Who Is the Plaintiff & Who Is the Defendant in a Personal Injury Case?

Every personal injury case involves two main parties: the plaintiff and the defendant. The plaintiff is the one who files the claim (or lawsuit), whereas the defendant is the one against whom the claim or lawsuit is filed.

Let’s take a closer look.

The Plaintiff: Rights & Legal Responsibilities

A plaintiff is the person who starts a claim or lawsuit. In a personal injury case, the plaintiff is usually the injured person, the one who was hurt because someone else was careless or did something wrong. The plaintiff is the one seeking compensation or, with a lawsuit, the one asking the court to make things right by awarding money for medical bills, lost wages, pain and suffering, and other damages.

Think of it this way: if you were hurt in a car accident, at work, or by a defective product, and you filed a legal case to get compensation, you would be the plaintiff.

What Responsibilities Does the Plaintiff Have?

The plaintiff in a personal injury case has certain legal responsibilities. Most importantly, the plaintiff has what is known as “the burden of proof.” This means that the plaintiff is the one who must prove that the other party (the defendant) is legally responsible (liable) for the plaintiff’s injuries and losses (damages).

In most cases, establishing liability means proving four essential elements of negligence:

• Duty of Care: The first element of negligence is the duty of care. This refers to someone’s legal obligation to act with reasonable care to avoid harming others. For example, drivers must operate their vehicles safety and follow all traffic laws, property owners must keep their premises reasonably safe, and employers must provide safe working environments for their employees.
• Breach: The second element of negligence involves proving that the duty of care was breached. This occurs when someone fails to act as a reasonably careful person would under the same or similar circumstances. In other words, they were careless, reckless, or negligent. Examples of breaches of the duty of care include texting while driving, ignoring known safety hazards at a worksite, or failing to remove or warn of unsafe property conditions, such as a spill.
• Causation: The third element of negligence is causation. This is the link between the person’s negligent actions or inactions and the victim’s injuries. It’s not enough to show that someone acted carelessly or recklessly; you must also prove that their actions directly caused the injury. There are two parts to causation: actual cause, meaning the injury wouldn’t have happened if not for the defendant’s conduct, and proximate cause, meaning the injury was a foreseeable result of the defendant’s actions.
• Damages: The fourth and final element of negligence involves proving that the plaintiff showed actual harm because of the injury. This harm can take many forms, including physical injuries, financial losses such as medical expenses and missed wages, or mental and emotional suffering. The compensation awarded for such harm is known as “damages,” and without real, measurable damages, there is no basis for a claim—even if the defendant was clearly negligent.

In addition to the burden of proof, the plaintiff in a personal injury claim also has the following legal duties:

• Acting within the designated time frame (statute of limitations) to file a claim or lawsuit
• Filing a lawsuit properly, including stating the facts of the case and outlining its legal basis (e.g., negligence)
• Responding to discovery requests, including answering any written questions, providing a deposition, and producing requested documents
• Mitigating damages by seeking appropriate medical treatment, avoiding actions that could worsen injuries, and following through with care
• Complying with all court orders and legal procedures, including attending required hearings and mediations

By fulfilling these obligations, the plaintiff establishes the strongest possible foundation for their case.

The Defendant’s Role & Legal Obligations

In a personal injury case, the defendant is the person, company, or entity being sued by the injured party (plaintiff). The plaintiff claims that the defendant’s negligence or wrongful conduct caused harm, and the legal system gives the defendant the opportunity to respond to and defend against the plaintiff’s claims.

While the burden of proof lies with the plaintiff, the defendant still has an active role in the legal process. They have specific legal obligations that must be met once a lawsuit is filed.

Responding to the Lawsuit

Once a personal injury lawsuit is filed, the defendant is formally notified through a legal document called a summons and complaint. The defendant is legally required to respond by filing an answer. This is a document that either admits or denies the allegations and outlines any defenses.

Failing to respond within the court’s deadline can result in a default judgment, meaning the plaintiff automatically wins the case. Most corporate or insured defendants will have legal teams in place to handle these filings quickly.

Participating in the Discovery Process

The defendant is obligated to take part in discovery, a legal phase where both sides exchange evidence and information.

This may include:

• Providing documents such as safety records, internal reports, or insurance policies
• Answering written questions (interrogatories)
• Participating in depositions (oral testimony under oath)

Defendants must respond truthfully and completely or they risk legal penalties, including court sanctions or exclusion of evidence at trial.

Preserving Evidence

Once a defendant becomes aware of a potential or active lawsuit, they are legally required to preserve any evidence related to the incident.

This might include:

• Surveillance footage
• Maintenance logs
• Vehicle or equipment involved in the accident
• Emails or internal communications

Intentional destruction of evidence (called spoliation) can severely damage a defendant’s credibility and may lead to court-imposed consequences.

Complying with Court Orders

Throughout the litigation process, the defendant must follow all court rules and orders. This includes attending required hearings, participating in mediation if ordered, and honoring any rulings the judge makes.

Common Defenses in Personal Injury Cases

The defendant has the right to contest the plaintiff’s claim. The exact defense will depend on the specific details of the case, but certain arguments tend to arise more often than others.

Defendants may claim that:

• They were not negligent
• The plaintiff was partially or fully at fault
• The injuries weren’t caused by the incident
• The plaintiff’s damages are exaggerated or unrelated

They may also offer affirmative defenses, such as claiming the plaintiff voluntarily assumed the risk of injury. In many cases, defendants will try to settle the case to avoid the uncertainty and cost of trial, but they will almost always offer a low settlement to start. This is where negotiations begin—and why it’s a good idea to always work with an experienced personal injury lawyer, even if you want to avoid court.

Can There Be Multiple Plaintiffs or Defendants in a Personal Injury Case?

In many personal injury cases, more than one person may be harmed, or more than one party may be legally responsible. When this happens, the case may involve multiple plaintiffs (those filing the lawsuit) or multiple defendants (those being sued). These cases often involve large-scale incidents, overlapping responsibilities, or shared liability.

Multiple Plaintiffs: Mass Tort or Class Action Cases

When many people are injured by the same event, product, or act of negligence, they may come together to file a joint legal action. This may be done as a mass tort (individual cases consolidated for efficiency) or a class action (one case representing a larger group).

Some examples include:

• Plant or refinery explosions that injure dozens of workers and nearby residents
• Defective drugs or medical devices that cause widespread harm to patients
• Maritime disasters where multiple crew members or passengers suffer injury or death

In these cases, each plaintiff may have unique injuries or damages, but they share a common legal claim against the same defendant or group of defendants.

Multiple Defendants: Shared or Divided Liability

Sometimes, more than one party contributes to the cause of an injury. In those cases, the plaintiff may file lawsuits against multiple defendants.

Examples of this include:

• A construction worker falls from scaffolding that collapses due to improper setup. An investigation reveals that the general contractor failed to ensure that safety protocols were being followed across the job site, while a scaffolding subcontractor used outdated or improperly secured equipment and skipped required inspections.
• A family is seriously injured in a highway collision with an 18-wheeler. Facts show that the truck driver was speeding and had exceeded the number of hours allowed behind the wheel. Meanwhile, the trucking company had ignored red flags in the driver’s logbooks indicating that he often exceeded hours-of-service rules. To make matters worse, a brake manufacturer supplied defective parts that contributed to the truck’s inability to stop.
• An oil refinery worker is severely burned after a pressure valve explodes. The investigation determines that the employer failed to perform regular safety checks or train workers in emergency shutoff procedures. Additionally, the valve manufacturer knew the part had a design flaw but failed to issue a recall or adequate warnings.

In each of these scenarios, multiple defendants played a role in the victims’ injuries. As a result, victims’ have the right to file claims against multiple parties.

When there are multiple defendants, they may be held jointly or separately liable depending on the facts of the case and how responsibility is assigned under the law. These cases often require detailed investigation to untangle who did what, when, and how it contributed to the injury.

Trusted in the Most Complex Cases Nationwide

Arnold & Itkin has helped countless plaintiffs fight for justice. Whether we’re representing multiple workers injured in a plant explosion or going toe-to-toe with powerful corporate defendants, we have the proven track record, team, and trial experience to win.

When the stakes are high, people turn to us because we don’t back down, and we don’t settle for less than our clients deserve.