What is Res Ipsa Loquitur and How Does It Apply to My Personal Injury Case?

Most personal injury cases are based on negligence, which is a legal term that means something like “carelessness.” Res ipsa loquitur is a Latin term that literally means “the thing speaks for itself.” It is a legal concept that allows you to take a shortcut to prove that the defendant was negligent by relying on circumstantial evidence. 

Res ipsa loquitur is most often used in the following types of personal injury cases:

Proving res ipsa loquitur creates a “rebuttable presumption” of negligence, not absolute proof of negligence. 

How Plaintiffs Prove Negligence in an Ordinary Personal Injury Case

In an ordinary personal injury claim (one that does not rely on res ipsa loquitur), the plaintiff must prove the following four legal elements to win their claim:

  • The defendant owed the victim a certain duty of care. This might mean the duty to drive safely or the duty to perform surgery on the victim with a certain level of skill.
  • The defendant breached their duty of care to the victim through an act or omission. Duty + breach = negligence.
  • The victim suffered harm. “Harm” must include physical harm, and it may include any additional psychological harm.
  • The defendant’s negligence, established in the first two steps above, was the actual and proximate cause of the harm that the victim suffered.

The victim must prove all four of these legal elements on a “more likely than not” basis.  

Proving Negligence in a Res Ipsa Loquitur Case

A res ipsa loquitur case arises when an accident occurs that common sense tells you could not have happened if somebody hadn’t been negligent. Some examples include:

  • A scalpel remains inside a patient’s body after a kidney stone removal operation;
  • A hammer falls from the roof of a construction site, injuring the victim;
  • A defectively manufactured pharmaceutical injures a patient who takes it; and
  • A piano falls from a window, injuring the victim;

Invoking res ipsa loquitur is the defendant’s way of saying, “Even if I cannot prove exactly how the defendant breached their duty of care, common sense dictates that this accident would not have happened if somebody wasn’t negligent.”

How a “Rebuttable Presumption” Works

Suppose you prove res ipsa loquitur based on facts already in evidence. At that point, a rebuttable presumption of negligence will arise in your favor. This means that the court will find that there was negligence unless the defendant introduces sufficient evidence to rebut your claim of negligence. If they don’t, then you have established negligence. This is not enough by itself to win your claim, but it helps.

Elements of Res Ipsa Loquitur

To establish res ipsa loquitur, you must prove each of the following elements on a “more likely than not” basis:

  • The type of accident that injured you normally would not happen unless somebody was negligent;
  • You were not at fault, or you were no more than 51% at fault; and
  • The defendant owed you a duty of care.

Once you prove these elements, you have a rebuttable presumption of negligence even without proving exactly how the defendant breached their duty of care to you. The type of circumstantial evidence described above is enough.

Negligence vs. Liability

As noted above, duty + breach = negligence. Nevertheless, even if you establish negligence, you must still prove the third and fourth elements of liability. You must prove that you suffered harm (and that the severity of the harm justifies the damages you are claiming), and you must prove that the negligence actually and proximately caused your harm. 


There are several possible defenses that the defendant might rely on, including:

  • “I didn’t owe the defendant any duty of care.” This defense might work if you were injured while trespassing on the defendant’s land, for example.
  • “It wasn’t me.” A doctor accused of medical malpractice might argue that the real culprit was another doctor because the defendant wasn’t even scheduled to perform surgery that day.
  • “The accident was partly the victim’s fault.” If you shared fault with the defendant, a court will reduce or completely eliminate the defendant’s liability based on Pennsylvania comparative negligence principles.
  • “No negligence occurred.” This defense will work if the defendant introduces sufficient evidence to rebut your “rebuttable presumption” that the defendant was negligent.

A Personal Injury Lawyer Can Help

If you cannot directly prove negligence, you might have no choice but to try res ipsa loquitur. Unfortunately, because Pennsylvania courts are typically wary of overusing res ipsa loquitur, it can be difficult to win that way. Relying on internet resources can help, but they can only take you so far. A lawyer can advise you on whether res ipsa loquitur is worth asserting.

Contact an Award-Winning Pennsylvania Personal Injury Lawyer For Help

If you or a loved one has sustained an injury in Harrisburg or elsewhere in the state of Pennsylvania, contact Marzzacco Niven & Associates. Our award-winning Harrisburg personal injury lawyers can help you understand your rights and fight to secure the financial award you may deserve. Please contact us at the nearest location to schedule a free consultation today:

Harrisburg Law Office
945 East Park Drive, Suite 103 Harrisburg, PA 17111
(717) 231-1640

York Law Office
2550 Kingston Road, Suite 210A York, PA 17401
(717) 995-8998

Wyomissing Law Office
833 N. Park Road, Suite 103, Room A Wyomissing, PA 19610
(717) 388-2325

Chambersburg Law Office
79 St. Paul Drive, Suite 1 Chambersburg, PA 17201
(717) 388-2378

Carlisle Law Office
354 Alexander Springs Road Carlisle, PA 17015
(717) 995-8732

Carbondale Law Office
30 Lincoln Avenue, Suite 101 Carbondale, PA 18407
(717) 995-8810

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2173 Embassy Drive, Ste 123, Lancaster Pa 17603
(717) 616-2954

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937 Willow Street, Suite D Lebanon, PA 17042-1140
(717) 995-8963