There are three parts which must all be proven true to meet the "Authenticity" criteria. The evidence must be obtained from the computer in question, the evidence must be "complete and accurate" and it must "remain unchanged" since collection [1].
Proving that the evidence has not been tampered is relatively straightforward through the use of file hashes which will change whenever a file is modified even slightly [2]. Furthermore, any attempt to boot the machine will result in modification of timestamps of files within the disk thus proving that it has changed since collection [3].
Proving that it is accurate or reliable is more challenging due to "increasing variety and complexity" of computers [4]. With the repeal of Sect. 69 of PACE, computers are assumed to be reliable and the burden of proof has shifted onto the defendant to show that it was malfunctioning [5].
Finally, proving that evidence was acquired from the correct computer and its completeness relies on chain of custody documentation [6]. Law enforcement must record all details when handling evidence which is to be submitted as documentary evidence. The law assumes that law enforcement officers are honest in all their actions.
However, there have been cases where officers have planted evidence [7]. In this case, the deception was uncovered because the officer forgot to switch off her body camera [8]. Perhaps, switching to a live stream which is saved remotely would reduce the opportunity for such actions to occur. In the digital realm, blockchains providing timestamped immutable storage has been mooted as a possible alternative to relying on a human updated document [9]. However, because so much activity on a computer generates logs and timestamps, it is also much harder to plant digital evidence. When the only incriminating file had a creation timestamp that coincides with the raid and evidence seizure, it will be hard to convince the court that the suspect decided to start offending just as law enforcement arrived. Hence, it might be argued that chain of custody documentation is sufficiently robust due to the difficulty of planting digital evidence.
[1] Eoghan Casey, Digital Evidence and Computer Crime Forensic Science, Computers and the Internet (Third edition., Academic Press 2011), pp. 60
[2] ibid
[3] ibid
[4] ibid, pp. 62
[5] ibid, pp. 63
[6] ibid, pp. 60
[7] Max Herrle, 'Video shows tallahassee police officer planting evidence during DUI arrest' https://ourtallahassee.com/video-shows-tallahassee-police-officer-planting-evidence-during-dui-arrest/ accessed 8 February 2025
[8] ibid
[9] Bonomi, Silvia, Marco Casini, and Claudio Ciccotelli. "B-CoC: A Blockchain-Based Chain of Custody for Evidences Management in Digital Forensics." arXiv.org (2018)