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In patent litigation, defence teams engage in a forensic analysis of the patent in question to identify convincing arguments as to why the patent is invalid. 

Apart from conducting a thorough technical analysis, this pursuit can also involve trying to close gaps in the defence’s case through ‘left-field thinking’. Many of the more ‘inventive’ arguments never see the light of day because by the time the case gets to trial, the defence team wants to focus on their best arguments.

The decision in Southern Cross Mining Services Pty Ltd v Mickala Mining Maintenance Pty Ltd [2020] FCA 1064 is an interesting example of a defence team’s inventive thinking and sheds some light on the rarely pleaded ground of invalidity due to secret use of an invention.

Southern Cross is asserting that Mickala infringes its innovation patent in respect of a low-voltage lighting tower. The decision relates to a request by Mickala to amend its cross-claim for invalidity, so it could rely on additional particulars of invalidity. Mickala discovered an advertisement made by Southern Cross for a lighting tower published just over a year before Southern Cross filed for the innovation patent.

Innovation patents can be particularly difficult to invalidate. Firstly, they are often crafted with narrow claims targeting the alleged infringer; as a rule of thumb, the narrower the claim the more likely it is to be valid. Secondly, the standard for patentability of an innovation patent is relatively low because it only needs to be novel relative to any prior art. Therefore, if any features in the claims are not found in the prior art, the patent will most likely be valid. This differs to a standard patent application where one can argue that any missing features are ‘common general knowledge’.

Mickala alleged that the advertisement rendered the patent invalid for lack of novelty and Southern Cross did not resist the amendment to incorporate this particular claim.  However, the defence team must have been concerned that the advertisement didn’t clearly disclose all the invention’s features. Their left-field solution to this potential problem was to attempt to include an alternative argument that the advertisement was a secret use of the invention.  

“Hang-on a second”, we hear you say, “it’s not very secretive to advertise something!” Indeed, this troubled the Judge as well, who stated “it is difficult to see how the act of placing an advertisement in relation to the products in an industry journal could be regarded as having “secretly used” the invention”.

The Judge went through the relevant legal authorities and derived two broad principles related to secret use:

  1. The use had to be of a type that involved the patentee (Southern Cross) obtaining a commercial benefit which resulted in a de facto extension of the term of patent; and
  2. There had to be an intention to keep that use secret - i.e. it wasn't accidentally kept secret.

The Judge queried how Southern Cross could satisfy the requirement of obtaining a commercial benefit if they had not actually sold the product. Mickala’s answer, was that it wants to argue that the advertising put Southern Cross in a position to make sales after the priority date; sooner than it would have made those sales had the advertisements been placed on or after the priority date. The Judge indicated if Mickala pursue this argument, it was up to Mickala to find evidence supporting that contention.

Despite scepticism concerning the secret limb, the Judge was prepared to contemplate that if Mickala could show there was intentional concealment of essential features from the public in the advertisement, it could potentially satisfy the requirement for intentional secrecy.

Though Mickala’s left-field argument has not been completely ruled out, it was made clear that they must overcome several obstacles to run the argument at trial. It will be interesting to see if they are able to do so, and if successful, will extend the scope of secret use attacks.


If you have any questions or require expert advice, please don't hesitate to contact us

Author: Nick Mountford - Patent Attorney 



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