An admission is evidence presented in trial that consists of either a written or oral statement by the Accused admitting some fact made to a witness. This form of admission is a categorical exception to the hearsay rule of inadmissibility. This applies regardless of whether the admission is exculpatory or inculpatory. The main determiner for admissibility is the discretionary balance of probative value and prejudicial effect.
Third Party Admissions
A third party admission is evidence given from a non-accused witness with respect to a statement given by the accused at some time in the past. The two main forms of third party admissions are adoptive admissions and vicarious admissions.
An adoptive admission is where the admission arises by the Accused's adoption of a 3rd party's statement. The adoption can be made by words, actions, or demeanour. The adoption is only to the extent the Accused accepts the statement by words, conduct or demeanour.
This admission can apply where the accused makes a statement, action or is silent in the face of a criminal accusation. The weight depends on whether the accused had a duty to speak and was expected to say something. 
This does not apply where the accused fails to reply to accusations under caution.
A vicarious admission is one where an admission of the Accused is relayed by a third party. The admission can be by words, actions, or demeanour. This form of admission is often taken from a co-conspirator of the Accused.
Statements that were made in the presence of the accused are not admissible unless the accused assents to them by words, conduct, action or demeanour.
- R v Emele (1940), 1940 CanLII 203 (SK CA), 74 CCC 76 (SKCA)
- R v Sigmund (1968), 1 CCC 92 (BCCA)(*no link)
- R v Chambers, 1990 CanLII 47 (SCC),  2 SCR 1293
R v Cripps  3 CCC 323 (BCCA)(*no link)
R v Thomas, 2013 ONSC 1640 (CanLII) at para 11
R v Taggert  O.J. No. 1273 (O.C.A.)(*no link) at para 8
R v Pleich, (1980) 55 CCC (2d) 13 (O.C.A.)(*no link) at para 68
R v Dubois, (1986) 27 CCC (3d) 325 (O.C.A.)(*no link) at para 47
Admissions to Undercover
An undercover officer posing as an inmate within a prison may only listen and not actively seek a confession.
An undercover officer who is in contact with an accused out of custody, such as during a "Mr. Big" operation, may listen and activity attempt to elicit confessions.
Admissions During "Mr. Big" Operations
A Mr. Big operation is where undercover officers lure a suspect into joining a fictitious criminal organization culminating in an interview where the officers seek to elicit a confession to the offence under investigation before the suspect can be permitted to join the criminal organization.
Where the accused gives a statement in the course of a "Mr. Big" operation the statement is presumptively inadmissible.
This presumption can be overcome where the Crown can establish on a balance of probabilities that the "probative value of the confession outweighs its prejudicial effect".
R v Hart, 2014 SCC 52 (CanLII) at paras 1 to 2, 10
Hart, ibid. at para 10 ("where the state recruits an accused into a fictitious criminal organization of its own making and seeks to elicit a confession from him, any confession made by the accused to the state during the operation should be treated as presumptively inadmissible")
- Hart, ibid. at para 85
Admission by Co-accused
It is generally well established that an accused's statement is admissible only against the person making making it. It is not admissible against a co-accused.
It is for this reason that co-accused can have separate trials.
Guilty Plea of Co-Accused
A guilty plea of a co-accused or uncharged accomplice will usually no relevancy to the issue of guilt of the accused. The prejudicial effect of the evidence will often outweigh any probative value of such evidence.However, where it is permissible, such as for the purpose of credibility assessment, it should usually be accompanied by instructions warning of its use.
R v Ward, 2011 NSCA 78 (CanLII) paras 28 to 40
R v BC,
McFall v The Queen,  1 SCR 321, 1979 CanLII 176
R v Starr, 2000 SCC 40 (CanLII) at para 217
R v Kelawon 2006 SCC 96 (CanLII) at para 96
- Guimond v The Queen,  1 SCR 960, 1979 CanLII 204
R v Berry, 1957 CanLII 115 (ON CA),  O.R. 249 (C.A.)
R v Buxbaum (1989), 33 O.A.C. 1 (C.A.), leave to S.C.C. refused
R v Lessard (1979), 50 C.C.C. (2d) 175 (Que. C.A.)
R v Caesar, 2016 ONCA 599 (CanLII), 350 O.A.C. 352
R v Berry, 2017 ONCA 17 (CanLII) at para 35
Berry, ibid. at para 36