Dateline: January, 2007, Issue 3

How does testimony comparing the death risk from asbestos exposure to other death risks affect verdicts?

The increased lifetime risk of death from asbestos exposure for particular air concentrations is a calculable quantity, and is often considerably less than the risk of death from other substances such as smoking, saccharin in soft drinks, chest X-rays, aflatoxin in peanut butter, and radiation from living in a brick house.

Two studies conducted 12 years apart by different researchers - Slovic et al. (1990) and Johnson (2002) - reached similar findings on the value of a defendant offering such risk comparison information in an asbestos trial.

In this research, all jurors learned, without dispute, that the plaintiffs had an increased lifetime risk of death of .23 per million from exposure to asbestos. Many jurors also received a table showing this death rate from asbestos exposure compared to death rates from smoking (88,000), saccharin in soft drinks (170), chest X rays (41), aflatoxin in peanut butter (11), and radiation from living in a brick house (4), accompanied by an expert witness who explained and interpreted the table on behalf of the defendant. Some jurors also were provided a criticism of the risk comparison table by a plaintiff expert. And some of these jurors additionally heard the defendant's expert "pre-deny" the criticisms of the plaintiff's expert.

Jurors exposed only to the defense risk comparison table (and not the plaintiff expert's criticisms) found the defendant liable less often than jurors not receiving the risk comparison information. However, jurors who received criticism of the risk comparison by a plaintiff expert judged the defendant as or more liable than jurors receiving no risk comparison information. Jurors who heard the defendant expert "pre-deny" the criticisms the plaintiff expert later gave also found the defendant liable less often than jurors not receiving the risk comparison information. The researchers concluded that risk comparison information can influence verdicts, and that "pre-denial" (technically called "inoculation") is necessary for maintaining the persuasiveness of the risk comparison information in the face of plaintiff criticism.

The researchers also found that in an asbestos trial the risk comparison, critique and pre-denial information was of less importance than jurors' own background and attitudes. Some jurors were simply more likely to hold the defendant responsible than other jurors, independent of risk comparison information. Jurors most likely to hold the defendant responsible were female, less educated, poorer, renters, minorities, more likely to speak a language other than English at home, interested in asbestos as a public health issue, and especially likely to assume that any exposure to a carcinogen would lead to cancer.

Source Slovic, P., Kraus, N., & Covello, V. T. (1990). What should we know about making risk comparisons? Risk Analysis, 10, pp. 389-392.

Source Johnson, B.B. (2002). Stability and inoculation of risk comparisons' effects under conflict: Replicating and extending the “asbestos jury” study by Slovic et al. Risk Analysis, 22, pp. 777-788.