At a time when evidence in digital format has become a normal aspect of the large majority of legal proceedings across the globe—civil and criminal—this text by Hock Lai Ho is a timely addition to the literature on evidence and the legal process. The premise of the text is offered on page 1, that there is ‘more of value in our common law heritage of evidential issues than the critics allow’, and many of the rules express principles that are integral to the epistemic and ethical justification for the decisions reached in legal proceedings.

The underlying rationale of the book is that the finder of fact acts as a moral agent. Evidentiary findings by a court must, naturally, be justifiable; but Ho suggests that such findings must also meet the demands of epistemic rationalityFootnote ² and ethics, and in so doing, reflect the interests of those participating in the justice system in seeking the truth and in doing justice. Ho's discussion centres on the adversarial trial, taking into account two standpoints: that of the finder of fact (internal), and that of the outsider (external). He addresses three features of the rules of evidence in detail: the standard of proof, the rule on hearsay evidence and the rule on similar fact evidence. After carefully considering and rejecting suggestions that such rules pose technical and unwarranted obstructions on the search for truth, Ho ultimately concludes that such rules further the court system's interest in obtaining truth and in doing justice.

The first two chapters are by way of introduction. Chapter 1 analyses certain aspects of fact finding that are considered to be fundamental, such as the role of facts and their classification and the major components taken into account in the deliberation of a trial, including the legal techniques employed in controlling the process. Chapter 2 then considers the values and purposes of the trial, and analyses the debate on the claim that the trial process seeks the truth, exploring the connection between truth and justice. This leads into chapter 3, which deals at length with the epistemic aspects of fact-finding, in which a belief account of fact-finding is discussed and defended, the acquisition of relevant beliefs is outlined, and the methods and form of deliberation are considered.

Three separate chapters then deal with the topics selected for detailed treatment, with chapter 4 discussing the standard of proof. The author proposes a variant on the interpretation of the standard of proof that is compatible with maintaining the distinction between the civil and criminal standards, focusing on the ethics and epistemology of the deliberation of the trial. Ho suggests the standard of proof centres on the exercise of the right degree of caution. Deliberating on the evidence presented at trial should reflect three values: truth, respect and concern. In doing justice, the fact finder should exercise a ‘standard of caution’ towards the person who will be affected by the decision, taking into account the need for integrity (they are justified in believing the facts), and humanity (reflecting a caution that shows respect and concern for the interests of the individual). It follows, Ho then suggests, that there are two kinds of ‘attitude’ when interpreting the standard of proof: the ‘attitude of impartiality’ in civil cases and a ‘protective attitude’ in criminal cases. In civil cases, this simply means that the fact finder should treat the parties equally – though the value of this formulation is perhaps unclear, as it is difficult to understand how a fact finder can do anything other than treat the parties equally. Of more interest is the ‘protective attitude’ in criminal cases, where Ho suggests the fact finder should exercise greater caution in finding against the accused than for him. In trials where there is a single fact finder, as opposed to a jury, such a frame of mind might be a useful benchmark to adopt.

In chapter 5, in his analysis of hearsay evidence, Ho points out that hearsay evidence is excluded in the interests of ensuring the verdict is correct. Ho indicates that the exclusion is founded, in general, on two assumptions: that the members of the jury are not competent at evaluating hearsay evidence, and the statement of a person who has not been cross-examined is not reliable. Generally, the hearsay rule is usually considered from an external point of view: that is, the effect the rule has on the capacity to reach a correct verdict. In turn, this analysis tends to focus on causal links between the empirical assumptions upon which the rule rests, and the effectiveness of the trial as a method of inquiry. Ho argues that there are deficiencies in this approach. In considering the competence of the jury, he concludes that a single judge, because of the office they hold and their training, is better at handling hearsay evidence than members of a jury. However, and more importantly, he also considers this issue from the point of reliability. In this respect, he considers that hearsay evidence is excluded because its reliability is not known (in that information might be lacking or there are other aspects of the evidence that have not been explored), as opposed to it being unreliable (or being assumed to be unreliable). Ho acknowledges that the trial is also perceived as a process of acquiring such moral authority that the person whose case is before the court will accept the decision. In this respect, a decision based on hearsay may undermine any such moral claim where it is unjust to draw such an inference in the absence of knowledge that is believed (called ‘epistemic justification’ by Ho), which is of central concern.

Chapter 6 deals with the rules on similar fact evidence, which Ho indicates have a moral basis beyond logic. The probative value of the evidence is not the ultimate criterion, but rather previous conduct is excluded for ethical reasons that relate to considerations of fairness and justice. Ho suggests that the traditional views for exclusion stand on empirical premises that are contestable, conceptually vague or not easy to verify. In addition, he considers they are in need of deeper explanations, and considers these criticisms from the point of view of the finder of fact, and that of the outsider. For instance, one question considered is how the rule affects the probability of getting the facts right in the end. Ho suggests that there is a perceived tension between empirical claims made about the consequences of admitting evidence of previous misconduct (the evidence might not relate to misconduct, so much as a strikingly similar set of facts) and how the rule affects reliability. Where there is evidence that the accused has committed similar crimes, many people may consider this to be relevant, and if the judicial process is interested in the truth, then the evidence should be admitted, although the evidence might not be conclusive. However, the evidence is potentially prejudicial, and therefore capable of leading the finder of fact away from the correct factual conclusion, which may obstruct the discovery of the truth. In concluding, Ho indicates that the rule regulates the trial in two ways. First, it prevents the finder of fact from reasoning that the accused is likely to commit the alleged crime because he is likely to have committed it because of previous misconduct. The rule deals with this lack of integrity in the reasoning process. Second, the accused's past cannot be directly relevant, otherwise if his past were to be adduced, it would act to dismiss his moral autonomy. It is for these reasons, Ho concludes, that the similar facts rule acts in the interests of doing justice to the accused in the pursuit of truth.

This book is of particular relevance in the context of the unique characteristics of digital evidence. This is because of a range of factors, including, but not limited to, the complexity of digital evidence, the potential volumes of evidence, the difficulty of finding evidence and persuading the judge to order additional searches, the ease with which digital evidence can be destroyed (that is, by physically destroying the hard disk, as opposed to deleting, overwriting or reformatting files or hard drives), the costs of such exercises, as well as the lawyer's lack of technical knowledge when dealing with this form of evidence.

Of significance is Ho's emphasis on two central requirements, that legal decisions must be logical and the facts must be correct. Arguably, some lawyers and judges may be failing to abide by these requirements, especially when making decisions about the digital evidence a party needs to submit to prove its case. This is illustrated by the criminal case of the State of Connecticut v Julie Amero,Footnote ³ in which a substitute teacher was prosecuted after a computer she was using in a classroom began uncontrollably to display pornographic images, which some students subsequently saw. A number of important mistakes were made in this case: it seems the ‘specialist’ police officer conducted his examination of the hard drive on the original hard drive, rather than a copy of the hard drive; the tool used was not appropriate; it is debatable whether the police officer was sufficiently qualified; the prosecutor was surprised mid-trial that malicious software was found on the computer; the defence hired an expert witness, and failed to give a copy of the report to the prosecution in advance; the qualifications of the defence expert would be debatable in many jurisdictions; technical assertions made by the police officer about clicks of the mouse alleged to be made by the substitute teacher, and therefore to prove she deliberately obtained access to web sites of a dubious nature, were later demonstrated to be incorrect, and the images that were shown to the members of the jury were viewed many sizes greater than the image that originally appeared on the computer screen. Arguably, the learned judge could have ameliorated some of the failures of both the prosecution and defence in this case, by insisting that the prosecution consider the expert report form the defence overnight, and gave proper consideration to the size of the images displayed before the members of the jury.

Ho's arguments are also relevant to the issue of the costs of digital evidence. Of increasing concern in modern cases is the cost of finding and submitting digital evidence – and in addition, the resistance, especially of banks, to submit proper evidence to support their assertions, in particular with respect to withdrawals of cash from ATMs where the cardholder neither used nor authorized the use of their card and PIN to withdraw cash from an ATM. Generally, the banks resist the requirement to prove their case by making wide assertions in witness statements about the ‘security’ of their banking systems, and arguing that the costs of bringing such evidence to court is disproportionate to the amount at issue. Unfortunately, the complexities that accompany evidence in digital format add to the cost of a case, even where the amount in dispute might be comparatively insignificant (at least for one of the parties). In England and Wales, Civil Procedure Rules expressly include provisions to deal with cases with an eye to the cost, and to keep the costs of legal action within reasonable bounds.Footnote ⁴ However, this may cause those participating in the legal system of the twenty first century to lose sight of certain fundamental concerns. As Ho points out at page 49, the ‘court must not only find truth in order to reach a just outcome, it must also do justice in the course of ascertaining the truth’, and suggests that the parties may be rightly aggrieved if concerns of procedure and costs override the search for truth. In this respect, Ho has written an erudite and timely text that lawyers and judges ought to consider reading to enhance the proper working of the judicial system, especially in the age of digital evidence.