What is the difference between live testimony and pre-trial deposition?

Live testimony remains preferable to pre-trial deposition for a number of reasons. Some of these reasons were enumerated by Justice Harris in Byer v. Mills, 2011 BCSC 158 at Appendix A, and they include: a) Where the deposition is of a defence witness, the defence evidence is taken before the plaintiff has led any evidence at all. This complicates what is otherwise an orderly framework for the receipt of evidence by the court. For example, taking defence evidence first gives rise to the risk that the defence evidence is not properly responsive to the plaintiff’s case. b) A deposition complicates the process for objections. At a deposition, the judge is unable to rule on objections in real time, risking a witness spending time answering improper questions. Also, if a question is objectionable but subject to being reframed on the instruction of the court, this opportunity is lost at a deposition. c) The trial judge has an important role to play in controlling the trial process, including in some cases controlling the conduct of a cross-examination. Taking evidence by deposition eliminates the opportunity for the court to play this role.