Seifeddine v R: DNA Evidence of the Accused Was Found on the Trigger of a Gun.
Case closed? Not quite.
Case Background
Mr Seifeddine was a part-time worker at a cafe where a search warrant at the premises located a number of firearms held in a bucket, which had been secreted in a wall cavity. DNA matches for Mr Seifeddine were found in various places, including on the rim of the bucket and on the trigger of one firearm, which had been wrapped in a sock.
Seifeddine v R [2021] NSWCCA 214
Initial Outcome
Mr Seifeddine was initially convicted of firearm possession in 2019, with some of the critical evidence in this matter being the trace DNA on the bucket and firearm, as well as CCTV evidence of him accessing the wall cavity.
Challenging the DNA Evidence: Secondary Transfer and the Fallibility of DNA Matches
The simple fact that needs to be clearly understood is that the presence of DNA on an object does not offer an explanation for how the DNA came to be there.
A person who regularly enters any space, as Mr Seifeddine did as a part-time worker who frequently accessed the area around where the firearms were hidden, will ‘shed’ DNA in multiple places and in multiple quantities, including shedding more where friction is involved, such as twisting door knobs or opening buckets (like the one the firearms were held in).
This DNA can be transported around the space by anyone who, for example, touches the same door knob or opens the same bucket. Various factors can also affect the DNA transfer, including the porosity of materials, with some materials transferring DNA more easily than others.
Secondary Transfer Opportunities Across Time
Image courtesy of Misleading DNA Evidence: Reasons for Miscarriages of Justice by Peter Gill.
The Scientific Case Against the Conviction
In order to form an opinion on how DNA could be deposited, there is a mechanism known as activity level assessment that can be performed. This, like the likelihood ratio, requires the formulation of two propositions to evaluate. Scientific data is then used to inform these propositions and calculate a likelihood ratio.
When it comes to the deposition of trace DNA (that is, DNA that cannot be attributed to a biological fluid), it is extraordinarily difficult to find sufficient and applicable published data in order to calculate some form of probability to provide an opinion on how the DNA was deposited.
Experimental data has also demonstrated that neither the quantity of DNA recovered nor the quality of the DNA profile obtained can be reliably used to determine the nature of deposition, i.e., direct or indirect DNA transfer. This is due to the transfer, persistence, and recovery of trace DNA on/from persons and/or objects being a highly complex and multifactorial process, as outlined in the image above.
Outcome: Conviction Overturned Due to Possibility of Secondary Transfer
At first glance, the DNA evidence, particularly matches appearing on the trigger of the gun, is conclusive evidence. However, careful analysis of the collection of the evidence, which was recorded by police, showed enough opportunities for secondary contamination to occur that the ruling was quashed. These included:
- The police gathering evidence using the same pair of gloves despite touching numerous surfaces.
- The possibility that the DNA match on the rim of the bucket was a result of Mr Seifeddine previously opening the bucket as part of his day-to-day responsibilities.
- The possibility of Mr Seifeddine’s DNA being on the sock which held the gun through some other means, and this being transferred to the gun (as the sock is a highly porous material), including the trigger, while being pulled out by the police.
The Conclusion
DNA evidence is not fallible. It merely provides a probability that DNA found on an object may have originated from an individual. Unless a very specific evaluation has been conducted to inform at an activity level (a contentious practice for trace DNA), this probability remains uncertain.
When seeking or challenging a conviction based on DNA evidence, it is imperative that any limitations to the evidence are reviewed thoroughly, and any expert witnesses involved clearly outline them to ensure the court is able to appropriately evaluate the evidence.
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