Retrospective - How Much is 'Substantial'?

An essential component of copyright infringement in all of the common law is that the infringement, be it copying or other restricted acts, has to be done in relation to the work as a whole or a 'substantial' part of that work (Australia, UK, and Canada). The former is more than self-explanatory; however the latter has always been an abstract concept, as what can be deemed to be a 'substantial' amount can be anything between 99% of the work or a fraction of it. Due to this ambiguity the duty to define what a 'substantial' amount would be fell on the courts, being settled in the UK courts in the 1930s.

The defining case of what a 'substantial' amount is is Hawkes & Son (London) Ltd v Paramount Film Service Ltd, which concerned the song "Colonel Bogey". The plaintiffs in the case were the owners of the copyright to the song in question, a march written in 1914, often used in military settings. The song was subsequently used by Paramount Film Service in a newsreel of the opening of the new Naval College. The reproduced part of the march lasted for an approximate 20 seconds in the newsreel, with the entire march being roughly 4 minutes long. The incidental inclusion of the song was also considered; however our main focus would be on whether that 20 second snippet from the song could amount to a 'substantial' part of the song, therefore infringing the plaintiff's copyright.

The UK Court of Appeal tackled the matter after it was initially dismissed by Justice Eve at first instance. In the Court of Appeal's view the matter boiled down to assessing the copied material not merely based on quantity, but other factors as well, or as presented by Lord Hanworth MR: "...we must look into the question of degree and what was the nature of the reproduction". Agreeing with Lord Hanworth, Lord Justice Slesser further developed the Court's view on the matter:

"I agree with my Lord that this reproduction is clearly a substantial part of 'Colonel Bogey', looked at from any point of view, whether it be quantity, quality, or occasion. Any one hearing it would know that it was the march... [and] it is clearly, in my view, a substantial, a vital, and an essential part which is there reproduced."

Not that Colonel

Now what can be taken from Lord Slesser's view is that a 'substantial' part of a work can be any amount, not merely a large part of it through a purely quantitative analysis. His Lordship talks about recognition, and although one can argue that this view is a particularly weak one, one can say this would be much akin to what was stated in Harper & Row Publishers v Nation Enterprises; the "heart" of the work. The part which was copied has to be essential and vital to the work as whole, and recognition plays a part in that. For example a very  recognizable introduction to a song or a particularly memorable riff in the middle can be a substantial part if deemed sufficiently vital to the work as a whole.

As can clearly be seen what is 'substantial' is purely subjective and assessed by the court according to each instance, not providing a clear-cut rule which applies to all works. What is deemed 'substantial' in each instance will vary depending on the type of work in question, how it has been modified (if at all), and whether it is sufficiently important to the work as a whole. Under modern laws there are exceptions aplenty for a variety of uses, which did not exist under the UK Copyright Act 1911 at the time of the case, but the case still remains an important part of the common law system in copyright infringement.