Appeal Determination
Generally, an appeal is decided on the evidence considered in the court below. It is only in exceptional circumstances that additional evidence may be received on appeal. This is because the appeal is reviewing the correctness of the decision of the court below.
A party in litigation is required to make its full case to the court of trial. It would be a recipe for procedural chaos and injustice if parties could rerun a case having lost it, on new grounds and seek to introduce new evidence.
There are very few cases in which new evidence is permitted. New or further evidence may relate to matters which have occurred after the decision. No special consent is required. In this case the failure to put forward the evidence is not due to either party’s default. However, the court still retains discretion not to receive the evidence.
The change in progress of the prognosis of a person who has been injured, would not be sufficient as a grounds for appeal. If some basic assumptions have been falsified by subsequent events ,particularly if this has happened by the act of one party, then the general rule may not apply.
Leave may be granted to admit new evidence which was in existence at the time of the trial. It must have been such that it could not be obtained with due diligence for use in  the trial. It must be such that it would probably have an important influence on the result of the case, though not necessarily decisive. The evidence must be such as is presumptively to be believed and credible. It need not be incontrovertible
Generally further evidence may be given without special leave on an appeal from an interlocutory order. This is because an interlocutory order is not final so that the considerations of finality do not arise to the same extent.
In an appeal court, additional evidence is presented by affidavit or deposition. The principle remains that witnesses are not examined orally. Generally, save in exceptional circumstances the court will not hear and determine issues which have not been tried and decided in the court below. There are some exceptions in the interests of justice.
There is a spectrum of cases in which a new issue is sought to be argued on appeal. The argument on the point may necessarily involve new evidence with consequent effect on the evidence already given. A party may seek to make a new argument which was abandoned in the court below. A party may seek to make an argument diametrically opposed to that advanced in the High Court and the basis on which the case has been argued and perhaps evidence adduced. In such cases, Â the appeal court would not be inclined to grant leave to argue a new point of appeal.
On the other end, the appeal may involve a new formulation of arguments and points advanced in the High Court. A new legal argument may be sought to be advanced which is closely related to arguments already made in the High Court or a refinement of them, Â which is not in any way dependent upon the evidence adduced.
There  is a risk that if a party is excluded from making arguments for a case which might be capable of being won  may be lost. On the other hand, there is potential unfairness to a party who was met a case at the hearing and is asked to meet a different case on appeal.
Essentially parties will only be permitted to raise new issues in limited circumstances.
Review questions of fact
Questions of primary fact are those which depend on the trial judge assessing the credibility and quality of witness evidence. Questions of secondary or inferred facts are different and are based on inferences drawn from facts admitted or determined by the judge.
The appeal court is reluctant to interfere with the findings of  primary fact by the court which has heard the witnesses. The High Court which has heard the witnesses and evidence, is best places to resolve conflicts of oral testimony . The subtleties inflections and countless matters of direct personal impression tend to be distorted or blurred or even totally lost in the transmutation of the live trial into written records.
Where the trial judge drew erroneous conclusions of law from the combination of primary fact and inferences, the appeal may be allowed. If on the facts found and the inferences drawn by the appellate court in accordance with the principles above, it is established to the satisfaction of the appeal court that the conclusion of the trial judge was erroneous, the order will be varied.
The appeal court considers whether the findings of fact made can be supported by credible evidence. The appeal court will only interfere with findings of fact where it cannot in all reason be supported by the evidence.
Where inferences of fact depend on oral evidence or recollection of fact, the appeal court should be slow  to substitute its own inference. In the case of inferences from circumstantial evidence, an appellate court is in as good a position as the trial judge in that regard.
An appellate court proceeds on the findings of facts of the trial judge. The  fact that there is contrary evidence does not alter the position. The fact that there is some evidence before the trial judge which may lead to a different conclusion does not alter the fundamental principle.. The  appellate court should be slow to substitute its own inferences of facts where such depends upon oral evidence.
In the case of experts, although an assessment of the reliability and credibility of a witness may be gained from having been in the courtroom, a decision based on expert evidence is significantly more amenable to analysis on the basis of logic, than a conflict of factual evidence by competing witnesses.
Where a finding of fact is of significant materiality to the overall conclusion it must be accompanied by reasons which set out clearly the basis for the finding. Without this , an appellate court would be unable to determine whether the finding a sustainable. Speculative leaps unsupported by credible evidence will not be sustainable. A bare statement by the trial court that he prefers the evidence of one witness over the other will not be sufficient. Some explanation however brief is required to show the basis for such preference. This does not necessarily involve engagement with an analysis of the competing views of the experts.
Different principles apply to evidence given an affidavit. Where the appeal is based on findings of facts taken from affidavits the appellant must establish an error in those findings that is such as to render the decision untenable or must establish that an essential conflict could not be resolved on the material before the judge.
There are many instances in the Court Rules, where judges have substantial discretion. The appeal court gives great weight to the views of the trial judge. Much will depend on the nature of the discretionary order in itself. In an appropriate case the appeal court has jurisdiction to exercise discretion in a different manner.
If the appellate court can detect a clear error in the manner of approach of the  High Court judge, it is  free to interfere with the decision. Even if it cannot identify such an error the appeal court may allow an appeal if satisfied that justice of the case can only be met by such an approach.
However, the fact that parties are dissatisfied with interlocutory orders made in the High Court does not allow them to use the Court of Appeal as a venue to reargue the application in the hope of persuading the judge to exercise discretion in a somewhat different fashion.
In order for the appeal court to displace the order of the High Court judge in a discovery matter the appellant should be in a position to show that real injustice will be done unless the High Court order is set aside. It is not sufficient for the appellant simply to establish that there was a better or more suitable order that might have been made by the trial judge in the exercise of his or her discretion. A significant margin of appreciation must be allowed to that High Court judge in the review of discretion and interlocutory decision.
The courts are very reluctant to interfere with case management directions. The trial judge must maintain a large measure of discretion over the directions which are appropriate and the measures to be adapted in the event of failure to comply. There would be no reality case management if the court was to regularly entertain appeals from parties who are dissatisfied with directions.
In appropriate cases, the  court will reassess damages. It  will give considerable weight to the findings of the trial judge. In relation to personal injuries, it may reduce or change an award of damages if there is no reasonable proportion between the amount awarded and the courts view of the case.
A case or an issue with in a case may be moot, where the decision can have no practical impact or effect on the resolution of a live controversy between the parties. Where a legal dispute has ceased to exist or where the issue has materially lost its character there is no longer the essential foundation for an action. There is no longer in existence any discord or conflict capable of being judicially determined.
A case is moot when the issues it presents have become hypothetical abstract and when the decision of the court would have no effect in resolving the controversy affecting a real and concrete dispute between the parties.
The court may decline to hear a case on the grounds of mootness. It does not give advisory opinions on purely hypothetical matters.
There may be exceptions. There may be an exceptional circumstance where  one or both parties has a material interest in decision or there is a point of law of exceptional public importance. In this case, the court may determine the point in the interests of the administration of justice. The discretion to hear an appeal where there is no longer a live dispute is exercised with caution
An exception may be a designated test case. Where a case is designated as a test case with reference to broader issues that arise in the proceedings it may be accepted notwithstanding that it is moot. A case may be accepted as a test case if it has the potential to affect other cases. If the case raises a point of law of exceptional public importance this is in favour of it being determined, although it is not itself a reason.
Generally, on appeal will not be allowed in the course of the trial before the termination of the dispute. Very exceptionally, it may be allowed if there are important issues involved.