The specific procedures for appealing, including even whether there is a right of appeal from a particular type of decision, can vary greatly from country to country. Even within a jurisdiction, the nature of an appeal can vary greatly depending on the type of case.
An appellate court is a court that hears cases on appeal from another court. Depending on the particular legal rules that apply to each circumstance, a party to a court case who is unhappy with the result might be able to challenge that result in an appellate court on specific grounds. These grounds typically could include errors of law, fact, or procedure (in the United States, due process).
In different jurisdictions, appellate courts are also called appeals courts, courts of appeals, superior courts, or supreme courts.
The appellant is the party who, having lost part or all their claim in a lower court decision, is appealing to a higher court to have their case reconsidered. This is usually done on the basis that the lower court judge erred in the application of law, but it may also be possible to appeal on the basis of court misconduct, or that a finding of fact was entirely unreasonable to make on the evidence.
The appellant in the new case can be either the plaintiff (or claimant), defendant, or respondent (appellee) from the lower case, depending on who was the losing party. The winning party from the lower court, however, is now the respondent. In unusual cases the appellant can be the victor in the court below, but still appeal. For example, in Doyle v Olby (Ironmongers) Ltd  2 QB 158, the claimant appealed (successfully) on the basis that, although he won in the court below, the lower court had applied the wrong measure of damages and he had not been fully recompensed.
An appellee is the party to an appeal in which the lower court judgment was in its favor. The appellee is required to respond to the petition, oral arguments, and legal briefs of the appellant. In general, the appellee takes the procedural posture that the lower court's decision should be affirmed.
In tort, equity, or other civil matters either party to a previous case may file an appeal. In criminal matters, however, the state or prosecution generally has no appeal as of right. And due to the double jeopardy principle, in the United States the state or prosecution may never appeal a jury or bench verdict of acquittal. But in some jurisdictions, the state or prosecution may appeal as of right from a trial court's dismissal of an indictment in whole or in part or from a trial court's granting of a defendant's suppression motion. Likewise, in some jurisdictions, the state or prosecution may appeal an issue of law by leave from the trial court and/or the appellate court. The ability of the prosecution to appeal a decision in favor of a defendant varies significantly internationally. All parties must present grounds to appeal, or it will not be heard.
By convention in some law reports, the appellant is named first. This can mean that where it is the defendant who appeals, the name of the case in the law reports reverses (in some cases twice) as the appeals work their way up the court hierarchy. This is not always true, however. In the United States federal courts, the parties' names always stay in the same order as the lower court when an appeal is taken to the circuit courts of appeals, and are re-ordered only if the appeal reaches the United States Supreme Court.
The key distinguishing factor between direct and collateral appeals is that the former only reviews evidence that was presented in the trial court, but the latter allows review of evidence dehors the record: depositions, affidavits, and witness statements that did not come in at trial. The standard for post-conviction relief is high, typically requiring the petitioner to demonstrate that the evidence presented was not available in the usual course of trial discovery.
Relief in post-conviction is rare and is most often found in capital or violent felony cases. The typical scenario involves an incarcerated defendant locating DNA evidence demonstrating the defendant's actual innocence.
The specific rules of the legal system will dictate exactly how the appeal is officially begun. For example, the appellant might have to file the notice of appeal with the appellate court, or with the court from which the appeal is taken, or both.
Some courts have samples of a notice of appeal on the court's own web site.
The deadline for beginning an appeal can often be very short: traditionally, it is measured in days, not years. This can vary from country to country, as well as within a country, depending on the specific rules in force.
If the appellate court finds no defect, it "affirms" the judgment. If the appellate court does find a legal defect in the decision "below" (i.e., in the lower court), it may "modify" the ruling to correct the defect, or it may nullify ("reverse" or "vacate") the whole decision or any part of it. It may, in addition, send the case back ("remand" or "remit") to the lower court for further proceedings to remedy the defect.
In some cases, an appellate court may review a lower court decision de novo (or completely), challenging even the lower court's findings of fact. This might be the proper standard of review, for example, if the lower court resolved the case by granting a pre-trial motion to dismiss or motion for summary judgment which is usually based only upon written submissions to the trial court and not on any trial testimony.
Another situation is where appeal is by way of re-hearing. Certain jurisdictions permit certain appeals to cause the trial to be heard afresh in the appellate court. An example would be an appeal from a Magistrates' court to the Crown Court in England and Wales.
Sometimes, the appellate court finds a defect in the procedure the parties used in filing the appeal and dismisses the appeal without considering its merits, which has the same effect as affirming the judgment below. (This would happen, for example, if the appellant waited too long, under the appellate court's rules, to file the appeal.) In England and many other jurisdictions, however, the phrase appeal dismissed is equivalent to the U.S. term affirmed; and the phrase appeal allowed is equivalent to the U.S. term reversed.
Generally, there is no trial in an appellate court, only consideration of the record of the evidence presented to the trial court and all the pre-trial and trial court proceedings are reviewed—unless the appeal is by way of re-hearing, new evidence will usually only be considered on appeal in very rare instances, for example if that material evidence was unavailable to a party for some very significant reason such as prosecutorial misconduct.
In some systems, an appellate court will only consider the written decision of the lower court, together with any written evidence that was before that court and is relevant to the appeal. In other systems, the appellate court will normally consider the record of the lower court. In those cases the record will first be certified by the lower court.
The appellant has the opportunity to present arguments for the granting of the appeal and the appellee (or respondent) can present arguments against it. Arguments of the parties to the appeal are presented through their appellate lawyers, if represented, or pro se if the party has not engaged legal representation. Those arguments are presented in written briefs and sometimes in oral argument to the court at a hearing. At such hearings each party is allowed a brief presentation at which the appellate judges ask questions based on their review of the record below and the submitted briefs.
It is important to note that in an adversarial system appellate courts do not have the power to review lower court decisions unless a party appeals it. Therefore if a lower court has ruled in an improper manner or against legal precedent that judgment will stand even if it might have been overturned on appeal.
A trial de novo is usually available for review of informal proceedings conducted by some minor judicial tribunals in proceedings that do not provide all the procedural attributes of a formal judicial trial. If unchallenged, these decisions have the power to settle more minor legal disputes once and for all. If a party is dissatisfied with the finding of such a tribunal, one generally has the power to request a trial de novo by a court of record. In such a proceeding, all issues and evidence may be developed newly, as though never heard before, and one is not restricted to the evidence heard in the lower proceeding. Sometimes, however, the decision of the lower proceeding is itself admissible as evidence, thus helping to curb frivolous appeals.
In an appeal on the record from a decision in a judicial proceeding, both appellant and respondent are bound to base their arguments wholly on the proceedings and body of evidence as they were presented in the lower tribunal. Each seeks to prove to the higher court that the result they desired was the just result. Precedent and case law figure prominently in the arguments. In order for the appeal to succeed, the appellant must prove that the lower court committed reversible error, that is, an impermissible action by the court acted to cause a result that was unjust, and which would not have resulted had the court acted properly. Some examples of reversible error would be erroneously instructing the jury on the law applicable to the case, permitting seriously improper argument by an attorney, admitting or excluding evidence improperly, acting outside the court's jurisdiction, injecting bias into the proceeding or appearing to do so, juror misconduct, etc. The failure to formally object at the time, to what one views as improper action in the lower court, may result in the affirmance of the lower court's judgment on the grounds that one did not "preserve the issue for appeal" by objecting.
In cases where a judge rather than a jury decided issues of fact, an appellate court will apply an abuse of discretion standard of review. Under this standard, the appellate court gives deference to the lower court's view of the evidence, and reverses its decision only if it were a clear abuse of discretion. This is usually defined as a decision outside the bounds of reasonableness. On the other hand, the appellate court normally gives less deference to a lower court's decision on issues of law, and may reverse if it finds that the lower court applied the wrong legal standard.
In some rare cases, an appellant may successfully argue that the law under which the lower decision was rendered was unconstitutional or otherwise invalid, or may convince the higher court to order a new trial on the basis that evidence earlier sought was concealed or only recently discovered. In the case of new evidence, there must be a high probability that its presence or absence would have made a material difference in the trial. Another issue suitable for appeal in criminal cases is effective assistance of counsel. If a defendant has been convicted and can prove that his lawyer did not adequately handle his case and that there is a reasonable probability that the result of the trial would have been different had the lawyer given competent representation, he is entitled to a new trial.
In the United States, a lawyer traditionally starts an oral argument to any appellate court with the words "May it please the court."
After an appeal is heard, the mandate is a formal notice of a decision by a court of appeal; this notice is transmitted to the trial court and, when filed by the clerk of the trial court, constitutes the final judgment on the case, unless the appeal court has directed further proceedings in the trial court. The mandate is distinguished from the appeal court's opinion, which sets out the legal reasoning for its decision. In some U.S. jurisdictions the mandate is known as the remittitur.
In most jurisdictions the normal and preferred way of seeking appellate review is by filing an appeal of the final judgment. Generally, an appeal of the judgment will also allow appeal of all other orders or rulings made by the trial court in the course of the case. This is because such orders cannot be appealed as of right. However, certain critical interlocutory court orders, such as the denial of a request for an interim injunction, or an order holding a person in contempt of court, can be appealed immediately although the case may otherwise not have been fully disposed of.
In American law, there are two distinct forms of appellate review, direct and collateral. For example, a criminal defendant may be convicted in state court, and lose on direct appeal to higher state appellate courts, and if unsuccessful, mount a collateral action such as filing for a writ of habeas corpus in the Federal courts. Generally speaking, "[d]irect appeal statutes afford defendants the opportunity to challenge the merits of a judgment and allege errors of law or fact. ... [Collateral review], on the other hand, provide[s] an independent and civil inquiry into the validity of a conviction and sentence, and as such are generally limited to challenges to constitutional, jurisdictional, or other fundamental violations that occurred at trial." Graham v. Borgen, __ F 3d. __ (7th Cir. 2007) (no. 04-4103) (slip op. at 7) (citation omitted).
In Anglo-American common law courts, appellate review of lower court decisions may also be obtained by filing a petition for review by prerogative writ in certain cases. There is no corresponding right to a writ in any pure or continental civil law legal systems, though some mixed systems such as Quebec recognize these prerogative writs.