages, and that the evaluation of evidence therefore should be carried out in accordance with the Bayesian theory of probability. (Less)
Please use this url to cite or link to this publication:
author
Bellander, Axel LU
supervisor
organization
alternative title
Probability theory in court?
course
JURM02 20212
year
type
H3 - Professional qualifications (4 Years - )
subject
keywords
straffrätt, rättsvetenskap, bevisvärdering, sannolikhetsteori, Bayesiansk sannolikhetsteori
language
Swedish
id
9069005
date added to LUP
2022-01-25 11:33:07
date last changed
2022-01-25 11:33:07
@misc{9069005,
  abstract     = {{In Swedish law, the principle of free sifting of evidence applies. The principle means that the court freely should evaluate the evidence that is presented during a trial. In principle, there are no statutory rules that governs how the evaluation of evidence is to be carried out. However, in case law and in the legislative history some principles of evidence evaluation have emerged. These principles prescribe, among other things, that the court should carry out the evaluation of evidence rationally, objectively, and in a structured manner. At the same time, there are no clear guidelines for how the court should carry out the evaluation of evidence in accordance with these principles. 

The Bayesian theory of probability is one of the leading international methods of evidence evaluation. The proponents believe that if the evaluation of evidence was carried out in accordance with this method, the evaluation of evidence would become more rational, structured, and transparent. 

The purpose of this essay is to investigate the advantages and disadvantages of performing the evaluation of evidence in accordance with the Bayesian theory of probability. To achieve the purpose, the essay first accounts for what evaluation of evidence is and how it is regulated in Swedish law. Then the essay accounts for the Bayesian theory of probability, by investigating what probability theory is, and explaining some basic mathematical rules of probability. The essay also shows how Bayes theorem can be deduced. Furthermore, some theories on how probabilities should be defined are accounted for. One of these is the theory of subjective probabilities, which the Bayesian theory of probability is based upon. Then the essay accounts for Bayes theorem and displays how it can be used. Furthermore, some fundamental views for and against the Bayesian theory of probability are presented. 

The essay then presents some central arguments for the Bayesian theory of probability, and some central problems with the theory. The arguments and the problems are analysed in accordance with the purpose of the essay. Lastly, a concluding discussion follows where the question of the essay is answered. The essay concludes that the advantages of the Bayesian theory of probability outweighs the disadvantages, and that the evaluation of evidence therefore should be carried out in accordance with the Bayesian theory of probability.}},
  author       = {{Bellander, Axel}},
  language     = {{swe}},
  note         = {{Student Paper}},
  title        = {{Sannolikhetsteori i domstolen? - En utredning av för- och nackdelarna med den Bayesianska bevisvärderingsmetoden}},
  year         = {{2021}},
}