A fact in the form of a physical property or physical abnormality: in this context, direct observation by the authority or other persons is relevant. The primary source of cognition is the evidentiary instrument (e.g. physical evidence) or the evidentiary act (e.g. inspection). The individual “takes cognizance” of the cognized fact and establishes it. Because the evidence is subject to safeguards, these findings are also made in writing, the most typical form being a note or record. The authorities acting in the case in question thus “translate perceptions and observations into a more stable system of signals – i.e. they produce a derivative proof, a document. At a later stage of the proceedings, the material change is usually presented to the accuser and the court not in its original form but in the form of […] derivative evidence. It thus shows more than it originally showed.”8

Facts in the form of changes in the consciousness of persons: these include subjective memories and objective knowledge (“personal evidence”).9 Among these, one should single out testimonies that describe an experience or an experience in general conceptual-logical terms. The clarity of the meaning of the words in the statement is essential for an accurate understanding of these statements, which the interrogator must ensure by making the statements intelligible while preserving their substance.10 Precise, targeted questioning is a common “tool” for this purpose.

Lőrinczy defines facts as those which serve to establish the facts to be proved.19

In Gödöny’s view, evidence is a fact – obtained from the sources permitted by law and in accordance with the procedural requirements – which is capable of establishing (additional) facts that are relevant to the case.20

Illegal – legal evidence: in the author’s view, the best solution in the former case is to exclude illegal evidence from the proceedings ex lege, i.e. at the level of the Code of Criminal Procedure, and thus not to leave this activity to the discretion of the judiciary; also, the criminalisation of acts committed in connection with illegal evidence is a strong deterrent.21

Irreversible – reversible evidence: in the former case, evidence that comes from sources that can only be examined once, on a case-by-case basis; such evidence therefore carries a higher risk of detection, as (investigative) errors cannot usually be corrected afterwards, and the subject of the evidence is not even perceived by most of the subjects of the proceedings, but is only indirectly known from various documents (e.g. seizure report or photographic evidence).

Original – derivative evidence: in the former case the evidence comes from an original (primary) source, in the latter case from an intermediary (secondary) source. For example, the content of a witness’s testimony may be considered original evidence, while the fact that the witness heard from another person and reported this in his or her testimony may be considered derivative evidence. In the same way, a fact from an original document is original evidence, while a fact from a copy is derivative evidence. There are, of course, many examples in practice where only derivative evidence can be used to (1) locate, (2) verify,22 or (3) replace23 the original evidence. However, original evidence can often become derivative evidence in the course of the proceedings: for example, traces are original evidence, but because they are used in the form of a photograph, they are transformed into derivative evidence. In summary, derivative evidence can, as a general rule, only be taken into account in the proceedings to the extent that it can lead to the acquisition of original evidence.24

Incriminating – exculpatory evidence: this dichotomy is rather relative, since in many cases it is not possible to place a given piece of evidence in only one of the conceptual categories; for example, the content of a confession of a revealing nature as evidence leads to the establishment of criminal liability, while on the other hand it is taken into account as a significant mitigating circumstance in the imposition of a sentence. The discovery of exculpatory evidence is, of course, a legal obligation not only for the defence, but also for the investigating authority and the prosecuting authority (in this evaluation process, of course, the subjective judgments of the law enforcement officer will often be involved).25 It may also be the case that (1) an “incriminating witness” is questioned on facts that could be considered as exculpatory evidence, or (2) the prosecuting authority questions the witness proposed by the defence on inculpatory evidence.26 However, there is also evidence that is both incriminating and exculpatory. Thus, for example, the use of a firearm for self-defence may establish a legitimate defence, but it may already be capable of establishing the offence of misuse of a firearm27 if the offender does not have a licence to use a firearm.

Direct – circumstantial evidence: in the case of the former category, if it is considered credible by the authority (court), the relevant criminal fact can be established “in one step”; in the latter case, however, only the intermediate (so-called “circumstantial”) evidence is established. “in the latter case, it is only possible to establish an intermediate (related) fact, after which further proof is required;28 indirect evidence can therefore be considered more as a probability basis which (merely) generates further suspicions or factual hypotheses;29 indirect evidence is therefore a case where the relevance of the evidence is not clear to the court, which draws some conclusion on the basis of a multi-step logical process.30 Thus, for example, “identification by means of the bullet taken from the victim’s body also directly proves that the crime was committed with that weapon. In contrast, an identification based on a shell casing found at the scene of a crime only proves that the shell casing came from the weapon, but requires separate proof of the connection of the shell casing with the incriminated shot.” 31

According to Lőrinczy, the guilt of the accused can only be established on the basis of circumstantial evidence if the evidence forms a closed logical chain, otherwise the law enforcement officer commits a violation of the law when weighing such evidence. 32

According to Fayer, “circumstantial evidence was accepted as a sufficient basis for conviction, but the ordinary penalty could not be imposed in such a case. In many codes we find an express provision that in the case of half or more, but not complete, evidence, the extraordinary (lighter) penalty should be imposed. The death penalty, which was imposed for most crimes, was not allowed to be imposed on the basis of circumstantial evidence.”33