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?

  • 4
    The whole process is imbalanced in favor of the defendant for a good reason. And being a "good guy" isn't evidence. Aug 24, 2021 at 3:35
  • @GeorgeWhite Being a "good guy" could well be propensity evidence. The prosecution's right to offer this kind of evidence often hinges on whether the defendant does. If the defendant offers it in surprise, there will be little opportunity for the prosecution to offer their version. There is a good reason for that too I presume?
    – Greendrake
    Aug 24, 2021 at 8:35
  • It is much more expensive to prosecute a criminal case than to defend it, and the ethos of common law prosecutors is to have exhaustive proof on every last detail. Most trial presentations in criminal cases involve a long prosecution case (spiced with defense objections and cross-examination) and a very short defense case, although there are always exceptions.
    – ohwilleke
    Aug 24, 2021 at 20:12

2 Answers 2


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.

  • 1
    "Virtually every jurisdiction"? Strangely, New Zealand does not seem to be one of them.
    – Greendrake
    Aug 24, 2021 at 4:05
  • Disclosure of witnesses by the defense is more common than an advanced requirement of disclosure of exhibits. But, all witnesses can be "may call" witnesses, many of whom may never end up being called, so one carry make a long list of potential witnesses to bury the ones the defense really plans to call. Exceptions to pre-trial disclosure requirements are also granted more liberally in criminal practice than in civil practice.
    – ohwilleke
    Aug 24, 2021 at 20:09

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.

  • Wowowow. This is very surprising. I would love to practice in NZ.
    – bdb484
    Oct 5, 2021 at 19:03

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