DNA evidence - Under the microscope

By EUGENE BINGHAM

Beyond the headline-grabbing exposure of DNA botchups rages a wider debate about core principles of our justice system.

Defence lawyers, prosecutors and forensic scientists are in the midst of a crucial argument about what material should be made available to defendants facing cases built on DNA evidence.

Such a debate is fundamental to one of the central tenets of our justice system - the right of an accused to a fair trial.

The issue has been highlighted in a Ministry of Justice report on DNA evidence and how forensic scientists present results in court.

The report was written by a team of senior officials appointed to investigate procedures at the Institute of Environmental Science and Research (ESR) after Peter Robert Howse was freed on a rape charge which subsequent DNA tests showed he almost certainly committed.

In carrying out their investigation, the officials could not avoid the festering issue of disclosure: the prosecution's legal duty to divulge information central to the Crown case or relevant to the defence.

One of their recommendations was to "invite" ESR to revise its disclosure requirements to make more information available to the defence. The institute has already indicated it is not eager to do this.

The ministry made its recommendation after reviewing what happens with DNA results that require interpretation on the part of the scientist. DNA testing does not always give clear-cut results, despite the widespread belief to the contrary.

In most cases, scientists can compare a crime-scene sample with a sample taken from a suspect and make a clear-cut decision on whether they match.

Sometimes, however, an interpretative judgment is required, for example if the test produces a mixed result in which the DNA of more than one person is found.

As one of its quality control checks, ESR has a system of peer review which the ministry found to be satisfactory.

The officials point out, however, that the notes, drafts and conclusions of such reviews, including records of disagreements, are not always kept on the case file or made available to the defence.

"It is of crucial importance to the defence to know whether results are marginal, or of any interpretative difficulties," says the ministry report.

"In particular, defence counsel need to be able to make informed judgments about whether or not independent scientific expertise should be sought."

The information must be available, to ensure the system works effectively. This will help lawyers identify early any issues about the DNA testing and, where necessary, to challenge any interpretations.

The ministry's conclusion has been hailed as a breakthrough by some defence lawyers who have complained about the problems with obtaining information.

The convener of the Law Society's criminal law committee, Judith Ablett-Kerr, QC, said it was vital for defence counsel to have access to material from forensic laboratories and the right to seek their own tests.

She speaks from experience. Her defence of Christchurch biologist Dr Vicky Calder in the "poisoned professor" case four years ago revolved around contesting the Crown's scientific evidence.

Though the case did not involve DNA evidence, it was fought over scientific tests by the defence and prosecution.

"I was fortunate in the Calder case that I managed to get pretty good disclosure from them but things have changed since then and some matters are not disclosed," said Mrs Ablett-Kerr.

Armed with a wealth of scientific data, she was able to demonstrate to the jury differences between the ESR results and those of independent analysts.

Dr Calder was found not guilty in her second trial on charges relating to the alleged poisoning of her former lover, Professor David Lloyd.

Justice Minister Phil Goff has backed moves to give defence lawyers equal rights of access to ESR information and to make sure the notes and drafts are held on the case file and are available to the defence.

"What we're aiming to do is not only succeed in prosecuting but to be more confident that when we get a prosecution we get the right one.

"Wherever you have a technique that involves human procedures and human interpretation, then you cannot say you have an infallible technique and it's important you have safeguards."

At the ESR, however, the issue is not straightforward.

Dr Keith Bedford, of the institute's forensics unit, said the disclosure and defence access issues were "quite thorny."

Asked if the institute accepted the principle of the defence having rights of access, he said: "We're not disputing that - it's the mechanism we are concerned about clarifying and formalising.

"The requirement to disclose is something that we recognise as a moral obligation but there are no guidelines or protocols in place around what is expected to be disclosed and how that is to be managed."

At the heart of ESR's concerns are two issues: money and privacy.

"I'm not making resources the issue," said Dr Bedford, "but the cost of preparing copies of files which can be literally thousands of pages of technical output and data is not insignificant.

"There are also issues around privacy because we may hold in our lab files information on suspects who have been excluded in the course of the investigation and information relating to what we describe as reference samples - the boyfriend of the complainant, a family member, that sort of thing.

"It's not just a matter of duplicating a file and sending it off when it's requested."

Dr Bedford said ESR and Crown Law were working on guidelines for prosecution lawyers. From that, protocols for defence counsel could also be developed.

Beyond ESR's concerns about the practicalities of providing more information to defendants is a broader philosophical contention.

"Disclosure is an obligation on the prosecution," said Dr Bedford. "ESR is not the prosecution - ESR provides an impartial scientific service to help the justice system reach scientifically appropriate conclusions."

(A recent High Court decision has thrown doubt on the argument that ESR is independent of the Crown in terms of disclosure.)

Auckland University Law School evidence expert Scott Optican said the whole debate demonstrated the wider problem with disclosure rules in New Zealand.

"Despite urgings over many years, NZ doesn't have one comprehensive, all-inclusive statute telling everybody what they need to disclose, when and why."

Until the rules were set down, the arguments would rage on, he said.

"We really need a statute to give judges guidance on how to approach these questions, to make firm lists of categories of disclosure and the timing of disclosure."