Preparing evidence for opposition proceedings in the Trade Marks Office has its own set of traps for the unwary. Over the next few posts, I will highlight a few common weaknesses in TMO evidence.
Error #1: Ignoring the priority date
For most grounds of opposition, the critical date is the date of lodgement of the trade mark application. It is as at this date that the opposition must be assessed. Despite this, it remains common for parties to file evidence which only (or largely) relates to circumstances after the priority date. Such evidence is often easily attacked as being entirely irrelevant or of very low weight.
In some cases, however, post-priority date evidence can be relevant.
In Conde Nast Publications Ltd v Taylor, Burchett J said:
[I]t is a commonplace of the law of evidence that later events may cast light upon the true position at an earlier date. … [I]t is cold common sense to see actual events as capable of illuminating the probabilities already inherent in the situation from which they arose. That evidence of events since the application date is material and admissible was accepted by Gummow J in Johnson & Johnson v Kalnin  FCA 210; (1993) 26 IPR 435 at 439. As his Honour pointed out, the onus must be borne in mind, and also the difficulty in obtaining evidence of confusion or deception.
Thus, post-priority date evidence may be relevant insofar as it casts light on events as at the priority date. That will not allow a party to rely on evidence of use of a trade mark after the priority date to establish proprietorship, reputation or likelihood of confusion as at the priority date where there was no actual use before the priority date. But evidence of matters after the priority date may be relevant to support an inference of relevant trade mark use and/or a likelihood of confusion existing as at the priority date.
Another limited exception is that evidence of trade mark use after the priority date may be relevant to the discretionary factors to be determined in respect of honest concurrent use under s 44(3).
Evidence from after the relevant date should be used with caution but not necessarily avoided. It will sometimes provide the best evidence available of relevant use or confusion in the market.
 For a recent case where no weight was given to evidence from after the relevant date, see Roger Maier v Asos Plc  ATMO 7.
 For a recent discussion of some of these authorities, see The H.D. Lee Company Inc v Tracey Taylor  ATMO 49 from .
 (1998) 41 IPR 505 at 509.
 Conde Nast Publications Pty Ltd v Taylor (1998) 41 IPR 505 per Burchett J at 509; see also Johnson & Johnson v Kalnin (1993) 26 IPR 435 per Gummow J at 439.
 PB Foods v Malanda Dairyfoods Ltd (1999) 47 IPR 47 per Carr J at -.