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  • Writer's pictureAmanda Gladin-Kramer

What are Expert Witnesses and Why Do I Need Them?

Surgeons in masks looking down in a circle. Expert witnesses in California personal injury law.

If your personal injury case goes to trial, there are several types of witnesses who may testify. Witnesses to a vehicle collision may describe what they saw happen. Friends and family of the injured victim may speak about their loved one’s pain and suffering and how their injury changed their life. These witnesses are called “lay witnesses.” Lay witnesses do not have particular training or expertise relevant to the legal case. The things that lay witnesses can testify about are limited. They cannot give opinions about many issues in the case.

For example, let’s say a construction worker slipped and fell at a drugstore in San Jose. There is a dispute about whether the man’s debilitating back pain was caused by his slip and fall or whether it is due to wear and tear from his job. The construction worker’s boss can testify that the construction worker went from doing his job without complaints before the slip and fall to barely being able to lift anything in the days after the slip and fall. He can describe what he saw and experienced. But the boss can’t give an opinion on the cause of the construction worker’s injury. The construction worker’s doctor CAN give an opinion on what caused the injury, based on their training and expertise, looking at x-rays or MRI images, doing a physical exam of the construction worker, or reviewing his medical history.

Expert witnesses are engineers, scientists, economists, and medical professionals, from chiropractors to radiologists to psychologists and orthopedic surgeons. If they qualify as an expert witness, they can use their “special knowledge, skill, experience, training, and education” to give opinions about the case under California Evidence Code § 801. Expert opinion can cover anything from whether a driver was negligent in an accident, whether a wheelchair ramp was built to code, or how fast a vehicle was traveling at the moment of impact. They can also testify about what medical treatment someone will need in the future or whether someone will be able to return to work after getting hurt.

Expert testimony is often necessary to prove things that may seem simple or obvious. If you are fighting in court to get your medical bills paid, you must prove to the jury that your injuries were caused by the accident and that the medical treatment you received was reasonable and necessary. How to prove this? In most cases, a doctor will need to testify about your injuries and the medical treatment you received. Under California law, you can’t just let the jury read your medical records or listen to you testify about your doctor visits as evidence. Your attorney will make closing arguments, but those arguments must be based on the evidence shown at trial.

Both the plaintiff (the injured person bringing the case) and the defendant (the person at fault, with their insurance company in control) can hire expert witnesses. The jury will listen to testimony from expert witnesses for both the plaintiff and defense and decide which is more credible. Expert witnesses are paid for their time. This is expensive. Your personal injury attorney must choose wisely about when to use an expert witness. Mercado Kramer LLP’s attorneys have worked with dozens of expert witnesses to prepare cases for trial.

One case involved a fatal collision between a truck owned by a large farming company and a sedan with multiple people inside. The people in the car had multiple, incredibly serious injuries requiring a lifetime of medical care. There were over 30 expert witnesses involved in the case. In that situation the case resulted in a settlement of eight figures – well worth the investment in expert witnesses.

Sometimes, your attorney will use an expert at the start of a case. Consider a wreck where a tractor-trailer and a passenger car crash on the center line of a dark road. The accident scene (the debris field, skid marks, and more) may contain crucial evidence that an accident reconstruction expert should examine immediately to help determine who is at fault.

Most cases do settle out of court without requiring expert witnesses. But when deciding whether to hire an attorney, you should use their experience using expert witnesses. Whether you suffered a slip and fall in Salinas or a car wreck in San Jose, you want your personal injury attorney to be ready for whatever comes.

This blog provides general information and is not legal advice. Call 888-311-4050 today for a free consultation with our California personal injury attorneys.   


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