In G Urbas and K-K R Choo, ‘Resource Materials on Technology Enabled Crime’, Technical and Background Paper no. 28, Australian Institute of Criminology, 2008, techniques of cybercrime investigation are described (p 49):

Law enforcement officers, usually assisted by trained computer forensic analysts with specialist skills in computer investigations, play a critical role in relation to electronic evidence. The strict evidentiary requirements for criminal prosecutions mean that there must be a demonstrable chain of custody in relation to any evidence collected, so that no reasonable doubt can be raised in relation to the authenticity and integrity of the data presented to court. To establish a chain of custody, organisations should ideally:

create an evidence copy of an electronic record. Such copies can be created by various means including reproducing the electronic record as a printed document or copying the electronic record to storage media (e.g. backup tape).

maintain a custody log of the evidence copy, recording details such as who accessed the evidence, when the evidence was accessed and returned (if evidence was removed) and why the evidence was accessed.

In particular, verification is needed that the contents of a computer have not been created, deleted or modified during search, seizure and subsequent analysis. In this regard, it is critical that the analysis be undertaken by appropriately trained and skilled computer forensic analysts …

If such evidentiary standards are not followed, what adverse consequences might there be? Are there other ways of ensuring integrity of investigations?