What makes a ‘strong’ patent?

The article below is adapted from a presentation of the same title by David Nowak to a Legalwise Education webinar on 31 May 2022.

The concept of a ‘strong’ patent is difficult to define. As with many things in patent law the answer is “it depends”.  Mostly it depends on what the patentee wants the patent to achieve. A patent which does not support the business goals of the patentee is not strong. 

A “strong” patent is often seen as one that is enforceable – a patent under which infringement can be found and which can withstand a test of validity.  However, this ignores that, in order to get a patent, one needs to go through the application process.  Considerations during the application process should not differ markedly from those of validity.  However, there are certain areas where they may differ.  In order to capture these difference, for present purposes, a strong patent is one that survives the application and examination process, can withstand challenges to validity and has sufficient breadth to be infringed.

Key factors for a strong patent, such as patentable subject matter, novelty and inventive step are inherent to the invention and are thus often beyond the control of the patentee or IP professional.  In this paper we consider factors which are within the control of the patentee or IP professional, and may assist to strengthen a patent.

The priority application

The best approach to a strong patent is to get things right from the start.  While patent systems usually allow opportunities to correct errors or add information, the provisions are often not universal across all jurisdictions. 

Conventionally the first step in applying for a patent is to file a priority application.  In most cases subject matter is able to be added between filing of the priority application and filing of the eventual ‘complete’ specification.  For this reason the specification accompanying the priority application is often a briefer or less complete description of the invention, with additional details expected to be included at a later date.

However, the addition of subject matter between priority application and complete specification should be avoided if possible.  In many jurisdictions around the world the standard required for a claim to be entitled to claim priority is akin to the requirement for internal support for the claim, although there are significant differences between the grounds1. Thus in order to claim priority the description in the priority application should be complete as possible.

Avoiding a claim which is not entitled to the earliest priority date can avoid issues with intermediate disclosures.  One particular issue which has arisen in recent years relates to whether different parts of a claim can be entitled to different priority dates (i.e. partial priority and the “poisonous divisional” issue).  Although this issue has been solved in Europe2 but have yet to be satisfactorily resolved elsewhere, for example in Australia3 and New Zealand4.

It is also advisable to have conducted a prior art search and assessment prior to the drafting the priority application.  Quite apart from informing whether it is a good idea to proceed with the patent, it allows the specification and the invention to be defined in the knowledge of and avoiding the prior art.  A clear formulation of the invention will also assist in other areas such as defining the inventors (see further below).

Ideally the priority specification will include claims and in particular claims phrased as a multiple claim dependencies.  Whilst there is no requirement that a priority application includes claims, by including claims having multiple claim dependencies the possibility that the specification that particular combinations are not disclosed (and thus a claim is not entitled to a priority date) may be avoided5.

Inventorship and Ownership

It is important to identify the inventors and owners prior to filing the priority application.  As entitlement to a patent starts with the inventors, the actual devisors of the invention6, it is important that these be determined as early as possible.  In some cases it may be a ground of invalidity where the inventors are not correctly declared7 although in most cases the inventorship can be corrected8.  The requirements for what makes an inventor may differ between jurisdiction.  The test in the United States tends to focus on the claimed invention whereas in New Zealand, Australia and the United Kingdom the inventor is that of the inventive concept as determined from the whole specification.  In general the tests for who is an inventor focus on the conception of the invention and the extent to which reduction to practice was routine9.

The chain of title which extends from those inventors is also relevant, and it is necessary to ensure that the relevant party (assignee) has the relevant rights at the appropriate time.  Not only is it important that the patent is granted to the correct party10, but it may also be crucial that rights are assigned to the correct party at the correct time, especially the right to claim priority11.  Thus it is important that the chain of ownership be correct throughout the application process and throughout the lifetime of the patent.

The ‘Complete’ Specification

The Description

It should come as no surprise that description and support requirements are a growing area in which patents are found invalid.  Raising the standard of written support was a key feature of both the Australian Raising the Bar Act12 and the New Zealand Patents Act 201313.  However, an increase in the requirements for written description was already apparent in other jurisdictions, in particular the EPO and the UK14.  Thus particular attention should be paid to the extent of the description necessary for the desired claims. 

Include data in the ‘complete’ specification

Although there is no specific requirement to ‘exemplify’ an invention, in practice certain inventions will almost always require some form of experimental data, whether to demonstrate that the invention is sufficiently described15, and/or to show an inventive step16.  A failure to provide data can often result in a disclosure/inventive step squeeze, where on the one hand the Patentee is obliged to argue that either the invention is adequately disclosed to the person skilled in the art by reference to the common general knowledge, in which case it is obvious, or, on the other hand the invention requires more than just the common general knowledge to be put into effect, thus failing for written description.

Post-filing evidence can be included in some circumstances17, although the exact extent of this remains uncertain18.  In terms of having a ‘strong’ patent it remains preferable to include the evidence in the specification. 

Best method

A requirement unique to Australian and New Zealand law is the requirement for the best method.  This ground has grown teeth in the last few years in Australia19.  An important point to note is that the requirement is to disclose the best method known to the patentee at the time of filing the ‘complete’ specification.  Accordingly this is one area where the complete specification should differ from that accompanying the priority application, if there have been advances to the best method in the ensuing period.  It is also worth noting that in Australia, the relevant date for determining the best method for a divisional application is the date of filing of the divisional application20.

Don’t make promises the invention can’t keep

The use of object clauses in a specification is a commonly used device to shape any assessment as to where the utility of an invention lies.  However, the drafting (and amendment) of such an object clause should be undertaken with care.  Certain jurisdictions, most notably Australia21 and possibly New Zealand22 provide for a ground of invalidity that the invention does not meet the stated promise in the specification (the so-called promise doctrine).  Thus it is important that the claimed invention satisfies the stated object of the invention.  If multiple objects are recited they should be recited in the alternative only23 and it may be of use to include a phrase along the lines “or at the very least provide the public with a useful choice”24.

Micro-organism deposits

Where an invention is a micro-organism, or the invention involves the use of a microorganism not reasonably available, it is in many jurisdictions obligatory to file a micro-organism deposit25.  Although this requirement has now been legislated for, it was recognised even under the ‘old’ Patents Act (UK) 1949 that some inventions could best be described by a deposit26

The timing for the filing of this deposit can differ from jurisdiction to jurisdiction, but at least in some jurisdictions the deposit must be made at the time of filing of the priority application27.   Thus it is submitted that if an invention relates to a micro-organism, a deposit should be filed at the time of filing the priority application.  Reference to the deposit (depositary institution and number) should also be included in the ‘complete’ specification to avoid later issues.  There are other requirements of disclosure to various Patent Offices regarding deposits of which Applicants should be aware28.

On the basis that in may not just be micro-organisms which are best described by way of a deposit, consideration should also be given to filing deposits for non-micro-organism related inventions, for example hybridomas or other eukaryotic cell lines.

Sequence listings

Sequence listings providing an amino acid or nucleotide sequence are now a common feature of patent applications.  It is necessary to be aware of the requirements to provide sequence listings in particular formats29.  It is preferable that, in addition to providing the sequence listing in the required searchable format, the sequences should be included in the specification proper.  The legislation of some jurisdictions does not explicitly address the status of a separate sequence listing as part of the disclosure30.  By including the sequence as part of the specification, any argument regarding adequacy of disclosure in which the separate sequence listing is rendered moot. 

The claims

The claims are always going to be a key consideration in framing a ‘strong’ patent since they define both the scope of the monopoly and the invention which is valid (or not). 

Draft for literal infringement

The extent to which infringement can depart from the written scope of the claims differs depending on jurisdictions31, but the claims should still be framed with best endeavours to catch any infringement within the literal meaning.

Consider who will infringe the claim

When reviewing a claim consideration, should be taken to who will infringe the claim.  Where a claim is framed as a process or method claim, it should be considered whether all of the steps in the method will be conducted by a single entity.  Although most patent jurisdictions now have provisions relating to contributory or secondary infringement32, these provisions still generally require a primary infringer, thus not covering a situation where entity A performs step 1 and entity B performs step 233

Consider damages/account of profits when drafting claims

Consideration should also be given to whether including particular categories of claim could simplify or increase any award of damages or account of profits.  Damages for infringing a claim relating to a component of a device may be difficult to quantify if the component is not sold separately, whereas if it is possible to frame a claim to the device having that component, then damages easier to quantify.

Have appropriately drafted claims at publication

Although it is generally not possible to sue for infringement until after grant, the power of the claims post publication should not be ignored.  In most jurisdictions some rights attach to the claims post-publication34. Thus an appropriate set of claims should be present at publication and maintained through prosecution.

Draft claims with potential priority issues in mind

If there is a difference in subject matter between the priority document(s) and ‘complete’ specification, claims should be drafted with that in mind35.  It is advisable to have a claim or claims which are clearly entitled to the earliest priority date in case broader claims are found to be not entitled to that priority date.  In jurisdictions where partial priority (discussed above) may not be available, it is advisable to be careful that multiple claim dependencies do not inadvertently create a claim having multiple priority dates.

Multiple claim dependencies

Multiple claim dependencies may be of value as providing for innumerably fall back positions in jurisdictions where they are allowed or are not too expensive.

Omnibus claims

Most countries have now stopped allowing omnibus claims.  However, where such claims are still allowed (primarily New Zealand), including the claims may have value.  Omnibus claims have been found to both be the last claim standing after validity challenges36, the only claim which was infringed37, or an aid to construction of the main claim38.  Thus it is submitted that these claims may be a useful addition to a granted patent.

Patent Term Extensions/Supplementary Protection Certificates

In fields where Patent Term Extensions or Supplementary Protection Certificates may be available, it is advisable to consider what is claimed.  Where there is the possibility that the claims encompass more than one product, it may even be advisable to file separate applications (e.g. by way of a divisional application) to each product in order to avoid missing out on a term extension39.

Other Factors

Make post-acceptance/grant amendments expeditiously

Frequently a new ground of invalidity arises after acceptance which necessitates an amendment.  In these circumstances, it should be remembered that allowing an amendment after acceptance is usually at the discretion of the Patent Office or Court.  Delay in making the request for amendment can be a significant factor in the Court or Office declining to exercise that discretion40. Thus it is important for Patentees and their representatives to keep abreast of any potential grounds of invalidity and to assess whether changes are required in an expeditious manner.

Don’t miss deadlines

While obvious, it is important to note that deadlines should not be missed, especially those associated with filing a specification.  In many cases these can be rectified41 but different jurisdictions may take a very different approach42.  In other cases, while the failure to meet a deadline may not be able to be rectified, missing the deadline may allow rights to potential infringers in the interim43.

Consider your filing strategy carefully

Your filing strategy should not create grounds of invalidity.  This means considering issues such as ‘whole of contents’ novelty44 and first application in a convention country45 when choosing not to proceed with applications.


The strength or weakness of a patent usually depends on factors such as subject matter, novelty and inventive step which are to some extent outside the control of the Patentee or IP professional.  However, as highlighted here, there are some steps that the Patentee or IP professional can take to strengthen a patent outside of these core areas.  The suggestions contained herein are by no means exhaustive, nor will they apply in every situation, but may serve as useful prompts.

 David Nowak - 5 July 2022



1. See for example, the EPO enlarged Board of Appeal in G2/98: “a claim in a European patent application in accordance with Article 88 EPC is to be acknowledged only if the person skilled in the art can derive the subject-matter of the claim directly and unambiguously, using common general knowledge, from the previous application as a whole”; Patents Act (NZ) 2013, ss 58-60 “supported by the matter disclosed”; Patents Act (Aus) 1990. S43(2A) “in a manner that is clear enough and complete enough for the invention to be performed by the person skilled in the relevant art”.

2. See the Enlarged Board of Appeal Decision in G1/15.

3. AstraZeneca AB v Apotex [2014] FCAFC 199 which allowed partial priority only where the claim is expressed as alternatives.

4. Patents Act 2013, ss 58-60, also the discussion regarding multiple priorities in “Intellectual Property Laws Amendment Bill – Patents Act 2013, Trade Marks Act 2002, Designs Act 1953” MBIE discussion paper, May 2019, available here.

5. G2/98 (supra) is interpreted in a manner largely equivalent to Article 123 raising intermediate generalisation issues, see the EPO examination guidelines, here.

6. See e.g. Patents Act (NZ) 2013, ss 5 and 22,Stephen L. Thaler [2022] NZIPOPAT 2 (31 January 2022); Patents Act (AU) 1990 s15; and 35 U.S.C. §§ 101, 111, and 116; 1990.

7. See for example in the United States, Jamesbury Corp. v. United States (518 F.2d 1384, 1395) (Ct. Cl. 1975).

8. See e.g. C.R. Bard, Inc. v. M3 Systems, Inc. (157 F.3d 1340, 1353) (Fed. Cir. 1998).

9. For a recent discussion of inventorship and entitlement in Australia, see Vehicle Monitoring Systems Ptd Ltd v SARB Management Group Pty Ltd [2021] FCAFC 224; for a discussion of inventorship in the context of New Zealand law see Finch et al here; for a discussion of inventorship in the United States see Konski et al Cold Spring Harb Perspect Med. 2015 Nov; 5(11): a020859 here.

10. ee for example Patents Act (NZ) 2013, s22.

11. See for example, in the EPO, the decision of the Board of Appeal in T 844/18, whereby the priority claim was found invalid as not all of the applicants for the originating priority application had assigned their rights at the time of filing.

12. IP Laws Amendment (Raising the Bar) Act 2012.

13. See the explanatory memorandum for each.  The ‘old’ standards of describing an embodiment within the scope of the claims, and fair basis, were, it must be said, very low.

14. See for example in the UK in Biogen Inc v Medeva plc [1997] RPC 1; Generics (UK) Limited v H Lundbeck A/S [2008] EWCA Civ 311, [2008] RPC 19 at [27].

15. See for example in the context of a second medical use type invention in the UK in Warner-Lambert Company LLC v Generics (UK) Ltd t/a Mylan and another [2018] UKSC 56.

16.  Enlarged Board of Appeal in T93992 AGREVO/Triazoles.

17. Warner-Lambert Company LLC v Generics (UK) Ltd Ibid.

18. See the questions referred to the Enlarged Board of Appeal, G2/21.

19. See for example in Les Laboratoires Servier v Apotex Pty Ltd [2016] FCAFC 27, BlueScope v Dongkuk (No 2) [2019] FCA 2117, and Dometic Australia Pty Ltd v Houghton Leisure Products Pty Ltd [2018] FCA 1573.

20. Dometic Australia Pty Ltd v Houghton Leisure Products Pty Ltd (Ibid), this would not apply in New Zealand due to the differences in the status given a divisional application.

21. See for example ESCO Corporation v Ronneby Road Pty Ltd [2018] FCAFC 46.

22. The effect of the insertion of section 10 of the Patents Act 2013 on the requirement for usefulness remains uncertain.

23. To avoid the possibility of a finding as found in the Federal Court in Ronneby Road Pty Ltd v ESCO Corporation [2016] FCA 588, overturned ESCO Corporation v Ronneby Road Pty Ltd (supra).

24. For a discussion as to the use of this phrase see here.

25. See for example Patents Act (AU) 1990 Sections 6, 41(1A), 41(1) - (3) and 43(2B); Patents Regulations, Regulations 1.5(1) - (4) and 3.12(5); Patents Act (NZ) 2013 ss 39 and 42-45.

26. American Cyanamid Company (Dann's) Patent [1971] R.P.C. 425.

27. See for example in Europe, Rule 31(1)(a) EPC.

28. A list of the requirements for signatories of the Budapest Treaty can be found here (no longer available).

29. WIPO will introduce and require a new sequence listing standard, ST.26 from 1 July 2022 see here.

30. For example New Zealand.

31. For example the United States, Japan and Great Britain all apply a doctrine of equivalents, whereas Australia and New Zealand still apply a stricter “purposive interpretation” test.

32. See for example Patents Act (NZ) 2013, s141, Patents Act (AU) 1990.

33. The concept of joint tortfeasorship may assist but it is better to frame the claims to have a single infringer if possible.

34. See for example in NZ in the Patents Act 2013, s81.

35. See the discussion regarding ‘partial priority’ above.

36. Raleigh Cycle Co. Ltd. v H Miller and Co. Ltd. (1948) 65 RPC 141.

37. Rotocrop International Ltd v Genbourne Ltd [1982] FSR 241.

38. Hammar Maskin AB & Ors v Steelbro New Zealand Limited [2010] NZCA 83 at [65]-[67].

39. See for example in Australia Merck Sharp & Dohme Corp. v Sandoz Pty Ltd [2022] FCAFC 40.

40. For factors that may be considered in exercising the discretion see Smith Kline & French Laboratories Limited v Evans Medical Limited [1989] 1 FSR 561; for an example of the Court declining to allow amendment in Australia see BlueScope v Dongkuk (No 2) [2019] FCA 2117.

41. See for example Marley New Zealand Limited [2021] NZIPOPAT 1 (24 March 2021) where an extension of time for filing a complete specification was allowed.

42. See for example the different standards applied to restoration of priority claim in different jurisdictions as highlighted, for example by the EPO Board of Appeal in J14/21.

43. See for example in the context of restoration in New Zealand, Patents Act 2013, s124(2) and Patents Regulations 2014, r 115.

44. See for example Patents Act 2013, s8(2).

45. See for example Patents Act 2013, s55.

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