Inventorship has been described as “one of muddiest concepts in the muddy metaphysics of the patent law" [Mueller Brass Co. v. Reading Industries, Inc., 352 F.Supp. 1357, 1372 (E.D.Pa. 1972)]. Determining inventorship is a complex issue that is undertaken on a much stricter basis than authorship of a scientific publication.
It can also be a particularly contentious issue when people are not named as inventors. Not only can this lead to alienation, but it can also lead to legal issues. For example, a patent may be invalid if incorrect inventors are intentionally named. During litigation, a defendant may also be able to identify an unnamed inventor and obtain an assignment from them, thereby qualifying as a co-owner of the patent and no longer subject to the litigation.
Since entitlement to a patented invention ultimately flows from the inventors, making a proper determination regarding inventorship is of particular importance. However, the laws concerning inventorship vary from jurisdiction to jurisdiction. Accordingly, a person may be considered an inventor in one jurisdiction, e.g., USA, but not in another, e.g., Australia.
Australian decisions concerning inventorship and the level of contribution required by a person to be considered an inventor is underdeveloped compared to the USA.
The leading decision regarding inventorship in Australia is in Polwood Pty Ltd v Foxworth Pty Ltd  FCAFC 9. According to the Court in this decision, the claims are not solely determinative of the “invention” against which inventorship is assessed, which is unlike other jurisdictions, such as the USA. Rather “[t]he invention or inventive concept of a patent or patent application should be discerned from the specification, the whole specification, including the claims. The body of the specification describes the invention and should explain the inventive concepts involved. While the claims may claim less than the whole of the invention, they represent the patentee's description of the invention sought to be protected and for which the monopoly is claimed. The claims assist in understanding the invention and the inventive concept(s) which give rise to it. There may be only one invention but it may be the subject of more than one inventive concept or inventive contribution. The invention may consist of a combination of elements. It may be that different persons contributed to that combination.” (at  emphasis added)
Ultimately, in making their decision the Court considered whether the contribution by the parties went to the “heart” of the invention or the general inventive concept, rather than each feature of the claims. The decision provides the following general guidelines for determining inventorship in Australia, including:
Identifying the nature of the invention and the ‘inventive concept’, and
Identifying the nature of the contribution to the invention, including whether:
the contribution had a material effect on the final invention,
the contribution was part of a collaborative effort,
the person contributed to the ‘conception of the solution’ to a problem solved by the invention,
the person had a general idea of what was required but did not necessarily know how to put that idea into effect, and another person did so, and
the final concept of the invention would not have materialized without the person's contribution.
The Courts consider the nature of the contribution to be the most important requirement in determining inventorship. Other considerations provided by the Australian Courts or Patent Office in determining inventorship include:
that the contribution to the invention must be material, in the sense that without this contribution the invention "would have been less" (University of Western Australia v Gray  FCAFC 116)
a question to consider is “would the invention have occurred without [the person’s] involvement (Harris v C.S.I.R.O (26 IPR 469)), and
“[a] secondary consideration is whether the person’s contribution involved a key inventive step” Upham and Commissioner of Patents; Victor and Dan Vrubel (Joined parties) (AAT No. 13418  AATA 852).
However, unlike authorship on a scientific publication, not all contributions will necessarily provide the basis for a valid inventorship claim. Whilst a person whose contribution involved no more than carrying out instructions may be included as an author on a publication, to be named as a joint inventor on a patent, the Courts and Patent Office have provided the following guidance:
“where one party takes an initial step leading from the problem toward the ultimate solution and their work is taken up and finalized by another, both may be considered to have jointly contributed to the invention” (Pimmcoy Pty Ltd v. Barry Charles Teer  APO 37),
joint inventorship occurs where one party has a general idea of what is required to solve a problem, but requires the input of another party to give effect to those ideas (Dominic Victor Costa v. GR & IE Daking Pty Ltd  APO 23), and
“joint inventorship is to be determined by the quality of each person’s contribution to the invention, not the quantity of this contribution” (Polwood Pty Ltd v Foxworth Pty Ltd  FCAFC 9).
The position in the USA is far more developed than in Australia, largely due to their previous "first to invent" patent system, which often required not only identification of an inventor, but also often establishing a date of the invention. Under USA practice, the inventive process involves designing or “conceiving” the invention, and then creating or producing the conceived invention, otherwise known as “reduction to practice”. However, identification of inventors focuses almost entirely on determining who conceived the invention.
Conception is defined as “the formation in the mind of the inventor of a definite and permanent idea of the complete and operative idea as it is hereafter to be applied in practice” (Townsend v Smith, 36 F.2d 292, 295, 4 USPQ 269, 271 (CCPA 1930)). Moreover, conception is only complete when “the invention is made sufficiently clear to enable one skilled in the art to reduce it to practice without the exercise of extensive experimentation or the exercise of inventive skill” (Hiatt v. Zeigler, 179 USPQ 757, 763 (Bd. Pat. Inter. 1973)). Of course, more than one person can contribute to the conception of the invention. The contributions of the joint inventors need not be equal. Nor do the contributions have to have occurred at the same time (Monsanto & Co. v. Kamp 154 USPQ 259). However, the combined contributions must permit the skilled person to reduce the invention as ultimately claimed in a granted patent to practice without the exercise of inventive skill.
Unlike Australia, under USA practice the analysis of inventorship is performed on a claim-by-claim basis and must consider every feature or limitation of the claimed invention.
When it comes to joint invention, USA Courts have provided much guidance, including:
“For each person to be joint inventors… there must be some element of joint behavior, such as collaboration or working under common direction, one inventor seeing a relevant report and building upon it or hearing another’s suggestion at a meeting” (Kimberly-Clark Corp v Proctor & Gamble Distrib Co, Inc 973 F.2d 911 (Fed Cir 1992)).
“[E]ach inventor need not have their own contemporaneous picture of the final claimed invention in order to qualify as joint inventors… (‘One need not alone conceive of the entire invention, for this would obviate the concept of joint invention’)” (Vanderbilt University v Icos Corporation Fed Cir 2010 citing Fina Oil & Chem Co v Ewen, 123 F.3d 1466, 1473 (Fed. Cir. 1997)).
“Each inventor must contribute to the joint arrival at a definite and permanent idea of the invention as it will be used in practice” (Burroughs Wellcome v Barr Labs Inc 40 F.3d 1223, 1229 (Fed Cir 1994)).
“The interplay between conception and collaboration requires that each co-inventor engage with the other co-inventors to contribute to a joint conception” and “a group of inventors must collaborate and work together to collectively have a definite and permanent idea of the complete invention” (Vanderbilt University v Icos Corporation, 601 F.3d 1297 (Fed Cir 2010)).
When it comes to chemical/biological inventions, the USA Courts have also provided guidance as to what is required to conceive of an invention, for example, “conception does not occur unless one has a mental picture of the structure of the chemical… or whatever characteristics sufficiently distinguish it. It is not sufficient to define it solely by its biological property…” (Amgen Inc v Chugai Pharmaceutical Co, 927 F.2d 1200 (Fed Cir 1991). However, the Courts have also warned
"that a putative inventor who envisioned the structure of a novel genus of chemical compounds and contributes the method of making that genus contributes to the conception of that genus. This holding does not mean that such an inventor necessarily has a right to claim inventorship of all species within that genus which are discovered in the future” (Falana v Kent State University, 669 F.3d 1349 (Fed Cir 2012)).
While there have been few decisions concerning inventorship in Australia, the decisions to date suggest some different considerations to those used in the USA. In particular, the focus on the underlying “heart(s)” of the invention(s) as described in the application in Australia is different to the claim-by-claim and feature-by-feature analysis in the USA. Whether or not this difference will ultimately result in different parties being named as inventors in patents in Australia and the USA remains to be seen. However, it is conceivable that a person may be named as an inventor in Australia based on contribution of an underlying inventive concept that is not specifically claimed and that person does not qualify for inventorship in the USA.