Epidemiology is the study of patterns of health and illness and associated factors at the population level. Forensic (applying science to answer questions of interest to a legal system) epidemiology can be useful in personal injuries cases to prove causation of an injury.
The personal injury claimant has the burden of proving that his/her injuries or conditions were more likely than not caused by an accident or offending agent (e.g., smoking). This burden becomes more difficult when the complained of injuries and conditions can occur naturally without a known precipitating cause. Examples include herniated intervertrebral discs and lung cancer.
Various types of experts, including doctors and biomechanists, are used on both sides to present evidence regarding the issue of causation. The expertise of forensic epidemiologists is greatly underutilized.
Epidemiologists use “relative risk” to compare the chance of injuries and conditions being caused in certain ways. Two examples: (1) The risk of an intervertebral disc injury from a crash is 1 in 200, while the risk of an individual developing the symptoms at the same point in time if the crash hadn’t occurred is usually less than 1 in 100,000. (2) The chance that a person who smokes will get lung cancer is 20% compared to 1% for non-smokers.
A common defense tactic in civil justice cases is to propose alternative explanations for the injuries/conditions besides the targeted accident or exposure. The defendant’s hope is that a jury will attribute the damage to something other than the accident or exposure. The epidemiologist can be an important expert to counter the shifting-blame defense.
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