No defendant should be judged without a fair hearing in which each party is given the opportunity to respond to the evidence against them.
Audi alteram partem is considered to be a principle of fundamental justice or equity or the principle of natural justice in most legal systems. This principle includes the rights of a party or his lawyers to confront the witnesses against him, to have a fair opportunity to challenge the evidence presented by the other party, to summon one's own witnesses and to present evidence, and to have counsel, if necessary at public expense, in order to make one's case properly.
The duty of a judge to give reasons for his/her decisions is a function of due process and therefore justice. Its rationale has two principle aspects.
The first is that fairness surely requires that the parties should be left in no doubt of the bases for the judges’ findings. This is especially so because without a reasoned decision the losing party will not know whether the court has misdirected itself and thus whether he may have an available appeal on the substance of the case. In the absence of reasons it will be impossible to determine whether the judge has made a mistake on the facts or law thus depriving a party of an appeal unless the appeal was itself based on the lack of reasons itself.
The second is that the requirement to give reasons concentrates the mind and the resulting decision is much more likely to be soundly based on the evidence.