Select Committee on Science and Technology Fifth Report


Requiring the original image to be produced to the court

  3.10     One possibility for overcoming the problems of digital images would be to require the production of the original as evidence before the courts (Liberty p 11). However, as discussed in Chapter 2, a fully electronic process provides no physical original. Provided the necessary verification and authentication measures are in place, we think this suggestion is misplaced. Nonetheless the very suggestion gives rise to the apparent need to keep original pieces of paper when documents are imaged for subsequent electronic handling.

  3.11     One of the key implications of the growing availability of digitally captured and stored images (whether of documents or pictures) is that the erstwhile reliance on paper and photographic originals (or authenticated copies of these originals) is no longer always going to be feasible for use in court. For example the National Automated Fingerprint Identification System has no original paper source to retrieve as 'best evidence' in a court of law (p 126). Provided that verification and authentication measures of digital material are in place, paper originals will rarely be necessary. Yet the evidence we have received suggests that there may still be some reluctance to come to terms with this development. We recommend that the Government encourage the appropriate legal bodies to draw greater attention to this change and to widen public awareness that paper originals are rarely necessary.

  3.12     A modification of the suggestion that only originals should be admissible as evidence is that where an image has been enhanced or otherwise altered intentionally, any use of the modified copy as evidence should be accompanied by the unaltered image (Justice Q 26, Liberty p 11). The founding testimony which explains the source of the image would be expected to disclose whether modification had taken place (eg in the forensic laboratory) and other parties would be entitled to copies of the unaltered image. But what assurances are there that the image was not altered before being used as evidence? There is a danger that legal advisers do not understand the possible effects of enhancement or they do not recognise that other evidence for the provenance of the image may be required, or both. These dangers would be compounded when there are insufficient resources to secure expert legal and technical advice.

  3.13     In this context proposals were made to us for changes to the law. For example, that the rules for civil and criminal procedures should be amended so as to require any person putting forward a digital image as evidence to disclose to the other side an authenticated copy of the image prior to processing and details of that process.

  3.14     In this, as in the other areas, we were not convinced that rewriting the law in an attempt to keep pace with technological change was a sensible approach. The certainty we have is that technology will continue to change. No less certain is that the rate of change will increase. Thus, we agree with the Data Protection Registrar (Q 222) that attempting to extend legislation by introducing specific technological caveats to take account of the latest technology is unlikely ever to be a successful approach.

Excluding the use of digital images as evidence unless specific requirements are met

  3.15     Some witnesses (eg Liberty p 4, Mr Sommer, p 45) suggested that digital images should only be admitted as evidence if the technology used to capture those images incorporated some form of authentication technology such as watermarking or a digital signature. Indeed, Mr Sommer went as far as saying that "without authentication digital images are worthless".

  3.16     We have outlined earlier the existing requirements for admissibility of evidence (see Chapter 2). The arguments against specifying new criteria which must be met before evidence can be admitted are:-

it would be very difficult to specify the nature of the authentication technology in such a way that it would not quickly become outdated as the technology advances.

it would take an appreciable time for manufacturers of digital image technology to incorporate such measures, and even longer for such technology to become widely used;

when technology advances, the courts will be faced with the position that images over which there was no dispute as to their reliability cannot be received as evidence because they were not captured by technology which met the required specification; and

the clear trend in the development of the law is to remove prior requirements for all forms of documentary evidence, leaving it to the courts to determine whether the evidence is in fact reliable.

  3.17     For these reasons we are not convinced that some sort of criteria must be met before evidence can be admitted. Rather we agreed with the witnesses who said that there should not be different rules about admissibility based on the technology used to capture the evidence (eg IBM Q 306). There might be occasions where the most mundane home video could produce very useful evidence for the court which would be unlikely to be disputed. Neither would we wish to exclude the vast majority of business documents and other images in use today which may not meet some technical standard or other (cf Mr Smith Q 95, IBM p 99). Similarly, one can hardly expect those engaged in criminal activities to conform (Mr Sommer Q 118)!

  3.18     We recommend that evidence should not necessarily be inadmissible because it does not conform with some specific technological requirement.

  3.19     But, although we recommend that there should be no technological requirements which all digital images must meet before they can be admitted in evidence, this does not mean we are against authentication technologies. It is a matter for the courts to determine the evidential weight and reliability of an image, including the effects of any modification. We support the application of any technology which can help with the verification of an image and provide assistance to the courts in assessing the worth of the evidence before it.

  3.20     We recommend that the Government encourage the use of authentication techniques. Members of the legal profession should be made aware of the benefits of these techniques, their value in adding weight to evidence and the possible significance of their omission.

  3.21     Technical procedures are only part of the authentication process or audit trail. In addition the provenance of evidence can be enhanced by procedural measures. Good practice for handling digital documents has been set down by the British Standards Institution[22] but conformance with this standard is perhaps not as widespread as it could be. Certainly it is good business practice to conform to such standards in preparing documents that might be used in court. We recommend that the Government produce guidance on the benefits of conformance with procedural measures necessary to establish the reliability of evidence, with particular reference to existing standards. When this guidance is available, we recommend that the trade associations of those organisations likely to be concerned with it produce training material on its use.

Identification in the Criminal Court

  3.22     A real danger posed by digital image technology is that of misidentification, particularly in criminal prosecutions. The law is already alive to this danger and contains safeguards to ensure that undue weight is not given to identification evidence. In the 1960s a series of miscarriages of justice were caused by mistaken identification of defendants, and subsequently in the case of R v. Turnbull[23] the Court of Appeal (a full Court) laid down guidelines to be observed by judges when 'identity' is an issue. This has become known as the Turnbull Warning.

    "First, whenever the case against an accused depends wholly or substantially on the correctness of one or more identifications of the accused which the defence alleges to be mistaken, the judge should warn the jury of the special need for caution before convicting the accused in reliance on the correctness of the identification or identifications. In addition, he should instruct them as to the reason for the need for such a warning and should make some reference to the possibility that a mistaken witness can be a convincing one and that a number of such witnesses can all be mistaken ...

    Secondly, the judge should direct the jury to examine closely the circumstances in which the identification by each witness came to be made. How long did the witness have the accused under observation? At what distance? In what light? Was the observation impeded in any way, as for example, by passing traffic or a press of people? Had the witness ever seen the accused before? How often? If only occasionally, had he any special reason for remembering the accused? How long elapsed between the original observation and the subsequent identification to the police? Was there any material discrepancy between the description of the accused given to the police by the witness when first seen by them and his actual appearance? If in any case, whether it is being dealt with summarily or on indictment, the prosecution have reason to believe that there is such a material discrepancy they should supply the accused or his legal advisers with particulars of the description the police were first given ... Finally [the judge] should remind the jury of any specific weaknesses which had appeared in the identification evidence ...

    When, in the judgement of the trial judge, the quality of the identifying evidence is poor ... [he] should then withdraw the case from the jury and direct an acquittal unless there is other evidence which goes to support the correctness of the identification ..."

  3.23     More recently, the Court of Appeal has recognised that similar dangers are posed by video evidence of identity:

    "some at least of the considerations underlying the safeguards built into the regulatory procedures laid down for identity parades and the showing of photographs come into play too with regard to the showing of video tapes. Particularly in cases where the quality of the video is poor or the opportunity it provides for recognition is limited ... it would be desirable to regulate its showing so as to maximise the prospects of any recognition evidence being truly spontaneous and independent and minimise the risk of anything being said or done which might infect that independence and spontaneity and instead prompt the recognition of some particular person ... It is not for this court to suggest what the appropriate procedures should be; clearly regard will need to be had to the practicalities. We would, however, urge that some immediate thought be given to this matter at a high level"[24].

  3.24     In 1995, R v. Clare and Peach[25] demonstrated the ability of the law to adapt to video technology. The defendants were charged with offences of violence at a football match, the incident having been captured on an unclear, black-and-white video recording. A police officer compared this recording, frame by frame, with a high-quality, colour recording made of the crowd entering the stadium, and was thereby able to identify the defendants as having taken part in the violence. The Court of Appeal held that their conviction on this evidence was safe because an appropriate version of the Turnbull Warning was given to the jury. Lord Taylor said:

    "... as technology develops, evidential practice will need to be evolved to accommodate it. Whilst the Courts must be vigilant to ensure that no unfairness results, they should not block steps which enable the jury to gain full assistance from the technology"[26].

  3.25     To date the courts have not developed a definitive statement of the safeguards which will be necessary where video evidence has been collected by a source other than a public body, or where image enhancement has been attempted as part of the identification process.

  3.26     A further consideration arises in those cases which may be equally dependent on identification but where there is an image that unambiguously shows the defendant. It is not a matter of caution whether there can be a mistake in identifying the person whose image is submitted as evidence, of that there might be no doubt: it is a matter of caution over the probity of that evidence.

  3.27     We recommend that consideration be given to the Turnbull Warning being appropriately adapted so that the uncertainties inherent in images as evidence are made clear to the jury, particularly the implications of any measures to substantiate authenticity and breaks in the audit trail, and any processing which the image has undergone. This is a matter which the Judicial Studies Board may care to take up.

The current need for greater certainty

  3.28     It can be argued that existing law is likely always to be adequate and, where there is any uncertainty, this can be resolved by the courts in the normal process of building up case law. But allowing the precedents of case law to establish the legal requirements, is a lengthy and for the trailblazing litigant an expensive process. We noted a marked reluctance of both civil (Abbey National, QQ 324, 344) and criminal authorities (City of London Police) to be the first to become involved in litigation about digital images. If no cases are heard, no case law is developed-and uncertainty grows. With large investments hinging on the outcome, case law is not an ideal way of establishing the necessary legal confidence. A number of witnesses, including the Abbey National (QQ 375-379), the BSI (QQ 196-200) and Mr Sommer (Q 117) called for a code of practice or guidance for handling computer derived evidence: something "to give the managers confidence to take that leap and start to move away from this paper culture that we are now in" (Abbey National Q 376). The uncertainty must be resolved. The matter could be tested by a claim for a declaration in the High Court by means of a friendly action brought by a major institution; alternatively it could be the subject matter of consideration by the Commercial Court Users Committee; or the Government might consider issuing guidance, which of course would not be binding on the courts. We recommend that consideration be given to these matters and the Government ensures there is a satisfactory resolution of the uncertainty.

Maintaining confidence in the accuracy of the image

  3.29     A danger frequently pointed out to the Committee was that of portraying image enhancement as an entirely objective science, particularly where an operator was manipulating the image to look for a suspect. It can become a largely subjective exercise. It might be possible, with certain software (eg the Home Office 'IMPROVE' software), to reproduce any changes, but this makes them no less subjective. Put at its simplest: if an operator is looking for a white car there is a temptation to increase the brightness of the image of a grey one; conversely when looking for a black car, the brightness is reduced (Liberty Q 5). This might occur without any malice. It is a simple desire to find what is being searched for: "the well intentioned mistake" that could lead to a miscarriage of justice (Mr Sommer Q 123). However we were told by the Home Office (p 127) that although the use of IMPROVE had been widespread since 1990, it had not been challenged as evidence.

  3.30     Where the record has been altered, or the technology allows the possibility of alteration, the user will need to be able to prove that the image is authentic. Doubts will arise where there is a possibility that through human or machine error the record has become corrupted or confused with some other record[27]. Doubts will also be raised if fraud is suspected but, and this is an important point at the centre of many of our recommendations on awareness, the apparent credibility of an altered digital image may mean that fraud is not considered in the first place (eg Mr Sommer Q 140).

  3.31     Furthermore, there is a danger that an altered image could be given an authenticating mark if the authentication were not done at the time of image capture. The value of such technologies would then be compromised. We also recognise that any authentication technology, however sophisticated, has the potential for being circumvented. Authenticating technologies will thus need to keep ahead of the abilities of those who set out to undo them. But these apparent shortcomings are possibly less real in practice than in theory. Our witness from IBM said of circumvention technologies: "in all of these processes the only thing that you can do is make it very difficult, and if you can make it difficult enough, such as that the process takes too long, then you are at least achieving part of your aim" (Q 292). We concluded that watermarks can be used to great advantage: they can provide a high level of security in conjunction with an audit trail and the cost of introducing a watermark to an image is likely to be low relative to the costs of trying to circumvent it. Of course the veracity of the witness presenting evidence should be considered alongside the evidence itself (QQ 99, 118).

  3.32     What is important is to encourage the adoption of authentication technologies by creating a wide understanding of the benefits from the level of security they can provide. The technologies are advancing rapidly and there will also be the need to provide regular updates to both the users and suppliers on improvements and changes. The Government already gives 'type approval' for certain enforcement technologies using images as evidence and we see the measures set out above as an extension of this.

  3.33     We recommend that the Government encourages the adoption of technological measures for the authentication of images as evidence by giving type approval to them. The Forensic Science Service should provide ongoing advice for manufacturers and users of imaging equipment on authentication technologies.

  3.34     We noted in paragraph 3.6 that hitherto audit trails have not been demanded in cases where video images were used by the prosecution and in paragraph 3.11 we have made a recommendation on the need for greater public awareness of the particular circumstances relating to the need for paper originals. Overall we see a need for awareness by all those concerned with the potential difficulties with digital evidence. We recommend that the Judicial Studies Board consider establishing a programme of education on the implications of digital technology for the judicial system.

  3.35     But if there is increased awareness, the defence may have insufficient financial resources to undertake technical investigations and to secure expert witnesses capable of challenging the reliability of an image. This is likely to be a particular problem where the defence is funded by legal aid. What is needed is some mechanism to make compliance with good practice, conformance with codes of management and the application of technological measures, accepted normal practice.

  3.36     Voluntary standards and codes exist for the procedural measures necessary for document handling (eg the BSI code). We have recommended that similar codes and standards be put in place to encourage the use of technological measures to authenticate images. The advantage of such voluntary standards is that they can be changed to keep pace with changes in technology (or made substantially independent of it), they represent the consensus of those in the field and enable a far more flexible approach than is possible with regulation. But to achieve the full benefits from such codes there must be an incentive to comply with them. This is achieved in other areas by making compliance with an approved code a recognised way of showing that legal requirements have been met or that good practice has been achieved. We recommend that the Government devise incentives or put in place measures such as the endorsement of relevant codes, to increase the adoption of good practice.

22   BSI DISC PD 0008, see footnote to paragraph 3.2. Back

23   R v. Turnbull (1977) QB 224 Back

24   R v. Caldwell & Dixon (1993) 99 Cr App. Rep. 73, 78 per Brown Wilkinson LJ.  Back

25   R v. Clare and Peach (1995) 2 Cr App. Rep. 333.  Back

26   (1995) 2 Cr App. Rep. 333, 339.  Back

27   Such doubts can be overcome by producing evidence as to the technical efficiency of the system, the maintenance of logs sufficient to indicate problems, error-checking procedures, management and training of staff, etc. Adherence to technical standards will assist in authentication, although even standards which are designed to achieve authentication cannot be guaranteed to do so, as English law has no system of certification which would raise a presumption of authenticity. Back

previous page contents next page

House of Lords home page Parliament home page House of Commons home page search page enquiries

© Parliamentary copyright 1998