We are living in what is usually described as an \'information society\' and as the business community makes ever greater use of computers the courts are going to find that increasingly the disputes before them turn on evidence which has at some stage passed through or been processed by a computer. In order to keep in step with this practice it is vital that the courts are able to take account of such evidence. As the Criminal Law Revision Committee recognised, \'the increasing use of computers by the Post Office, local authorities, banks and business firms to store information will make it more difficult to prove certain matters such as cheque card frauds, unless it is possible for this to be done from computers\' (CLRC 1972, para 259).


The law of evidence is concerned with the means of proving the facts which are in issue and this necessarily involves the adduction of evidence which is then presented to the court. The law admits evidence only if it complies with the rules governing admissibility. Computer output is only admissible in evidence where special conditions are satisfied. These conditions are set out in detail in section 69 of the Police and Criminal Evidence Act (PACE) 1984 (see further Nyssens 1993, Reed 1993 and Tapper 1993).

In general the principles of admissibility are that the evidence must be relevant to the proof of a fact in issue, to the credibility of a witness or to the reliability of other evidence, and the evidence must not be inadmissible by virtue of some particular rule of law (Keane 1994, pp 15-20; Tapper 1990, pp 51-61).

Real evidence usually takes the form of some material object (including computer output) produced for inspection in order that the court may draw an inference from its own observation as to the existence, condition or value of the object in question. Although real evidence may be extremely valuable as a means of proof, little if any weight attaches to it unless accompanied by testimony which identifies the object in question and explains its connection with, or significance in relation to, the facts in issue or relevant to the issue.

This is illustrated in the case of R v Wood (1982) 76 Cr App R 23 where the appellant was convicted of handling stolen metals. In order to prove that metal found in his possession and metal retained from the stolen consignment had the same chemical composition cross-checking was undertaken and the figures produced were subjected to a laborious mathematical process in order that the percentage of the various metals in the samples could be stated as figures. This was done by a computer operated by chemists. At the trial, detailed evidence was given as to how the computer had been programmed and used. The computer printout was not treated as hearsay but rather as real evidence, the actual proof and relevance of which depended upon the evidence of the chemists, computer programmer and other experts involved.

The difficulty in the application of this rule lies in its interaction with the hearsay rule. Evidence is hearsay where a statement in court repeats a statement made out of court in order to prove the truth of the content of the out of court statement (Sparks v R [1964] AC 964). Similarly evidence contained in a document is hearsay if the document is produced to prove that statements made in court are true (Myers v DPP [1965] AC 1001). The evidence is excluded because the crucial aspect of the evidence, the truth of the out of court statement (oral or documentary), cannot be tested by cross-examination. (1) The problem, however, occurs because some statements, although in form assertive and inadmissible if they were to originate in the minds of human beings, in fact originate in some purely mechanical function of a machine and can be used circumstantially to prove what they appear to assert.

The basis for this view was laid down in a case having little to do with computers. In the Statute of Liberty [1968] 2 All ER 195 a collision occurred between two vessels on the Thames estuary. The estuary was monitored by radar and a film of the radar traces was admitted into