Sometimes it is hard to prove who is in the wrong- especially in a personal injury case. People tend to see situations in their favor. The person who is injured feels someone else is to blame for his hurt, while the person that he blames believes it was the injured person's own fault. These types of cases can become exceedingly complicated in a short amount of time. It takes witnesses, testimonies, lawyers, a judge and a jury to determine how these cases should be decided. Often, the court will employ the calculus of negligence to help resolve these sorts of cases. Also known as the hand rule or hand formula, the calculus of negligence helps to determine whether a legal duty of care has been breached.

This hand formula was first used in the case U.S. v. Carroll Towing. In this case, a large boat was improperly tied to a dock, and drifted away into the harbor. It damaged many other boats, and owners brought a lawsuit on the nautical towing company. Eventually, the calculus helped the judge to determine that negligence was indeed a factor in the boat crash, and that the towing company should compensate the other boat owners. There are three variables that define the calculus of negligence.

First, the judge must consider the probability that she will break away. Second, he must determine the gravity of the resulting injury. Third, the court must not the burden of adequate precautions. In a mathematical format, the relationship between these factors reads as " B < PL ." In the formula, B stands for the burden of taking precautions. P is the probability of loss and L is the gravity of loss. The product of P and L must be greater than the burden (B) in order to create a duty of due care for the defendant in the case.

This handy little formula is used in a variety of personal injury cases. By determining a case this way, the court is able to figure out whether or not the injury was incurred out of negligence. If the prosecutor had a contract with the defendant, and both had an understanding that they would not spend money on safety precautions but instead allow harm because it would be more cost-efficient, then the burden may be greater than the other factors. If the harm could have been avoided for less than the cost of the injury, then the individual should have taken precautions. In these cases, the defendant may be liable to pay the injured party for the harm.

Essentially, where damage can be avoided by cost-efficient methods, the legal system requires that precautions are put in place. When the precautions are extremely expensive, the law may not require that they are implemented. Within the hand rule, the "gravity of loss" can be interpreted many ways. Critics complain that this term can mean anything from a dead family member to a broken finger. Still, the courts have the right to determine the rule how they like. In many cases the jury is not told this rule when they enter the court room.

The principles within the hand rule are simple, and many jury members may even use the rule subconsciously, in order to arrive at a conclusion. Once that conclusion is reached, the judge and jury might compensate you for your pain and suffering. You may also be able to receive compensation for medical bills and lost wages. If you are involved in a personal injury case, you will want a legal representative who can carefully assess your situation and provide you with quality representation.