The rule in Browne v. Dunn is one that defence counsel must keep at the forefront of their minds when conducting trials.
This well-known rule stands for the proposition that if counsel is going to challenge the credibility of a witness by calling contradictory evidence the witness must be given the chance to address the contradictory evidence in cross-examination while he or she is in the witness box. (R. v. Kosowan, 2015 SKPC 8, para 6)
In R. v. Kosowan, the Saskatchewan Provincial Court was asked to make a ruling about whether the rule in Browne v. Dunn had been breached. The Crown argued that Defence Counsel did not put enough of the contradictory evidence to a witness, thereby not affording her an opportunity to explain. The Crown was seeking to recall that witness.
Quoting from R v Verney (1977), 87 CCC (3d) 363 at 376 (Ont CA), the court wrote the following:
Browne v Dunn is a rule of fairness that prevents the “ambush” of a witness by not giving him an opportunity to state his position with respect to later evidence which contradicts him on an essential matter. It is not, however, an absolute rule and counsel must not feel obliged to slog through a witnesses’s evidence-in-chief, putting him on notice of every detail that the defence does not accept. Defence counsel must be free to use his own judgment about how to cross-examine a hostile witness. Having the witness repeat in cross-examination, everything he said in chief, is rarely the tactic of choice. . . .
After reviewing the case law and the questions put to the witness by defence counsel, the court found:
 Defence counsel was not obligated to put all the details to Ms. Redman concerning the contradictory evidence he expected Ms. Zurloff to proffer. He asked her a number of times whether they had people over to the residence that night or any time in 2013 and she repeatedly responded they did not.
The court ruled there was no breach of the rule in Browne v. Dunn, and would not recall the witness.