In digital forensics, a write blocker is a critical tool used to prevent any modifications to the source drive during imaging. When a forensic image is created, it should be an exact bit-for-bit copy of the original evidence. If a write blocker is not used, system processes or other unintended changes can alter the contents of the drive, leading to a hash mismatch between the original and the image copy.
Chain of custody (Option A) ensures proper documentation of who accessed the evidence, but it does not directly affect the hash values.
Legal authorization (Option B) is necessary but unrelated to the technical integrity of the image.
Data integrity verification (Option C) is part of the process, but in this scenario, the failure to maintain integrity stems from the lack of a write blocker.
Thus, the correct answer is D, as using a write blocker would have prevented any unintended changes to the data.