Law 101 for Experts: Understanding the Different Phases of a Lawsuit

As an expert witness or consultant, you advise attorneys on technical issues in their cases and present your findings and analysis of these issues to a jury in the courtroom. 

Carolyn Casey, J.D.

Written by
— Updated on May 18, 2022

Law 101 for Experts: Understanding the Different Phases of a Lawsuit

As you perform your role, it’s good to have a basic understanding of the different phases of a lawsuit. Insights into the legal process and procedures will help you see your role in the larger context of a lawsuit. Understanding the process equips you to enhance your expert witness participation and performance.

Complaints and Answers

A lawsuit—a dispute between persons that the legal system will resolve—begins with the filing of a complaint. A plaintiff lays out their claims against the defendant in a complaint. The complaint details how the defendant’s actions caused personal or financial injury to the plaintiff. The party bringing a civil lawsuit will seek specific remedies from the court. Specific remedies can include financial payments or a court order for the defendant to do or stop doing something.

You’ll also hear about or review documents called a pleading. In most cases, the pleading is in the complaint. It’s the plaintiff’s description of what happened. Additionally, it’s also the legal argument for why the defendant is responsible for the plaintiff’s injuries.

Defendants are then required to file a response to a complaint called the answer. The defendants must file this document with the court by a specific date after a complaint. An answer contains the defendant’s position on the plaintiff’s claims. In some cases, a defendant’s counsel may seek advice on a medical standard of care or other technical issues. Doing so helps the lawyer develop their arguments for an answer that they are not liable for a plaintiff’s claims.

You will need to be very responsive to an attorney’s requests for your consultation as they are under a deadline. Failure to answer timely can result in a default judgment against their client. This means the client cannot argue their case, and the court simply orders them to pay the plaintiff’s damages.

Affirmative Defenses

Defendants may assert an affirmative defense. The defendants provide evidence that they should not be held liable even when they may have committed the alleged acts. In tort law, an example of an affirmative defense is a necessity. This defense argues that the conduct was necessary to avoid greater harm. In criminal law, claiming insanity is an affirmative defense.

In a car accident case, for example, an attorney may ask an expert to testify that—based on the expert’s reconstruction and analysis of the accident—if the defendant had not swerved into the plaintiff’s car, a child in the road likely would have died.

A Motion to Dismiss

Defendants may file a motion to dismiss. In such motions, the litigant may argue that a judge must dismiss a case because the court does not have authority to hear this type of case or that the plaintiff failed to state a claim for which the court can grant relief. There are several other bases for motions to dismiss, essentially saying a legal technicality was not observed.

Summary Judgment

An attorney may have hired you to assist in a case. However, the case may go away before an attorney needs your services under a summary judgment. Defendants or plaintiffs often file a motion for summary judgment. The party filing summary judgment is asking the court to enter a judgment in their favor without a trial. The party filing the motion must show that there is no genuine dispute on the material facts of the case. They must also convince a judge that they are entitled to a judgment as a matter of law.


The legal system provides for the parties to gather information from each other or third parties during discovery. In this phase, parties ask the other side to provide them with relevant documents in a request for production. Parties may also ask each other to complete written questionnaires known as interrogatories.

The most salient discovery procedure for you as an expert is the deposition. The other side may depose you. During this, the opposition asks questions about your background and your findings on the technical subject matter in the case. The opposing counsel frequently uses expert depositions in court to try to discredit an expert and their findings.


The bottom line in a lawsuit is the plaintiff wants a remedy from the court for the wrong they suffered. One remedy, of course, is monetary damages. Plaintiffs want the court to order the defendant to pay them a sum of money to compensate them for their injuries, pain and suffering, or losses. A restitution remedy involves the defendant taking an action to restore the plaintiff’s situation to what it was before the wrong. A court may also order a party to refrain from doing a certain act that is harming a plaintiff. Sometimes, you’ll also see a court not award any damages. This is called declaratory relief.

Attorneys often involve experts in the remedy phase of a lawsuit. Attorneys may need experts to calculate lost wages incurred during a medical leave following a car accident or unsuccessful surgery. Or an attorney may need a construction expert’s opinion to ascertain the costs of rebuilding after a construction defect, which the defendant must remedy.


In both state and federal systems, there are lower courts, appellate courts, and a supreme court. Litigants may file an appeal to the next level court arguing that a lower court judge made an error of law in their case. They ask the higher court to overturn the ruling and send it back to the lower court for another go at correctly applying the law.

An appeal of interest to experts is a challenge to a judge’s determination to exclude an expert’s testimony from a trial. When one side files a motion to exclude, judges apply the Daubert standard to make a ruling on whether an expert’s methods are valid. An appellate court’s determination that the lower court judge improperly applied the standard can result in the initial judge re-evaluating and reinstating your expert testimony.

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