## Facts

- The defendant, a software developer, created and released “Winny,” a peer-to-peer (P2P) file-sharing program that allowed users to exchange many kinds of digital data through a decentralized network.
- Winny could be used for lawful purposes (such as sharing non-copyrighted data) and could also be used to share copyrighted works without authorization.
- Winny’s design made copying and sharing files easy, and it included functions that could make user activity harder to trace.
- The developer made Winny available to the general public over the internet, distributing it without charge as part of an ongoing development process.
- After Winny’s release, some users used the program to upload and share copyrighted works (including films and video games) without permission from rightsholders.
- In proceedings arising from users’ unauthorized sharing of copyrighted works, the developer was pursued on the theory that by creating and distributing Winny, he knowingly aided the users’ copyright infringement as an accessory (幇助).
- The trial court found the developer liable as an accessory to copyright infringement and imposed a fine (reported as 1.5 million yen).
- The intermediate appellate court ruled in the developer’s favor (reversing the accessory-liability finding), and the matter proceeded to the Supreme Court for final review.

## Issues

1. Whether a person who develops and publicly distributes a “value-neutral” tool like P2P file-sharing software can be criminally liable as an accessory to users’ copyright infringement.
2. What level of knowledge and acceptance (mens rea) is required for accessory liability when the alleged assistance is the provision of software usable for both lawful and unlawful purposes.
3. Whether awareness that some users are infringing through the software is enough, without proof that the provider recognized and accepted either specific impending infringements or a highly probable, non-exceptional pattern of infringing use.

## Decision

- The Supreme Court held that the developer was not guilty as an accessory to copyright infringement.
- The Court concluded that merely developing and distributing dual-use software, even with awareness that infringement can occur, does not by itself satisfy the intent required for criminal aiding and abetting.
- The Court entered an acquittal, rejecting accessory liability on the record presented.

## Legal Principles

- Accessory liability for copyright infringement based on providing software requires more than (a) the software’s capacity for infringement and (b) the provider’s general awareness that some users may infringe.
- Where the alleged assistance is distribution of a generally usable tool, aiding and abetting is established only if the provider recognized and accepted, at the time of distribution, one of the following:
  - a concrete, specific copyright infringement that was actually about to be carried out using the software; or
  - that, considering the software’s nature, its objective usage, and the method of provision, there was a high likelihood that users beyond an “exceptional” range would use it for infringement, and the provider accepted that likelihood.
- The Court treated Winny as “value-neutral” software: whether it is used for lawful or unlawful ends is determined by users, not by the tool itself.
- In assessing mens rea for accessory liability, courts must avoid extending criminal responsibility so broadly that ordinary software development and public distribution methods are chilled.

## Conclusion

Saiko Saibansho Daisan Sho Hotei (Dec. 19, 2011) held that criminal accessory liability cannot rest on distributing a dual-use P2P program alone; the prosecution must prove the provider’s recognition and acceptance of either specific impending infringements or a highly likely, non-exceptional pattern of infringing use at the time of provision, and that standard was not met for the Winny developer.


Saiko Saibansho Daisan Sho Hotei [Supreme Court Third Petit Bench], December 19, 2011, Heisei 21 (A) no. 1900 (2011)