Cosmic rays: a neglected potential threat to evidential integrity in digital forensic investigations?

When evidence is recovered from a suspected crime scene and a criminal prosecution is mounted, the defence team may attempt to formulate an alternative non-criminal explanation for the existence of that evidence. Examples from the digital realm include the "Trojan Horse Defence" and the "Inadvertent Download Defence" against the charge of possession of child pornography, both of which have previously been analysed quantitatively. In this paper, another putative defence for the existence of forensically recovered data and/or meta-data from a seized digital device is described. The potential plausibility of this "Cosmic Ray Defence" under various memory protection conditions is estimated numerically as a function of its associated soft error rate (SER), thus enabling an evaluation to be made of its potential utility as part of a criminal defence strategy, as well as highlighting its possible significance for the conduct of digital forensic investigations. It is based on the invited keynote lecture at the 10th International Workshop on Digital Forensics (WSDF 2017), Reggio Calabria, Italy, 29 August - 1 September 2017.