This research presents an experimental model and prototype to exploit digital evidence in Internet of Things (IoT). The novelty of this research is to consider new data privacy mechanisms that should be implemented in IoT, in compliance with the GDPR regulation, and their impact on digital forensic processes. The testbed is an innovative project for car navigation [1, 2], GDPR compatible, which offers users the possibility to submit their GPS position into a blockchain for obtaining road traffic information and alternative paths. The vehicles are communicating among themselves through IoTs and circumvent the use of third-party services. We propose a solution for forensic investigations of such a service by building a solid case thanks to the non-repudiable, immutable, identifiable as current and authentic properties of data logged into the blockchain. This solution applies to criminal and insurance cases, where law enforcement and individuals need to prove their claims.