LCN DNA Analysis and Opinion on Transfer: R v Reed and Reed
| Published date | 01 April 2011 |
| DOI | 10.1350/ijep.2011.15.2.375 |
| Date | 01 April 2011 |
| Subject Matter | Case Note |
LCN DNA ANALYSIS AND OPINION ON TRANSFER
CASE NOTE
LCN DNA analysis and opinion on
transfer: R v Reed and Reed
By Allan Jamieson*
Director, The Forensic Institute
Keywords
LCN; DNA; Transfer; Scientific opinion; Stochastic effects
ow Copy Number DNA (LCN) analysis has acquired a high profile in
forensic circles, but has gained more attention following judicial
L criticismofthetechnique’sreliabilityintheOmaghBombtrial,RvHoey.1
The judgment in Hoey was quickly followed by a review conducted on behalf of the
new Forensic Regulator (Caddy Review),2 which gave the technique an apparent
clean bill of health. However, the conclusions set out in the review have attracted
criticism3 and have not led to agreement about the general use of LCN analyses.4
The judgment of the Court of Appeal in R v Reed and Reed5 deals with two issues. The
first is the admissibility of evidence of this type of analysis. The second, and
perhaps more contentious, issue concerns whether an expert witness ought to be
permitted to provide an opinion as to the likelihood and means by which DNA
might have been transferred to the place where it was discovered.
*
Email: allanj@theforensicinstitute.com.
1
[2007] NICC 49; see R. Pattenden, Noticeboard, ‘Integrity of DNA Evidence—United Kingdom’ (2008)
12 E&P 169.
2
B. Caddy, G. R. Taylor and A. M. T. Linacre, A Review of the Science of Low Template DNA Analysis (2008),
available at
3
J. Gilder, R. Koppl, I. Kornfield, D. Krane, L. Mueller and W. Thompson, ‘Comments on the Review
of Low Copy Number Testing. Letter to the Editor’ (2008) 23 Int J Legal Med 535.
4
B. Budowle, A. J. Eisenberg and A. van Daal, ‘Validity of Low Copy Number Typing and Applications
to Forensic Science’ (2009) 50 Croat Med J 207.
5
[2009] EWCA Crim 2698, [2010] 1 Cr App R 23.
doi:10.1350/ijep.2011.15.2.375
THE INTERNATIONAL JOURNAL OF EVIDENCE & PROOF (2011) 15 E&P 161–169
161
CASE NOTE
The technique’s proponents claim to obtain reliable DNA profiles from amounts of
DNA well below the amounts recommended by the manufacturer of the kits that
are used to produce reproducible STR profiles.6 STR stands for Short Tandem
Repeats. These are short lengths of DNA that have, during evolution, become
linked like the carriages of a train—tandemly. We inherit one set of carriages from
each parent at each DNA area (locus). There are ten loci that are analysed in the
United Kingdom, plus one that identifies the gender of the person. The different
lengths of DNA are called alleles. So we each have two alleles (one from each
parent) at each locus (area). DNA profiling is essentially the process of identifying
the alleles at each locus of an individual. In standard DNA profiling the process
uses enough DNA to produce the same result every time the sample is analysed.
For that reason, it is normal in standard profiling only to run the sample once.
The problems begin when the results from the analyses of ostensibly the same
biological material obtained from crime stains produce quite variable results. The
variable results are the consequence of a sampling phenomenon called a
‘stochastic effect’ or stochastic variability. A stochastic effect is a random variation
expected when analysing a sample from a very small population.
To appreciate what a stochastic effect is, consider if you ask only 10 people what
team they support. You are unlikely to get an answer that reflects the views of
the whole population. Ask another group of 10 people and it is likely that you
will get a different result. The sample size of people is too small to gain a reliable
representation of the overall population’s team loyalty. Indeed, two small
samplings of team supporters are likely to give two different representations of
team loyalty. However, ask 10 million people and you are more likely to obtain a
more accurate picture of the true number of supporters of each team. The
stochastic effect is evident in the difference in results between the two samples
of 10 people.
In LCN profiling, a particular example of one of the methods of Low Template
profiling (the template being the DNA material that one has at the beginning of
the profiling process), there are so few molecules of DNA available in the sample
that these random or stochastic effects appear. Critics of the technique7 contend
that this renders interpretation unreliable as a measure of what is in the sample.
Proponents assert that the difficulty can be surmounted by counting only alleles
6
P. Gill, J. Whitaker, C. Flaxman, N. Brown and J. Buckleton, ‘An Investigation of the Rigor of
Interpretation Rules for STRs Derived from Less than 100 pg of DNA’ (2000)
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