Computer program infringing materials are difficult to identify. There are common techniques to disguise the origin of copied codes. In order to decide on a legal basis whether a substantial part of copyright work has been taken, it is necessary to consider both the quality and quantity of the part taken. Various researches have carried out in relation to authorship identification and plagiarism identification. In a criminal case in Hong Kong, we used a common software to compare files contents and folders between a copyright work and the infringing copy instead of complex and technical metrics. We conclude that the source codes of the defendant started from the source codes of his previous employer using simple and easy to understand measurements. Though the magistrate was satisfied beyond reasonable doubt of the defendant’s guilt, the evidence in the case did not enable a scientific calculation in respect of the likelihood that a computer program may look like a derivative of another program by chance.postprintThe 33rd ACM SIGPLAN Conference on Programming Language Design and Implementation (PLDI 2012), Beijing, China, 11-16 June 2012. In Proceedings of the PLDI, 2012, p. 1-1
