Handling uncertainty in a Court of Law

• Jurisdiction: South Africa
• Date: 16 August 2019
• Published date: 16 August 2019
• Author: MA Muller
• Citation: (2012) 23 Stell LR 370
• Pages: 370-381

370

HANdLING uNCERTAINTY IN A COuRT Of

LAw

MA Muller

BSc MSc PhD

Senior Lecturer, University of Stellenbosch

1 Introduction

Many people have dif cult y handling uncertai nty because the very n ature

of u ncertainty ofte n runs counter t o our intuition. By our way of thi nking

we make errors of logic and our approach is generally wrong. The analysis

of uncertainty is not something that lies w ithin most people’s exper ience.

Courts are burdened wit h the task of considering dif ferent pieces of evidence,

often of different degrees of uncertainty. Eventually the court somehow has to

weigh up the different pieces of evidence and arrive at a conclusion. And there

are r ight ways and wrong ways of reasoni ng with uncer tainty. People make

mistakes when left to their own devices. When it happe ns in a court of law it

can be extremely prejudicial to the defend ant.1

Recently several cour t cases grappled with problems of u ncertainty and in

some instances came to conf using conclusions causing dismay in the forensic

scientic community.2 On 8 February 2011 leading forensic scientists

and statisticians issued a “position statement” which was prompted by a

controversial judgment in the British Court of Appeal in the case R v T.3

The rst point made i n the position statement reads as follows:

“The interpretation of scientic evidence invokes reasoning in the face of uncertainty. Probability

theory provides the only coherent logical foundation for such reasoning.” 4

The Board of the European Network of Forensic Science Institutes, which

is active in 33 countries, e ngaged itself to implement the principles outlined

in this position statement. It is feared that t he judgment i n R v T will be “u sed

as a weapon for defending the status quo or even a retu rn to pre-scientic

not ion s”.5

In this paper dif ferent manifestations of faulty reason ing concerning

uncertai nty are discussed. Each section starts with a simplied example which

1 P Donnelly “Appealing Stat istics” (2005) 2 Significance 46 47

2 CEH Berger, J Buckle ton, C Champod, IW Evet t & G J ackson “ Evidence Ev aluation: A Respo nse to

the Cour t of Appeal Judgme nt in R v T ” (2011) 51 Science & Ju stice 43-49; M Redmayn e, P Rober ts,

C A itken & G Jackson “Forensic Science Evidence in Qu estion” (2011) 5 Crim L Rev 347-356; B

Robertson , GA Vignaux & CEH Berger “Extendi ng the Confu sion about Bayes” (2011) 74 Mod L Rev

444- 455

3 R v T [2010] EWCA Crim 2 439

4 Public Statement by 36 Forensic Scient ists and Statisticia ns “Expressing Evaluat ive Opinions: A Position

Statement ” (2011) 51 Science & J ustice 1-2

5 Berger et al (2011) Science & Justice 49

(2012) 23 Stell LR 370

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