Persons who are arrested or detained have a constitutional right to counsel.

Defence counsel would most routinely appear after charges have been laid and make court appearances with the individual charged. The Canadian Charter of Rights and Freedoms allows any individual who is detained as part of an investigation to immediately contact counsel and seek legal advice from such counsel pre-charge.

The right to counsel protects the right of accused people to remain silent and not incriminate themselves, the right to be secure against unreasonable search and seizure, the right to make full answer and defence, and the right to a fair trial. The right to counsel is the means by which the innocent are protected from wrongful conviction.

Defence counsel ensure that full disclosure is provided by the Crown; that all evidence bearing on the accused's case is disclosed or produced; that all legal issues bearing on the accused's case are fully explored and properly adjudicated; that, in particular, all evidence tendered by the Crown was collected in accordance with constitutional standards; that all evidence supporting the accused's case is tendered at trial; that Crown witnesses are cross-examined and weaknesses in the Crown case are explored; that an accused is convicted only when the Crown has satisfied its constitutional burden of proving guilt beyond a reasonable doubt, on the basis of all of the evidence; that, where an accused is convicted, the penalty is proportionate to the gravity of the offence and to the degree of culpability of the accused; that all options are explored for rehabilitation and reintegration of the accused, consistent with community safety; and that apparent errors made in trials are properly reviewed on appeal.

Defence counsel is professionally bound to advance all arguments ethically permitted on behalf of the accused, to ensure that the accused is convicted only if the government can properly establish guilt.