I do think that it seems appropriate to create a perjury offence or similar, while most instances of it would probably be caught by fraud, I don't think that means there shouldn't be a more specific offence to recognise a particularly harmful category of conduct, at the very least it allows the scope for differing punishment (though, at the moment, fraud has no specific restriction on punishment).
In terms of the proposed definition, I think there are some issues that require consideration.
First, in relation to testimony, the mental requirement proposed is dishonesty. This isn't a standard currently in use in the Legal Code and I wonder whether there is a risk of that creating some confusion when it comes to be used, at least initially. Intentional deception, which is used in the current fraud offence, has already been considered in some detail by the Court and is used for another means of committing the proposed offence, so I wonder whether it may be more appropriate to use that phrasing for all elements of the proposed offence. That would avoid potential confusion over the meaning before the Court makes a determination and would also avoid having either several standards all meaning the same thing (which is an oddity currently existing with wilful and intentional) or two subtly different standards when it seems really the standard should be the same between fraud and perjury.
Second, in relation to documentary evidence, the current offence is simply the wilful provision of digitally altered imagery. As noted by Dreadton, this may leave scope for some types of evidence to escape the scope of the offence despite being of essentially the same false nature as others. But also, I think it is overly inclusive, as there may be times (notably with a prosecution for fraud) when it may be appropriate for altered evidence to be willfully exhibited by the prosecution in order to prove an offence but without an intention to deceive the Court as to the fact of the evidence being altered. I think, therefore, that it would make sense to have the definition as being "intentionally deceptive provision of altered evidence" or similar.
Third, briefs are caught by the proposed offence. I am not sure my view on this in particular. I can appreciate why it might be included, but it does seem to me that there may be reasons why context of a criminal trial requires the greater protection of a specific offence while requests for review don't. One such reason is that requests for review are, by and large, without any dispute as to the factual basis of them and so, in general, briefs shouldn't be deceptive in any material way as they should usually be focused on the law rather than facts, unlike evidence in a trial which ought to be the reverse. Another, though linked, reason is that requests for review don't really have clear standards around evidence and findings of fact, whereas the criminal standards are fairly specific and stringent, such that there doesn't seem, to my mind, to be as much of a risk; that is, the Court in a criminal trial must, if a reasonable doubt is created by misleading evidence, acquit the Defendant, while in a request for review the same standard of proof does not apply and the Court would appear to be able to conclude on the basis of what appears more likely even if there is information pointing away from that conclusion that could in a criminal trial compel an acquittal.
Fourth, as noted by Darcania, there is no provision for specific punishment in the Penal Code. This leaves the scope of punishment wholly to the Court. I have raised this issue in the past in connection with the fraud and election fraud offences (and hopefully will one day get around to resolving it) and it would not be unique to this offence, but I don't think that it is generally appropriate for such wide discretion on punishment to be left to the Court and it seems to me that some specific provision should be included for the new offence.
