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1.1 Summary
1.2 Implications
1.3 DNA Forensics in New Zealand
1.4 Links

 

 

Individuals normally have 23 pairs of chromosomes, comprising long strands of tightly woven DNA, which are collectively referred to as the human genome.  A complete analysis of the entire human genome is currently a time consuming and expensive undertaking, which is why a ‘DNA profiling’ approach is taken.  In forensic applications 15 specific sites within the human genome are analysed to help profile or identify individuals.  The variation at these 15 sites is enough to indicate there is a very high probability that an unknown sample came from the individual showing the same DNA profile.

 

DNA databases that contain DNA sequences obtained from crime scenes and from individuals such as convicted criminals are used as an investigative tool to help identify offenders and link individuals to crimes.  Countries vary considerably in their approaches as to who is included on such databases.

 

New techniques are emerging that enhance the ability to extract DNA from crime scene samples or enable more information about the source of a sample to be determined.   For example, Low Copy Number (LCN) analysis is used to obtain DNA profiles from touched objects that previously wouldn’t have been able to yield useable DNA samples.

 

Internationally, research is being carried out using DNA to determine a person’s physical characteristics.  In the US, a technique called ‘DNAWitness’, which examines 176 locations along the genome, has already been used in about 200 criminal investigations to identify the suspect’s ancestry.  

 

Future developments in DNA technology are likely to lead to even more sensitive methods for detecting and sequencing DNA. Increasing our understanding of the human genome and human genetic variation is also likely to provide genetic markers that yield more detailed physical and/or behavioural information about individuals.

 

 

 

Even though DNAWitness (see Section 1.1) is just another tool the police can use to narrow down their suspect list, it touches on race and racial profiling, which raises broader ethical questions about identifying a person’s ethnicity from their DNA.  Forensic applications of future developments in our understanding about human genetics (and also neuroscience) are likely to continue to stimulate discussion about the ethical and privacy implications surrounding the use of such technologies and the knowledge it generates.

 

Forensic DNA techniques, particularly new techniques such as LCN and DNAWitness, are currently expensive so the police need to ensure that DNA analyses are used only where they are most likely to provide vital information. As with existing DNA-based evidence, the newer techniques are likely to be subjected to very careful scrutiny by the judicial system. Very high standards of sample handling and processing will need to be maintained to exclude the possibility of contamination of samples, and appropriate data sets will be required to back up interpretation of the results.

 

Some of the DNA or RNA forensic techniques are also likely to be applicable to other areas where knowledge of genetic profiles is useful. For example, in biosecurity to identify pest organisms and/or their point of origin.

 

 

 

In the New Zealand criminal justice system DNA is collected and processed for two main reasons:

 

 

In New Zealand each crime scene is reviewed jointly by ESR and the police to decide whether LCN is used or not.  It is only useful if the article being examined is unlikely to have other individuals’ DNA profiles on it. 

 

Obtaining a DNA profile by LCN analysis is a more complex process than normal DNA analysis due to the risk of cross-contamination.  Samples are processed in an ultra-clean dedicated LCN laboratory and analysed by a core group of scientists with expertise in this area.  The costs associated with LCN are significantly higher than standard DNA profiling and elimination DNA samples need to be taken from investigating police and laboratory staff.

 

Although there are methods capable of identifying different cell types, these methods are limited and not always conclusive. To solve this problem, ESR is conducting research into the application of gene expression as well as proteomics to try and identify different cell types.  Different types of epithelial cells (buccal, vaginal, skin) display different proteins on the cell surface, which in turn can be identified by different genetic sequences.  ESR and the University of Auckland have developed a new method for identifying the different types of epithelial cells from protein profiles.  This technique has the potential to determine which part of the body cells have come from and may help to resolve points of contention.  For example, whether an object has cell types on it that would be consistent with a sexual assault.

 

In another example of forensic research being conducted in New Zealand, the University of Auckland’s departments of chemistry and biological sciences and the University’s medical school are jointly developing new ways of detecting nucleic acids.  They are developing organic polymers that can be used to identify DNA and specific sequences within the DNA. 

 

ESR is working on applications for such a technique; aiming to produce a device that a forensic scientist could take to the crime scene to deliver instant profiling.  The successful development of such a device would represent a significant advance on how forensic information is gathered. Currently, many samples have to be taken from a scene and processed in the lab - raising the risk of contamination or mixing of crime scene samples during transport as well as the health and safety implications associated with the transport of hazardous biological material,.

 

Another area of current research interest is ed on non-human genomics that will allow the unique identification of non-human material found at crime scenes.  Part of this work, being undertaken by ESR, is determining the feasibility of using microbial communities (which are unique to New Zealand) to determine a more accurate time of death for bodies and dismembered body parts.

 

 

 

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