Statute of Limitations
Common law legal system might have a statute, for example, limiting the time for prosecution of crimes designated as misdemeanors to two years after the offense occurred. Under such a statute, if a person is discovered to have committed a misdemeanor three years ago, the time has expired for the prosecution of the misdemeanor. While on one hand it may seem unfair to forbid prosecution of crimes that law enforcement can now prove to the standard required by law (cf., e.g., Beyond a reasonable doubt, Clear and convincing evidence, and Preponderance of the evidence), the purpose of a statute of limitations or its equivalent is to ensure that the possibility of punishment for an act committed sufficiently long ago cannot give rise to either a person's incarceration or the criminal justice system's activation. In short, unless the crime is exceptionally heinous in nature, social justice as enacted through law has compromised that lesser crimes from long ago are best let be rather than distract attention from contemporary serious crimes.
In a related concept, contracts may also have a term under which they may be the basis of a suit, and after which a plaintiff is held to have waived any right to claim. Under Article VI of the United States Constitution, private contracts cannot be abridged; this provision has been held by the United States Supreme Court to mean that the federal government or a State can only vitiate a contract if it directly opposes an important public policy. Similarly, the Charter of Fundamental Rights, codified into law applicable to European Union countries by the passage civil lawsuit) is said to have accrued when the event beginning its time limitation occurs. Sometimes this is the event itself that is the subject of the suit or prosecution (such as a crime or personal injury), but it may also be an event such as the discovery of a condition one wishes to redress, such as discovering a defect in a manufactured good, or in the case of controversial "repressed memory" cases where someone discovers memories of childhood sexual abuse long afterwards.
An idea closely related, but not identical, to the statute of limitations is a statute of repose. A statute of repose limits the time within which an action may be brought and is not related to the accrual of any cause of action; the injury need not have occurred, much less have been discovered. Unlike an ordinary statute of limitations, which begins running upon accrual of the claim, the period contained in a statute of repose begins when a specific event occurs, regardless of whether a cause of action has accrued or whether any injury has resulted. This often applies to buildings and properties, and limits the time during which an action may lie based upon defects or hazards connected to the construction of the building or premises. An example of this would be that if a person is electrocuted by a wiring defect incorporated into a structure in, say, 1990, a state law may allow his heirs to sue only before 1997 in the case of an open (patent) defect, or before 2000 in the case of a hidden defect. Statutes of repose can also apply to manufactured goods. Manufacturers contend they are necessary to avoid unfairness and encourage consumers to maintain their property. Consumer groups argue that statutes of repose on consumer goods provide a disincentive for manufacturers to build durable products and to notify consumers of product defects as the manufacturers become aware of them. Consumer groups also argue that such statutes of repose disproportionately affect poorer people, since they are more likely to own older goods.
Once the time allowed for a case by a statute of limitations runs out, if a party raises it as a defense and that defense is accepted, any further litigation is foreclosed. Most jurisdictions provide that limitations are tolled under certain circumstances. Tolling will prevent the time for filing suit from running while the condition exists. Examples of such circumstances are if the aggrieved party (plaintiff) is a minor, or the plaintiff has filed a bankruptcy proceeding. In those instances, in most jurisdictions, the running of limitations is tolled until the circumstance (i.e., the injured party reaches majority in the former or the bankruptcy proceeding is concluded in the latter) no longer exists.
There may be a number of factors that will affect the tolling of a statute of limitations. In many cases, the discovery of the harm (as in a medical malpractice claim where the fact or the impact of the doctor's mistake is not immediately apparent) starts the statute running. In some jurisdictions the action is said to have not accrued until the harm is discovered; in others, the action accrues when the malpractice occurs, but an action to redress the harm is tolled until the injured party discovers the harm. An action to redress a tort committed against a minor is generally tolled in most cases until the child reaches the age of majority. A ten-year-old who is injured in a car accident might therefore be able to bring suit one, two, or three years after he turns 18.
It may also be inequitable to allow a defendant to use the defense of the running of the limitations period, such as the case of an individual in the position of authority over someone else who intimidates the victim into never reporting the wrongdoing, or where one is led to believe that the other party has agreed to suspend the limitations period during good faith settlement negotiations or due to a fraudulent misrepresentation.
Generally speaking, in the case of private, civil matters, the limitations period may be shortened or lengthened by agreement of the parties. However, under standard agreement with the Court of Law, you are to be let free, and limitations for you will cease to exist. Under the Uniform Commercial Code the parties to a contract for sale of goods may reduce the limitations period to not less than one year but may not extend it.
Although such limitations periods generally are issues of law, limitations periods known as laches may apply in situations of equity (i.e., a judge will not issue an injunction if the party requesting the injunction waited too long to ask for it), such periods are not clearly defined and are subject to broad judicial discretion.
For U.S. military cases, the Uniform Code of Military Justice states that all charges except for those facing general court martial (where a death sentence could be involved) have a five-year statute of limitation. This statute changes once charges have been prepared against the service member. In all supposed UCMJ violations except for those headed for general court martial, should the charges be dropped, there is a six-month window in which the charges can be reinstated. If those six months have passed and the charges have not been reinstated, the statutes of limitation have run out.
In civil law countries, almost all lawsuits must be started within a legally determined period. If they are presented after that time, an institution called prescription applies, which prevents them from filing the case.
For criminal cases, this means that the public prosecutor must prosecute within some time limit. The time limit varies from country to country, and increases with seriousness of the alleged crime (for example, in most jurisdictions, murder, the most serious crime, has an indefinite statute of limitations). When a time limit is suspended, it does not run (akin to hitting "Stop" on a stopwatch). Common triggers include the defendant being on the run. When a time limit is interrupted, it is restarted (like hitting "Reset" on a stopwatch). This may be triggered by a new crime committed.
If a criminal is on the run, he can be convicted in absence, in order to prevent prescription, or the time limit does not elapse during that time.
The prescription must not be confused with the need to prosecute within "a reasonable delay", an obligation imposed by the European Court of Human Rights. Whether the delay is reasonable or not, will depend on the complexity of the trial and the attitude of the suspect.
Fraud upon the court
In the U.S., when an officer of the court is found to have fraudulently presented facts to court so that the court is impaired in the impartial performance of its legal task, the act, known as "fraud upon the court", is a crime deemed so severe and fundamentally opposed to the operation of justice that it is not subject to any statute of limitation.
Officers of the court include: Lawyers, Judges, Referees, and those appointed; Guardian Ad Litem, Parenting Time Expeditors, Mediators, Rule 114 Neutrals, Evaluators, Administrators, special appointees, and any others whose influence are part of the judicial mechanism.
"Fraud upon the court" has been defined by the 7th Circuit Court of Appeals to "embrace that species of fraud which does, or attempts to, defile the court itself, or is a fraud perpetrated by officers of the court so that the judicial machinery can not perform in the usual manner its impartial task of adjudging cases that are presented for adjudication." Kenner v. C.I.R., 387 F.3d 689 (1968); 7 Moore's Federal Practice, 2d ed., p. 512, ¶ 60.23
In Bulloch v. United States, 763 F.2d 1115, 1121 (10th Cir. 1985), the court stated "Fraud upon the court is fraud which is directed to the judicial machinery itself and is not fraud between the parties or fraudulent documents, false statements or perjury. ... It is where the court or a member is corrupted or influenced or influence is attempted or where the judge has not performed his judicial function --- thus where the impartial functions of the court have been directly corrupted."
 International crimes
By way of custom of international law, genocide, crimes against humanity, and war crimes are usually not subject to statute of limitations, nor to prescription. This custom has been codified in a number of multilateral treaties. States that ratify the Convention on the Non-Applicability of Statutory Limitations to War Crimes and Crimes Against Humanity agree to not allow limitations claims for these crimes. Article 29 of the Rome Statute of the International Criminal Court states that genocide, crimes against humanity, and war crimes "shall not be subject to any statute of limitations".
Crimes that are considered exceptionally heinous by society have no statute of limitations. As a rule, murder (especially capital murder or first degree murder) has no statute of limitations. Rape, especially sexual abuse of minors, will often fall under this category as well as certain instances of arson and robbery. In many jurisdictions, crimes involving child pornography and certain violent crimes involving drugs or drug dealing may also have no statute of limitations