Oral testimony by the parties in civil proceedings was introduced in Austria in 1895. Norway followed suit in 1915, Denmark in 1919, Germany in 1933, and Sweden in 1948. Party testimony is generally heard in the same way as the evidence of witnesses, but there are some essential differences. In some countries, the interrogation of parties is a subsidiary source of evidence to be used only when all other means have been exhausted; in others (e.g., Norway, Sweden, Austria, Brazil), parties are heard before witnesses. In some countries, both parties must be heard; in others, only one party may be heard upon motion of the opponent. The judge decides whether the parties are to be heard; this contrasts with the procedure with witnesses, who are heard only after having been nominated by the parties.

In most cases, the parties do not have to confirm their testimony by oath, but the court may decree that one of the parties must swear. In Swedish law, for example, the parties must solemnly declare that they have told the truth.

Expert evidence

Expert witnesses must have specialized knowledge, skill, or experience in the area of their testimony. For the most part, they do not testify concerning facts but draw inferences from them. With a few exceptions, they are treated in Anglo-American law as ordinary witnesses and are brought before the court by the parties in the same manner as other witnesses. Although ordinary witnesses are generally allowed to testify only concerning facts and not to express opinions, an exception to this rule is made for the expert, who must, of course, be allowed to give his opinion.

Generally speaking, anyone with special knowledge may be an expert in his respective field. In Anglo-American law, the expert is designated by the party, while in continental European law the court decides who may be an expert, generally selecting from a list on file in the court so as to guarantee that the experts designated are impartial. Experts may not, therefore, be cited by the parties.

The oral interrogation of experts is customary in Anglo-American law and proceeds, with a few exceptions, under the same rules for the interrogation of ordinary witnesses.

Under Continental rules of procedure, on the other hand, expert opinions are generally given in written form. Experts are allowed a rather wide scope of discretion, especially when the opinion involves scientific findings that often cannot be checked by the judge. But under some continental European rules, the parties or their attorneys may request that the experts testify before the court to defend their written opinion and tell how they arrived at it.

Documentary evidence

Documentary evidence is in many respects considered better than the evidence furnished by witnesses, about which there has always been a certain amount of suspicion. Documentary evidence differs considerably from the evidence of witnesses and is dealt with under special rules.

Criteria for establishing the authenticity of documents are only important if authenticity is contested. This is often impossible, however, if a presumption favouring the authenticity of a public document exists—which it frequently does under continental European law. Under Anglo-American law, a party may serve the adversary with a written request to corroborate the authenticity of any relevant document. Direct evidence of authenticity may be gotten through the testimony of persons who signed the original documents. This is often impossible, however, and in this case circumstantial evidence is permitted. In some civil-law countries, documents are proved genuine by special proceedings. In other continental European countries, a document may be proved genuine by any type of evidence.

The obligation to present documents in the Anglo-American system derives from the best evidence rule. If the original document is in the hands of a third person or the opponent, the party that must supply proof can ask the court for a writ of sub poena duces tecum compelling the third party to produce the document in court. If the original is not produced after this, secondhand evidence of its existence is then permitted. In Continental law there is no similar obligation to produce documents. The adversary or third persons can only be ordered to do so if there is a positive obligation under the substantive law. Among European countries, only Sweden has developed any extensive obligation for the parties to produce documents.

Extrinsic proof of the contents of documents in Anglo-American law is admitted only in special cases, since oral evidence is inadmissible to vary, contradict, or add to the terms of a written agreement—a rule that makes many documents conclusive as evidence. The method of Anglo-American law in this particular area is consequently negative, since evidence outside the content of the document is in principle not admissible. Continental law follows the medieval method, by attributing a certain value as evidence to particular documents, which is binding on the judge.

The consideration of documentary evidence by the judge therefore tends to be restricted, since the document itself furnishes conclusive proof if evidence by reference to facts outside the document is inadmissible. In most Continental laws, judges are bound by presumptions in this respect, and only in Swedish law are there no provisions restricting free judicial consideration of documentary evidence.

Real evidence

The remaining form of evidence is so-called real evidence, also known as demonstrative or objective evidence. This is naturally the most direct evidence, since the objects in question are inspected by the judge or jury themselves. Problems arise in this area over who is obliged to present objects for inspection or to actually undergo inspection. The use of the jury system in Anglo-American law has made it necessary that any real evidence be shown to be both relevant and completely genuine before it may be admitted as proof. The exhibit of real evidence may sometimes be directly connected with the case (for example, when a weapon is shown to the court), or it may involve something used to illustrate testimony, as, for example, a model or skeleton to clarify testimony about an injury. In any case, real evidence may not be accepted as legal proof unless it is authenticated by the testimony of witnesses.