CONCLUSIO IN CAUSA. - According to the CIC, the c. in c. is nothing other than the termination of the instructional or probative period of the trial (can. 1860 § 1). This has always been its proper effect, even if the theoretical concept has changed somewhat over the course of time, as frequently happens.
The c. in c. is already found in use, introduced by custom (A. Reiffenstuel, Ius canonicum universum, I, II, t. 27, n. 48), rather than by any express precept of law, in very remote times (c. 11, C. XXX, q. 5; c. 8, X, II, 38 etc.). Clement V in his celebrated constitution Saep of 19 Nov. 1306 (c. 2, V, 11 in Clem.) granted that in summary judgments one might proceed to sentence conclusione non facta. Moreover, while the c. in c. has fallen into disuse in civil procedures, the Church has tenaciously maintained it in her discipline down to the CIC (cf. S. C. S. Off., Instr. ad Episcopos Rit. Orient., 20 June 1883, t. III, n. 22; S. C. de Prop. Fide, Instr. a. 1883, n. 22; Lex. propr. S. R. Rotae et Sign. Ap., 20 June 1908, c. 27 §§ 1, 2; Regulae servandae apud S. R. R. Tribun., 4 Aug. 1910, § 51; Normae S. R. Rotae Tribun., 29 June 1934, n. 121; S. C. de Sacr. Instr., 15 Aug. 1936, aa. 177 ff.).
In the ancient concept the c. in c. was the renunciation made by the parties of further proofs and the consequent remission of the cause to the judge's decision (F. Schmalzgruber, Ius ecclesiasticum universum, I, II, t. 27, n. 1), which could be made expressly or tacitly, absolutely or under condition. Today, however, the conclusion is nothing but a phase of the trial that occurs automatically, that is, when one of the three hypotheses contemplated in § 2 of can. 1860 takes place, which states verbatim: "this conclusion occurs whenever the parties, interrogated by the judge, declare that they have nothing further to adduce, or the time appointed by the judge for producing the proofs has elapsed (cf. can. 1731 n. 2), or the judge himself declares the cause sufficiently instructed." Once any of these three facts has occurred, the conclusion takes place forthwith. The judge, however, to avoid equivocation or uncertainty, must always declare the conclusion to have occurred by a specific decree, whatever the fact that provoked it may have been (ibid. § 3).
This decree, which is lacking in the current norms of the Rota (cf. a. 121) and which in the Instruction of the S. C. of the Sacraments (s. 177 § 1) constitutes the conclusion, does not seem to be essential to the trial, just as the conclusion itself was not, according to common doctrine (cf. R. Maranta, Speculum aureum, p. 4, d. 9 n. 23).
In collegiate tribunals the decree is given by the president (S. C. de S. Instr. a. 177 § 1). The c. in c. pursues two principal aims: to remove all uncertainty about the useful time granted to the parties for producing their proofs, and to hasten the instruction of the cause by preventing useless or malicious delays.
In the canonical trial the conclusion, even if it does not touch its substance, has notable importance, since effects of notable significance are connected to it.
The first and fundamental effect is the closing of the instructional period and the consequent preclusion of new proofs (can. 1861 § 1). This preclusion, however, is not absolute; new proofs are admitted in causes that do not pass into res judicata, just as there may be admitted both documents found after the conclusion has occurred and those that could not be produced in time, as well as witnesses who could not be produced before the conclusion (ibid.). In any case, the admission of new proofs is decreed by the judge at the request of a party, after the other party has been heard and given sufficient time to become acquainted with the new proofs adduced and to defend itself against them; otherwise the judgment would be null (can. 1861 § 2). Moreover, the preclusion of new proofs does not include either the exceptions of absolute incompetence and of excommunication, which may be produced at any stage and grade of the trial (can. 1628 §§ 1, 2), or judicial confession, or the decisive oath, which likewise may be deferred at any stage and moment of the suit (can. 1834 § 1). Another effect of the conclusion is the opening of the discussion of the cause, for which the judge must appoint for the parties, according to his prudent judgment, a convenient space of time to present, for themselves or through their advocates, their defenses and replies (can. 1862 § 2). And here a notable difference must be noted between the procedure of the Rota and that of the CIC: while in the latter the conclusion precedes the discussion, which comes immediately after the presentation of the proofs, in the Rota, by tradition, which perhaps corresponds better to the ancient concept (cf. A. Reiffenstuel, loc. cit.), the conclusion occurs after the parties have exchanged with one another the replies to their respective defenses (a. 121). There are also other effects of the conclusion: thus, after the conclusion no new questions may be put to the parties (can. 1742 § 3); the voluntary intervention of a third party in the cause is not admitted (can. 1852 § 2); death, change of state, cessation in office do not interrupt the instance (can. 1733 n. 2), etc. In ancient times it was disputed whether the c. in c. also bound the judge.
Some, basing themselves on c. 10, X, II, 22, which gives the judge the faculty to interrogate "quoties dubitationi aliquid occurrerit", maintained the principle: "iudici numquam concluditur in causa". After the CIC there is no lack of canonists who still maintain it, especially for criminal causes. In any case, the faculty to interrogate after the conclusion must be understood as that of producing new proofs (c. 1742 § 3), which means that the aforementioned principle is to be admitted, if at all, with the limitations indicated there.