CAUTION

Forensic Interpretation

In 1989, DNA evidence entered courtrooms with the promise of bringing science to criminal justice.

What few people realise is that in the very same year DNA also helped free an innocent man.

From the beginning, DNA proved to be more than a tool for conviction.

It became a tool for correction.

That simple fact should caution us against treating any forensic science as infallible.

If a scientific technique can both convict and exonerate, perhaps the real question is not whether science is reliable.

Perhaps the question is whether human beings always interpret it correctly.

Like every major scientific advance, DNA evidence arrived in a legal system that was still learning how to understand and evaluate it.

Judges suddenly found themselves being asked to rule on complex scientific issues.

Lawyers were required to understand concepts that had never previously appeared in criminal courts.

It took time for the legal profession to develop the knowledge and confidence necessary to properly test expert evidence.

The danger was not the science itself.

The danger was that juries, lawyers, judges and investigators could be so impressed by the authority of science that they stopped asking questions.

The most notable Australian example of this problem occurred before DNA profiling became common in courtrooms.

In 1982, Lindy Chamberlain was convicted of murdering her baby daughter, Azaria.

The prosecution's case relied heavily upon forensic evidence said to identify blood in the family vehicle.

Years later, one of Australia's leading forensic scientists, Barry Boettcher, demonstrated that critical forensic conclusions relied upon at trial were incorrect and that material believed to be blood was in fact sound-deadening compound.

The lesson was profound.

The issue was never whether science was valuable.

The issue was whether scientific conclusions had been properly tested before being accepted as fact.

When Science Loses the Ability To Correct Itself

Science is unique among human endeavours because it allows conclusions to be tested, challenged, and reviewed.

A scientific conclusion is never supposed to become immune from scrutiny.

But what happens when the evidence itself disappears?

In one case I am currently examining, the recorded cause of death was "unascertainable (consistent with asphyxiation)."

Those words are important.

They do not mean that asphyxiation was proven.

They mean that the cause of death could not be determined with certainty, although some findings were considered consistent with that possibility.

The body was subsequently cremated.

Whether the original conclusion was right or wrong is almost beside the point.

The tragedy is that future investigators, experts, lawyers and courts lost forever the opportunity to independently test that conclusion.

 If science is strongest when it can be reviewed, what happens when the evidence needed for review no longer exists, or when vital tests capable of confirming or disproving a theory were never conducted?

At that point, the issue is no longer whether the original conclusion was right or wrong.

The issue is that the opportunity to ever know may have been lost forever.

One of the greatest misconceptions in criminal justice is that scientific evidence speaks for itself.

It does not.

Science provides information.

Human beings interpret what that information means.

The distinction is important.

In an affidavit concerning DNA evidence in the conviction and appeal of R.D. McCartney, Professor John David Wetherall, Head of the School of Biomedical Sciences at Curtin University of Technology, stated:

"In my opinion, based on my knowledge and experience of DNA profiling, DNA evidence cannot solely be relied upon to draw conclusions about the role of a suspect in a crime."

This is not a criticism of DNA science.

Rather, it is a reminder that scientific evidence must always be considered alongside all the other evidence in a case.

DNA may help establish that a person was present.

It does not automatically explain why they were there, when they were there, or what role, if any, they played in an alleged offence.

The danger arises when scientific evidence ceases to be one piece of the puzzle and becomes the entire puzzle.

For many years, forensic scientists have been regarded as some of the most trusted witnesses in criminal trials.

Jurors often assume that scientific evidence is objective, impartial and beyond dispute.

In reality, scientific evidence is interpreted and presented by human beings.

A recent Western Australian case highlighted this uncomfortable reality. Public reports indicated that a forensic scientist who had played a significant role in an investigation had previously been dismissed for breaches of testing protocols and later acknowledged providing incorrect information to police.

The issue is not whether one individual made mistakes.

The issue is that entire cases can become dependent upon the perceived authority of experts.

When expertise becomes unquestionable, science risks becoming belief rather than inquiry.

Good science welcomes scrutiny.

It does not fear it.

When Expertise Extends Beyond The Science

Just as investigators can sometimes move beyond gathering evidence and begin defending theories, experts can occasionally move beyond reporting scientific findings and begin advocating interpretations.

This does not necessarily occur through dishonesty or bad faith.

Often it occurs because courts ask experts not only what they found, but what those findings mean.

The difficulty is that scientific findings and scientific opinions are not always the same thing.

A DNA profile, pathology report, or forensic examination may establish certain facts.

The expert's interpretation of those facts is a separate matter.

The danger arises when opinion gradually acquires the same authority as the underlying science.

At that point, juries, lawyers and judges may begin treating an interpretation as though it were an established fact.

This is not a failure of science.

It is a reminder that science and interpretation are two different things.

Where does science end and interpretation begin?

That single question sits at the heart of:

·      pathology,

• DNA evidence,

• blood spatter analysis,

• fingerprint comparison,

• arson investigations,

• and many wrongful convictions.

I do not believe science and interpretation can ever be completely separated.

Jurors need scientific findings explained to them. A DNA profile, pathology report or forensic examination is of little value unless someone can help the court understand its significance.

The challenge is not how to remove interpretation, but how to ensure that interpretation remains open to challenge.

One safeguard is to allow competing expert opinions to be presented where reasonable differences of interpretation exist.

In that way, the jury is not asked to accept a single interpretation as fact. Instead, they are able to consider alternative explanations and decide which is most consistent with the evidence.

The goal is not to eliminate expert opinion.

The goal is to prevent opinion from becoming unquestionable truth.

Justice or Victory?

Every prosecutor takes on an important responsibility.

Their duty is not simply to secure convictions, but to assist the court in achieving justice.

Most prosecutors genuinely accept that responsibility.

The question is not whether prosecutors intend to do justice.

The question is whether the systems in which they operate always encourage it.

Success is often visible.

Convictions are counted.

Cases won can be measured.

Career advancement, reputation and public confidence may all be influenced by outcomes.

Justice, however, is harder to measure.

A conviction may be recorded immediately.

The discovery of a wrongful conviction may take decades.

The danger for any institution is that it begins measuring success by what is easiest to count rather than what is most important to achieve.

If that occurs, the pursuit of justice can slowly become overshadowed by the defence of decisions already made.