Our society is facing a growing dependency on services supported by multiple interconnected computing and cyberphysical artifacts, constituting complex systems-of-systems. Such dependence means that a web of technology suppliers and IT departments have the responsibility to guarantee the operational quality of such systems. In this scenario where dependable services are maintained and evolved by networks of organizations, the question is how to ensure a liability framework able to reduce or help to solve potential legal conflicts. This work on liability in Collaborative Maintenance of Critical System of Systems grounds on previous research on the open Informatics system of systems (ISoS) framework. It extends the ECoNet collaborative network infrastructure with facets to support liability and maintenance. We propose and discuss a strategy for the management of evidence towards a conflictless collaborative context for the maintenance of critical systems-of-systems.