The purpose of this study is to improve legal judgment of scientific evidence on the causality between hazardous chemical substances and damage. To this end, the issues involved in interpreting scientific evidence on causality in the court are critically reviewed, and the court judgment and the expert witness examination records in the humidifier disinfectant case are analyzed.

Chapter 2 examines legal theories of causality and its proof. This chapter provides an overview of the significance of causality in the criminal law, the legal theories of causality, and objective attribution theory. In addition, regarding the proof of causality in criminal trials, we review the principles of trial by evidence and strict proof in terms of fact finding and examine the degree of proof in terms of causality when the causality is required to satisfy the criteria of strict proof.

Chapter 3 examines scientific evidence submitted to prove causality in the court. First, in order to understand the significance of scientific evidence, we review the concept of evidence under the Criminal Procedure Act and the concept and types of scientific evidence. Also, we examine legal discussions on the finding of causality through indirect evidence as scientific evidence can be considered indirect evience. In addition, this chapter examines the preassumptions involved in producing various types of scientific evidence submitted to prove the causality between exposure to hazardous chemicals and damage. To this end, we overview the basic frameworks for toxicological research, epidemiological research, and medical diagnosis. Also, we briefly discuss what was at issue in the court case on humidifier disinfectants in terms of the production of scientific evidence. Finally, this chapter examines the contents of the criteria for the US case law on the admissibility of scientific evidence and their implications for domestic law. 

Chapter 4 examines the method of determining the causality between exposure to hazardous chemicals and damage, focusing on epidemiological research. To this end, we examine the ways in which science understands causality and the legal principles for determining causality between exposure to hazardous chemicals and damage in compensation cases and criminal cases, respectively. In addition, this chapter provides an overview of the Hill standard, which is the standard for general causal inference, and the standard for inferring specific causal relations from epidemiological studies. 

Chapter 5 and Chapter 6 analyze the court case regarding humidifier disinfectant containing CMIT/MIT. Chapter 5 provides a quantitative analysis of the witness examination records of about 3,100 pages and the written judgment of about 130 pages (core word frequency, core word relationship, and topic modeling), through which the intrinsic semantic structure of the texts is analyzed. Drawing upon the results of the analysis, we identify the issues that the prosecution, the defendant, and the court focused on over the proof of causality. Chapter 6 identifies the areas of contention with regard to scientific evidence submitted to the court (exposure assessments, risk assessments, animal and cytotoxicity tests, and epidemiological studies) by analyzing the witness examination records and the judgment. 

Chapter 7 summarizes the problems shown by the court in determining the probative power of various scientific evidence in terms of proving the causality between exposure to humidifier disinfectant containing CMIT/MIT and damage. This chapter also offers possible cuases of the problems shown by the court and suggestions for improving court judgment.