What is a burden of proof? Simply put, it is the duty that the person bringing a legal case has to show that the allegations being made are true -- or that they are at least likely true -- based on the evidence. There are different standards of proof for different kinds of cases.
For example, in a criminal case, the prosecutor has the burden of proving that the defendant is "guilty beyond a reasonable doubt." The prosecutor must establish that, given all the facts, there is no reasonable conclusion to reach, other than that the defendant committed the crime.
Civil lawsuits, such as a personal injury case, require that the person suing (the plaintiff) meet a different burden of proof, once that isn't as challenging. In civil cases, this burden is generally "by a preponderance of the evidence" or "more likely than not" that the plainitff's allegations are true and the defendant is liable for the plaintiff's harm. (Learn more about proving fault in a civil case.)
Since most personal injury cases involve the legal fault concept known as negligence, let's focus on the plaintiff's burden of proof when it comes to establishing that the defendant was in fact negligent.
Whether we're talking about a car accident case, a slip and fall, or dozens of other kinds of injury cases, meeting the burden of proof means establishing the four elements of negligence: 1) that the defendant owed a duty of care to the plaintiff, 2) that the duty of care was breached, 3) that the defendant's negligence was the cause of an injury; and 4) that the plaintiff was in fact injured.
Duty of Care
The injured plaintiff must first prove that the defendant had a duty to exercise reasonable care and caution in regard to the plaintiff's safety. Sometimes the duty of care is obvious. For instance, there is little question that the law requires that everyone who drives a car exercise caution and safety when operating their vehicle, in order to ensure the safety of others on the road. And a grocery store is required to keep the premises reasonably safe from hazards. But this duty is not absolute. It usually comes down to what is and is not reasonable to expect of the defendant under the circumstances.
Breach of Duty
Once the plaintiff has established that the defendant had a duty to act with reasonable care, the plaintiff must next prove that the defendant breached that duty. Generally, this means proving that the defendant failed to act the way a reasonably careful person would have acted, in the same situation. In a car accident case, a police report showing that the defendant was speeding, driving recklessly, or following too closely can help plaintiff prove that the defendant's conduct was outside the "reasonableness" norm. Witnesses to the incident can also testify as to what they observed, and photographs of the accident scene can paint a picture of what happened.
The plaintiff also must prove that the defendant's conduct caused the injury. That is, the plaintiff must prove that but for the defendant's conduct, the injury would not have happened. Sometimes causation is obvious. If the defendant drove a car over the plaintiff's foot and the plaintiff suffered broken bones, then it is clear that but for the defendant's bad driving, the plaintiff would still have a healthy foot. Other times, causation is more difficult to establish, such as when the plaintiff has a preexisting condition. For instance, a plaintiff who has had previous back problems may have a more difficult time proving that being rear-ended by the defendant's vehicle caused the plaintiff's current back pain.
Injury and Damages
Finally, the plaintiff must prove the details and extent of the resultinginjury. Proof of injury is generally shown through photographic evidence, medical records, and testimony of medical providers. The amount of money that the plaintiff is entitled to, known as "damages," must also be supported by evidince. Why is the plaintiff entitled to the amount that he or she is aking for?
Obviously, medical treatment records and bills are the best evidence of injuries and their extent. And any claim for future medical care will usually need to be supported by expert medical testimony. Tax returns and payroll information from employers can establish lost income. Finally, the plaintiff's own testimony can establish more intangible injuries such as pain and suffering and loss of enjoyment.