The new law will help police to solve crimes,
as long as the DNA database is managed
correctly, according to a forensics expert.
Image: iStockphoto
A law passed in the New Zealand Parliament on 29 October will give police more freedom to take DNA samples, and is predicted to help solve a greater number of cases.
The change to the Criminal Investigations (Bodily Samples) Amendment Act will allow DNA samples to be taken from any person police intend on charging with an imprisonable offence from 2011.
Currently police can only collect DNA from those who voluntarily give samples, or people who are convicted of various serious offences (usually those punishable by seven years' or more imprisonment).
The new law will help to solve both current and unresolved (cold) cases, according to forensic science expert Dr Anna Sandiford.
"Cold case reviews in the UK have shown that successful matches can be obtained from people who have previously committed a serious offence and then more recently have to provide DNA and fingerprints in relation to minor offences such as traffic violations," she said.
Many criminals in the 1990s or earlier weren't aware that their DNA could be used to track them down and didn't think about what they were leaving at a crime scene, according to Dr Sandiford.
"Only the foresight of police and scientists meant that samples were collected and are now available for testing," she added.
At present there are around 100,00 DNA profiles held in the New Zealand National DNA Databank operated by Environmental Science and Research, and 8,000 of these related to unsolved criminal cases, according to the Ministry of Justice.
Dr Sandiford believes expanding this database will be beneficial to solving crimes, as long as it doesn’t become too large.
"At present, DNA and fingerprints are collected from everyone who is arrested in England and Wales, regardless of whether or not they are eventually charged. Concern has recently been raised in the UK about whether or not the DNA database has grown to be so big that interpretation is becoming problematic.
"Not only does the complexity of storing and searching such a large body of data increase substantially with the size of the database, but so too does the probability of errors, duplicates and false entries. Moreover, the chance of getting a false positive match is also much higher, simply due to the vast number of comparisons involved and the percentage of the population who have similar (or identical) DNA fingerprints."
Dr Sandiford said that it will be important for database users to understand and acknowledge any potential for error as the database grows.
"Experience in the UK has told them not to rely solely on DNA hits to successfully prosecute cold cases and I personally am always more comfortable with a multi-disciplinary approach to crime investigation."
Dr Sandiford added that in the future decisions may need to be made about when and what samples should be removed from the database, a matter which is currently being debated in the UK.
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