Challenges of DNA before New Zealand courts

Helen Roebuck DNA expert giving evidence

The R v Wells conviction contains scientifically problematic features, most notable was a novel concept around “fragile sperm”, in support of possible sperm, when it was concurrently acknowledged that no sperm had in fact been detected.

The expert acknowledged that there was no data supporting the theory.

Such speculation by experts at hearing are consistent features of known DNA wrongful conviction Fitzgerald v R – why it can happen again.

Roebuck Forensics proffers DNA expert witness testimony regarding serious criminal matters. Our experience spans decades and more than 1,000 matters before the courts including murder, sexual assault, explosives, firearms and class A drugs

In 2014, the Appeal against the conviction of Tony Russell Wells was dismissed before the High Court of New Zealand.

There are evidentiary and scientific factors pertaining to R v Wells [2012] which are problematic and are consistent with identifiable aspects of known DNA wrongful convictions.

In some respects, the conviction itself is perhaps broadly seen as uncontroversial, whilst certain aspects of the matter have found relevance within the scholarly and New Zealand political arena, pertaining largely to the retention of DNA testing results and associated evidentiary material.

The 2012 conviction of Mr Wells in the Palmerston North District Court on one count of sexual violation and one count of sexual connection involving anal penetration, relied with some significance upon the DNA evidence.

In setting out its conclusion, the High Court reasoned;

“ The combination of the DNA evidence, the fingerprint evidence and the propensity evidence of the very similar offending against S meant the Crown case was compelling. The combination of coincidences required to bring about a situation where the appellant’s DNA and fingerprints were both wrongly associated with an offence very similar to one he committed in a similar location made the circumstantial case a strong one.”

Defence Expert Evidence

At first instance, defence did not rely upon an expert witness in response to the scientific evidence tendered by the prosecution.

Upon appeal of the conviction, the defence put on a concerted effort to bring in expert witness testimony.

This belated effort was met by the High Court as follows;

As we pointed out to Mr Hewson at the hearing, the time for a defendant to advance his or her defence is at a trial, not at an appeal”.  [1]

“ It is clear that Mr Doyle’s [defence expert] evidence is not fresh, in that it was obviously available at the trial. But we admitted it on a provisional basis so that we could address the arguments Mr Hewson wished to make in support of the appeal in relation to the DNA evidence”. [1]

In my experience, the absence of defence expert witness testimony is common to the vast majority of DNA wrongful convictions.

Prosecution Expert Evidence

The prosecution relied upon DNA expert testimony from a senior analyst at ESR, which was relevant to multiple samples contained in the medical examination kit (MEK).

Significantly,swabs taken from the mouth, cervix and vagina of the complainant did not show any spermatozoa on visual inspection and were not tested further” [1], and seemingly not submitted to ESR.

The allegations of this matter involved the complainant being stripped naked, followed by actual and or successfully resisted penile penetration of all orifices. Further, the accused was said to have ejaculated upon the complainant’s chest, and subsequently wiped down using tissues, which were recovered by police, along with a used condom in the vicinity of the incident.

I find it highly irregular that the absence of visually apparent spermatozoa, could lead to a decision to not send samples for scientific testing. The presence of spermatozoa (sperm cells) cannot be determined by visual inspection. Even should it have been the case that “visual inspection” meant microscopically, it does not at all conclude whether semen is present in the absence of sperm cells (which is a possible outcome). Furthermore, the identification of DNA is by no means contingent upon the presence of spermatozoa. The defendants, or indeed other persons, DNA may have been recoverable from those samples of which a decision was made to not test.

The information on the untested samples, even the absence of the accused’s DNA, is information that is valid, relevant and of significance to the court.

Separate to the untested samples, the anal sample was tested and returned no results, with the chest sample subsequently becoming the focus of DNA evidence before the court;

“Analysis showed that a semen-stained swab taken from the complainant’s breast area contained DNA that was 90 million times more likely to have originated from the appellant than from any other unidentified male selected at random “  [1]

A significant issue for scientific consideration with the chest sample, given the allegations, is whether semen is present. This consideration can be assisted by analysis as to whether the DNA originated from sperm cells, or another cell source.

There were two possible scientific explanations for the court to consider regarding the cellular origin of the DNA. One being that the DNA originated from sperm cells “The other was that the DNA was in fact from another cellular source (for example, saliva) “[1], as the prosecution expert correctly stated.

The ESR expert was cross examined in an effort to resolve the question over whether the DNA originated from sperm cells (spermatozoa);

“Q. So just to round up doctor [sic], I wish to reiterate two points, no DNA was found from spermatozoa from any of the samples you examined in this matter?

A. The DNA profile we obtained was in the epithelial fraction, I can’t tell you if it was, the, if the DNA was from sperm or not from sperm.

Q. But you can say the sperm was extracted from the sample and made into a sub-sample?

 A. Yes that’s correct. Because of the age or the time delay, six or seven years, it is possible that the sperm have become more fragile and have broken apart earlier than would be expected and therefore the DNA has been released into the epithelial fraction, so it is, it is either that that the DNA profile is from the sperm but is in the epithelial fraction or alternatively it could be that that, that DNA is from another cellular source that isn’t sperm.”

The High Court seemingly did not accept the prosecution expert’s multiple statements that the DNA could have originated from a source that is not sperm, when it made reference to the semen – stained swab.

Firstly, it must be stated that there is nothing in the judgement, that establishes the presence of semen or sperm cells scientifically. The usual process taken would have included chemical screening for seminal fluid and a microscopic inspection of the sample to identify sperm cells. A further process that is best practice would involve making additional microscopic slides during the DNA analysis process from the two fractions to determine whether sperm is present within the sperm fraction.

In this matter, the DNA evidence suffered continuity and quality issues, as a consequence in part of the discontinuance of proceedings closely following the incident in 2003. Whilst these quality factors are not necessarily attributable to ESR processes or any failure on their part, those factors do and should impact the scientific evidence, assessment and interpretation.

Whilst the scientific discussion in cross examination around “fragile sperm” follows a somewhat theoretically possible path, it is a novel concept.

To put this concept into context, it is something I have never heard discussed, seen written, nor evidenced over the last 25 years of forensic DNA development.

From what I see in the judgement, and the ESR expert’s responses, the DNA could be from any cell type, including saliva or skin cells, and rather, there is nothing to suggest that it is from sperm.

“She was then asked whether there was any statistical research about the possibility of the fragile sperm explanation being correct. She said there was no statistical data on that.” [1]

An expert theory or opinion must be formulated through the understanding of an identifiable body of knowledge that is evidenced and available for auditing.

 “ an expert witness must “explain the basis of theory or experience” upon which the conclusions stated are supposed to rest, for, as Sir Owen Dixon said in an extra-judicial address quoted by Fullagar J, “Courts cannot be expected to act upon opinions the basis of which is unexplained”. [2]

Significance of R v Wells

The DNA in context of the gamut of evidence, may or may not have contributed significantly to the outcome of this matter.

However, the DNA evidence as presented could undoubtedly contribute significantly to the outcome of a matter, should similar DNA evidence be presented and go unchallenged at first instance, as was the case here.

Of significance is the manner in which the chest sample was dealt with at hearing.

DNA is highly transient and can be readily transferred by mere touch, making the presence or lack of semen a critical factor for consideration with the specific allegation.

There is nothing in the judgement that leads to a scientific conclusion that there was semen or sperm cells, perhaps only the allegation, and resultant hypothesis that was relied upon whilst interpreting the sample.

The novel scientific explanation that was proffered in support of the semen hypothesis, was acknowledged to be formed in consideration of no statistical data.

The High Court was seemingly persuaded nonetheless, when referring to the “semen-stained swab” in the judgement. [1]

Verbal scientific opinion at hearing

The insertion of unsupported verbal opinion at substantive hearing is common and can be highly prejudicial to the courts, even more so with juries.

Regularly these opinions are proffered as weightings in support, such as “more likely” or “most likely” etc.

In this case the verbal opinion forwarded an alternate and novel scenario to attribute the origin of the DNA to sperm cells, which perhaps obfuscated the paramount question before the courts as to whether there was semen at all.

In response to this opinion evidence, the court seemingly preferred to decide that there was semen.

These opinions not coming to light in advance of substantive hearing, can be difficult to deal with, particularly should the defence not have an expert to adequately consider and respond to the opinion.

I have found that drawing out crown expert opinion evidence through a process of proffering written expert opinion, and the utilisation of Voir Dire, can bring these opinions to light in advance of substantive hearing.

With these crown expert opinions set out openly in evidence, they can be adequately and appropriately dealt with through defence expert testimony at substantive hearing.


1 – Wells v R CA517/2013 [2014] NZCA 479

2 – Makita (Australia) Pty Ltd v Sprowles