The doctrine of "functus officio" (Latin for “having performed his or her office”) determines when the judge no longer has authority or competence over a proceeding they have previously dealt with because their duties are fully accomplished.
A judge has jurisdiction over an outstanding charge up to the point where the charge has been resolved by way of a stay, withdraw, dismissal, acquittal, or sentencing. The doctrine of functus officio refers to the principle that a court no longer has jurisdiction to change any decisions once a charge has reached its ultimate conclusion.
In the case of a conviction being entered, the judicial role of the judge ends once a sentence has been imposed. After that any changes to or issuance of orders are "ministerial or administrative act[s]".
This common law rule states that the final judgement of a court cannot be reopened.  The power to review a decision is transferred by the Judicature Act to the appellate division.
This rule only applies to judgments that have been drawn up, issued and entered.
The purpose of the doctrine is to provide finality of court judgments to allow for potential review by an appellate level of court.
A court has limited power to reconsider or vary judgments so long as it is not functus.
R v E.(J.), 2013 ONCJ 247 (CanLII) at para 17
Chandler v Alberta association of architects, 1989 CanLII 41 (SCC),  2 SCR 848 at para 19
R v Melvin, 2005 NSSC 368 (CanLII), at para 13
R v Fuller,  3 CCC 349 (Man. C.A.)(*no CanLII links)
originates from Re St. Nazaire Co. (1879), 12 Ch. D. 88
Chandler v Alberta association of architects, supra
R v Adams, 1995 CanLII 56 (SCC),  4 SCR 707 at para 29
Doucet-Boudreau v Nova Scotia (Minister of Education), 2003 SCC 62 (CanLII),  3 SCR 3 at para 79
- R v Adams, at para 29
Timing of Conclusion
It is said that a court is functus if and only if "the duties and functions of the [court’s] original commission have been fully accomplished"
A trial judge sitting without a jury is functus officio only after he has imposed his sentence.
In a judge-alone case, the judge becomes functus when he "endorses the indictment".
An intermittent jail sentence cannot be varied by the sentencing court to a non-intermittent. There is some authority suggesting that the court may vary the entry and exit times of the intermittent sentence based on the power of the court to control its own process.
A judge is not fuctus simply by reason that he has given a decision for conviction. In certain circumstances the judge may hear further evidence on an issue raised in trial after finding of guilt and has the option to reopen the case.
An error made in making a SOIRA order of an illegal duration cannot be amended unless it was the judge's manifest intention to make an order of a lawful duration in which case the court has inherent jurisdiction to amend.
A court will not be functus up until the Court enters an official judgement into the rolls.
Where a mandatory order such as a DNA or 109 Weapons order was omitted there is some suggestion that the court may go back and remedy the omission.
- Jacobs Catalytic Ltd. vs International Brotherhood of Electrical Workers, Local #353 2009 ONCA 749; 312 DLR (4th) 250 at para 60
- R v MacDonald 1991 CanLII 2424 (NS CA), (1991), 107 N.S.R. (2d) 374
R v Malicia, 2006 CanLII 31804 (ON CA) at para 16
R v Germaine (1980) 39 NSR (2d) 177(*no CanLII links)
at para 5 - no jurisdiction to make intermittent to non-intermittent because not in text of 732
R v Jules  BCJ 1605 (*no CanLII links)
R v EK, 2012 BCPC 132 (CanLII)
c.f. R v Crocker, 2012 CanLII 42379 (NL PC)
- e.g. R v Boyne, 2012 SKCA 124 (CanLII) - judge heard disclosure arguments after conviction at trial
R v DM, 2013 ONSC 141 (CanLII),  O.J. No. 83 (S.C.J.)
R v E(J), 2013 ONCJ 247 (CanLII)
- R v Villeda, 2010 ABCA 410 (CanLII)
- e.g. R v Field, 2013 NSPC 92 (CanLII)
There are exceptions to this rule. The court may still interfere with a prior decision where:
- where there had been a slip in drawing it up, and,
- where there was an error in expressing the manifest intention of the court
A error on the notation of a jury verdict by a judge may be corrected if spotted shortly after the verdict is rendered.
However where the error correction is "in reality" a "reconsideration of the verdict (or sentence}" then it is prohibited. It is also in error "where issues of unfairness or injustice to the accused or reasonable apprehension of bias arise.”
The judge may make corrections to warrants of committal as an administrative act through the clerk of the court.
- Chandler v Alberta association of architects, 1989 CanLII 41 (SCC),  2 SCR 848
- R v Burke, 2002 SCC 55 (CanLII),  2 SCR 857
R v Krouglov, 2017 ONCA 197 (CanLII), per Epstein JA, at para 40
Krouglov, ibid. at para 40
R v Melvin, 2005 NSSC 368 (CanLII) at para 14
Ewing v Warden of Mission Institution (1994), 1994 CanLII 2390 (BC CA), 92 CCC (3d) 484 - regarding warrants of committal