Defendant's right to surprise prosecution at trial

Question

Common law disclosure obligations between prosecutors and defendants appear to be imbalanced:

• prosecutors basically have to disclose everything they have on defendants
• defendants have to disclose only alibi and any expert witnesses (and also some extra stuff where co-defendants are involved, but let's consider only single-defendant cases for simplicity)

That, on the face of it, allows defendants to surprise prosecution at the trial with any witnesses/evidence that are neither alibi nor experts.

Consider this scenario: Dave is on trial. At the time of the alleged crime, Wendy was his wife, but no longer now, so she can be compelled to testify. Peter (prosecutor) approaches her to see if she knows anything against Dave, but she won't talk. At the trial, the defence just calls her out of the blue and she testifies what good guy Dave was and how he could not possibly commit the crime etc.

Is that what prosecution just has to be alert to and fly by the seat of their pants, e.g. no way to either compel the defence to disclose the witness in advance, or rule it inadmissible?

Similarly, Dave could keep secret his intention to give evidence right till the end of the trial, right?

Answer 1

Although there have long been requirements to disclose certain types of defenses -- alibi, insanity, etc. -- common law jurisdictions have more recently moved in the direction of greater disclosure obligations for the criminal defendant.

Virtually every jurisdiction now requires the defendant to disclose his witnesses and his evidence to the prosecution at some point before the trial, at least if the defendant has made discovery demands of the prosecution.

For more information on common-law discovery rules, see here.

Answer 2

new-zealand

Is that what prosecution just has to be alert to and fly by the seat of their pants, e.g. no way to either compel the defence to disclose the witness in advance, or rule it inadmissible?

Pretty much.

Defendants only have to disclose in advance any alibi and any expert witnesses. Everything else will be surprise to the prosecution at trial.

Specifically, defendants are allowed to first present their version of events right in the witness box — after hearing all the case against them and talking to their lawyers of what to say, if anything.

Prosecution still may be allowed to call any witnesses in rebuttal, the contents of which must have been disclosed to the defendant prior to the trial.