When a case is settled, the document that brings the case to a close is sometimes referred to as a "full and final release". These words mean that there is no going back. Questions often crop up a year or more later, indicating that the injured person has now found some new symptom that was for whatever reason unknown at the time of the settlement. Or, sometimes the person who settled simply thought the amount of the settlement was too low.
Settlements must be carefully thought out. A settlement is in fact final. Standard releases include language such as this: "I hereby release and forever discharge [insert name] from any and all claims, demands, rights, actions or causes of action on account of or in any way growing out of the accident."
As if this is not enough to cement the finality of the release, again, relatively standard release language foresees potentially unknown effects of the injury and squashes any hope of recovery. Such language often goes like this: "This shall release any and all personal injuries and consequences thereof, including death, and specifically including, also, any injuries which may or may not exist, but which at this time are unknown and unanticipated and which may develop at some time in the future, and all unforeseen developments arising from known injuries resulting from or to result from an accident that occurred on [insert date of accident]."
In case there is any doubt whatsoever, the release puts the icing on the cake by indicating that the settlement represents a "full accord and satisfaction". This language gives the insurance company a legal defense if the case is ever renewed or brought to court in a complaint. Accord and satisfaction is a recognized legal defense that can be raised later, indicating that the claim has been addressed, extinguished and put to rest for eternity.
One question I get about releases is the wording that the release is not an admission of liability and also that the claim was disputed. This is fairly standard. It would be a rare insurance company claims adjuster that would allow a settlement without this common language.
The even more rare exception to the finality of a full final release is where there may have been forgery or fraud. Every day garden variety "I had a lot of bills and I needed the money, I was under stress" does not meet the extremely high burden of proving fraud in this context.
Never even think about settling a personal injury case without retaining an experienced personal injury attorney. Sometimes insurance claims adjusters are in a hurry to close out a file and to get a bonus for settling the case below the reserve that has been set by the company. Add that to the pressure to pay bills and there is a dangerous combination of grabbing money without comprehending the full and true value of the matter. An experienced personal injury attorney has a sense of what a case is worth and has been through the process enough to have perspective that will enable true optimization of the claim.