These cases may benefit from the presence of an expert witness who can focus on the question of liability. In particularly complex cases, it may be prudent to hire multiple experts—one to focus on causation, and another to focus on liability.
Causation vs. Liability
Causation and liability are closely linked, but they are two separate questions. Causation focuses on how a personal injury came to occur. Liability focuses on who was responsible for the injury. As a result, causation concerns itself with both cause in fact—the but-for cause of an injury—and proximate cause—the foreseeability that a particular action would cause this type of harm. Liability arguments concern themselves primarily with proximate cause.
For instance, suppose that a children’s toy contains unacceptably high levels of lead. It was introduced during the manufacturing process and sold with no warnings or notice as to the lead content. A parent brings a claim after their child suffers symptoms consistent with lead poisoning. Many but-for causes exist here. If not for the lead in the toy, the child would not have suffered lead poisoning, but the same can be said for the parent’s decision to purchase the toy, the parent’s decision not to test the toy for lead, or the child’s habit of chewing on the toy.
To establish liability, the attorney for the parent and child would need to establish not only that the lead used in the toy caused the harm, but that the manufacturer could have foreseen this outcome. The attorney could also try to establish that the manufacturer had a duty to avoid using lead in its products—though this depends on the presence of an applicable law or mandate that forbade the use of lead in children’s toys.
In this situation, an expert who can discuss the mechanisms by which lead entered the child’s body and caused injury is likely to have a different background from an expert who can discuss manufacturing standards for children’s toys. The former expert is best for focusing on but-for causation, while the latter can most profitably focus on proximate causation.
Meeting Specialized Standards of Liability
In some personal injury claims, establishing both cause in fact and proximate cause is still insufficient to establish liability on the part of the defendant. Medical malpractice claims, for example, require a demonstration that the defendant’s actions were not only the but-for and foreseeable cause of the plaintiff’s injury, but also that they deviated from the established standard of care.
Imagine a medical malpractice claim in which a neurosurgeon allegedly caused injury to a patient during brain surgery. Here, a neurologist’s expert testimony may be valuable in establishing causation. The neurology expert may be able to explain that but for the neurosurgeon’s decision, the harm would not have occurred, and that the decision occurred at a critical moment that made the harm highly foreseeable.
But did the defendant neurosurgeon’s decision fall below the standard of care? The neurologist who can explain how the injury occurred may not be equipped to discuss that decision in the context of neurosurgery best practices. Here, another neurosurgeon or similar expert may be needed to connect the dots between causation—the neurosurgeon’s decision caused the injury—and liability—that the decision deviated from the standard of care.
Litigators may also find themselves facing a case where causation is clear, but liability is not. In the previous example, the causation expert may determine that the defendant neurosurgeon’s action caused the harm, but the liability expert may opine that the neurosurgeon adhered to the standard of care. The expert could argue that making any other decision in that moment would have caused even greater harm—even death. Here, the liability expert might help establish that an ordinarily prudent neurosurgeon in the same situation would have made the same decision, even though the patient suffered injury as a result.
Using Experts to Clarify Questions of Liability
In some cases, one party will use causation to obscure questions of liability. In several tobacco industry cases, for example, expert witnesses argued that but-for causation couldn’t be established to connect any one individual’s lung cancer, because there was no control group. In other words, since we don’t know that this person wouldn’t have gotten lung cancer anyway, we can’t hold tobacco companies liable for that injury.
This argument focuses on but-for cause, obscuring a key liability question: was the harm foreseeable? In the case of tobacco industry litigation, plaintiffs began to make headway when they harnessed experts’ ability to focus on what the tobacco industry knew about the links between smoking and lung cancer. This focus on liability allowed plaintiffs’ experts to contextualize the defendants’ causation arguments and, ultimately, to prevail.
Complex cases give rise to complex issues, which require careful planning and strategy to address. Often, choosing an expert who can focus on causation and another expert who can focus on liability will help clarify complicated issues for the fact-finder, improving the chances of a favorable result.