Confusion in Court on LTDNA and LCN
The potential for misunderstanding of one Court following the judgment of another without the full knowledge of the facts and nuances that led to the published judgment are evidenced between the cases of Reed & Garmson in the Appeal Court in England and Wales, and the case of Wallace in New Zealand. This article illustrates how confusion has arisen and clarifies the issue with respect to Low Template (LTDNA) or Low Copy Number (LCN) DNA profiles.
The LCN Technique and stochastic effects
The LCN technique was designed to deal with very low amounts of DNA, a weight of less than 100 picograms (pg, a billionth of a gram, or 10-9g). DNA is present in samples as a number of discrete and different types of molecules of DNA (the alleles). The number of these molecules is related to the weight of DNA present in the sample. Each of the different alleles of DNA may not be present in exactly equal numbers, or may not be there at all. When the number of molecules is very low, the chemistry of the kit used to profile the DNA may not detect all of the molecules; some alleles may be better at being seen than others. In a series of tests on a sample at this level the results may be different for each test or run. This is a stochastic effect. It affects the reliability of the conclusions regarding the alleles that may be in the sample.
Confusingly, the same weight of DNA in different samples does not necessarily entail the same degree of stochastic effect; it depends on the ‘quality’ of the DNA (probably how much it is already degraded) and the performance of the analysis at the time of testing. However, experiments have shown that the expectation of stochastic effects increases dramatically as the amount of DNA in the sample reduces.
The English Appeal Court
The Appeal Court in Reed & Garmson sought to find a ‘safe’ amount of DNA for obtaining reliable results from LCN DNA profiling. It stated;
“(i) Low Template DNA can be used to obtain profiles capable of reliable interpretation if the quantity of DNA that can be analysed is above the stochastic threshold – that is to say where the profile is unlikely to suffer from stochastic effects ... which prevent proper interpretation of the alleles.” [my underline]
In other words, it is the presence of stochastic effects per se that renders the profile unreliable. We agree with that view.
For example, we have seen research results which showed a clear increase in dropout (a stochastic effect) at about 200pg of DNA (We are still bound by a confidentiality agreement that prohibits us from disclosing those results).
The Court judgment went on,
“(ii) There is no agreement among scientists as to the precise line where the stochastic threshold should be drawn, but it is between 100 and 200 picograms.
(iii) Above that range, the LCN process used by the FSS can produce electrophoretograms which are capable of reliable interpretation”.
It may have been because of Professor Jamieson’s acceptance that there was no defined point which could be called a stochastic threshold (even though the effect can be easily seen) that the Court sought to define a weight of DNA, which represented ‘safe’. Safe in much the same way that a defined speed limit may be easily measured but does not necessarily measure ‘dangerousness’ of someone’s driving even though that is the purpose of the limit – one may be under the limit and still dangerous. The DNA weight may suggest that the interpretation may be reliable, but it is the presence of stochastic effects regardless of the weight of DNA, that causes interpretational problems. This is widely accepted even by the proponents of Low Template techniques.
The debate is whether there is a solution to those problems that renders the interpretation reliable.
The Court’s conclusion that,
“... a challenge to the validity of the method of analysing Low Template
DNA by the LCN process should no longer be permitted at trials where the quantity of DNA analysed is above the stochastic threshold”
is, in fact, the ‘Pre-Reed’ position. We have not challenged the LCN technique when there is no stochastic effect. The only difference post-Reed is that the Court has now ADDED the condition that the safe area is above 100-200pgs, which to date has never been the issue of challenge.
The New Zealand Appeal Court
Turning now to Wallace, in which the Appeal Court in New Zealand was apparently informed by the judgment in Reed & Garmson:
In this case there was extensive dropout (a stochastic effect). The judgment stated,
“what is being advanced is a minority view (though undoubtedly sincerely held and on reasoned grounds) by a particular witness.”
The witness was Professor Jamieson of The Forensic Institute. The Court acknowledged his reasoning which was set out to them in very similar terms to his submissions to Reed & Garmson.
Nature, arguably the most prestigious scientific journal in the world, in March 2009, stated
“Low-copy-number analysis is accepted in just a handful of countries including Britain and New Zealand, but it is being applied in many cases.”
This clearly suggests that the opinion of Prof. Jamieson and The Forensic Institute is not a minority view. Indeed, the reason for the attention of Nature was the scientific controversy surrounding Low Template techniques.
The Court and the ‘safe’ limit
The NZ Court paraphrased the Reed & Garmson judgment,
“[97] … First, it is apparent that the Court of Appeal of England and Wales accepted that at least under defined conditions Low Template DNA can form admissible profiles, capable of reliable interpretation. …
Second, the Court of Appeal of England and Wales prescribed what might be called a “safety” floor limit. Above the range described by that Court as being a stochastic threshold of 100 and 200 picograms results can be so produced which are capable of reliable interpretation.
Third, in the view of that Court a challenge to the validity of the method of analysing DNA by the LCN process should no longer be permitted where the threshold limit is exceeded.” [our underline]
The Reed & Garmson defined conditions were, as explained, “above the stochastic threshold”. The weight of DNA is where that may be expected to occur – it is a secondary condition and not the primary one.
The NZ Court appeared to compound the stochastic threshold with a weight threshold. In an effort to establish whether the defined conditions had been met, at least as it understood them, the NZ Court then explored the issue of the weight of DNA, not the presence or absence of stochastic effects.
“In light of the observations of that Court we have endeavoured to determine whether the LCN analysis of the metal bar DNA in Wallace was above the stochastic threshold of 100-200 picograms discussed in Reed.”
The result of those inquiries was set out by the Court,
“[107] As we read the record, neither Dr Whitaker’s nor Professor Jamieson’s evidence detailed the quantity of DNA analysed in terms of picograms. …
[108] Dr Whitaker’s witness statement is dated 13 October 2006. That statement contains an Appendix 2 entitled “Summary of LCN DNA profiling results”.
However, that table only contains the DNA allele band types. It does not have a picogram count. In short, we were not able to locate in the trial file, or in the Case on Appeal, any picogram counts.
[109] Professor Jamieson’s statement of 5 April 2009 dealing with the DNA quantification in Wallace dealt with this matter somewhat obliquely:
“DNA is contained in cells. These cells are of the order of micrometres. About 10,000 are reckoned to be able to fit on the head of a pin. It is therefore entirely possible that the cells from different people, especially at the extremely low numbers involved in this case (evidenced by the clear stochastic effects in the DNA tests) could be expected to occupy different areas of the bar”.
[110] As we read this, there was therefore a reference to stochastic effects by Professor Jamieson but on what we had it was not clear whether these effects were occurring above or below the picogram threshold articulated in Reed.”
It should be noted that the ‘picogram threshold’ is in fact determined by, not a cause of, the ‘stochastic threshold’. Cause and effect have been transposed.
On that basis, the Court opined,
“It follows that Reed is of limited value in this instance.”
However, the record should presumably include Professor Jamieson’s statement to the Court on 24th February 2010 on that matter. He stated, unequivocally,
“There is extensive evidence of stochastic effects in the results obtained in this case.
The extent of those effects in my opinion strongly suggests that the amount of DNA in the samples is well below 200pg and well below any stochastic threshold above which the results could be considered reliable. ”
Understanding the challenge to LCN as scientific evidence
The NZ Court also discussed the nature and extent of the challenge being made to the LCN technique;
“[98] Mr King’s submissions in this case have not been entirely clear. Sometimes the argument seems to have been that LCN evidence should not be permitted at all, and sometimes that there are particular difficulties pertaining to such evidence in this case. In fairness to Mr King, much of this difficulty stems from the fact that the material filed by Professor Jamieson is still patently opposed to LCN evidence per se.”
Again, the limit of our attack was, as it has always been, exactly as defined by the English Appeal Court with respect to the presence and measurement of stochastic effects such as allelic dropout. Statements to the NZ Court (which also predate the Reed & Garmson judgment and evidence) in fact set out that position. Professor Jamieson’s statement of 24 th February 2010 to the NZ Court drew attention to the fact that his objections are limited, indeed to the very same objections apparently accepted by the Court in Reed;
“ln my statement of 22 nd September 2009 to this Court I stated ,
"l accept, and have accepted, that technology permits the amplification of very small amounts of DNA. I question the reliability of interpretations based on results that show clear stochastic effects...
I have dealt with several LCN cases where I have advised that there was no credible challenge to the results. But it cannot be argued that because reproducible results obtained with sufficient amounts of DNA using the LCN process have been accepted that this validates the use of the technique in circumstances where stochastic variability causes serious interpretational difficulties."
This has been my consistent position from my first studies of the LCN technique .”
Conclusion
The New Zealand Court acknowledged,
“ [114] There is certainly a “lis” between Dr Whittaker and Dr Harbison on the one hand and Professor Jamieson and Dr Geursen on the other. This Court is not in a position to say who, at the end of the day, is correct in a scientific sense. Then too, the science is moving on apace. This Court does not have the expertise, and in any event it is not ultimately the role of this Court, to come to any such determination.”
However, there has clearly been confusion regarding the cause of difficulties in the interpretation of LCN profiles (stochastic effects) and one of the parameters affecting those (amount of DNA). The material facts involved should not be in issue, but the availability of those facts may have differed for each Court. For that reason, it is important that those material facts should be made available to minimize the risk of future misunderstandings.
October 2012