DNA advances raise questions for criminal investigations

Publication Date 
04 August 2017

DNA science has advanced exponentially in the last three decades since Police first used DNA in criminal investigations.

Scientists can find out a lot more information about us from our DNA.

For instance, scientists are working out which genes determine different aspects of people’s physical appearance. They know which genes indicate someone will have red hair or blue eyes, and which genes indicate certain ethnicities.

In some countries, scientists are using this sort of genetic research to analyse DNA samples from a crime scene in order to predict what a suspected offender might look like (in one case even developing an identikit picture from this) or what a person’s ethnicity might be. 

In New Zealand, scientists at the Institute of Environmental Science and Research (ESR) have, on a very few occasions, used a DNA sample from a crime scene to find out the probable ethnicity of the DNA owner (who may be the offender).

ESR will only carry out this analysis when the police authorise it. It is only done in serious cases, when all other avenues have been explored and exhausted.

Police used this technique to determine the likely ethnicity of DNA found in the 2010 homicide of the taxi driver Hiren Mohini.

Inferring ethnicity from a DNA sample is not the same as inferring someone’s physical ethnic appearance. For instance, someone may look Caucasian but have, for instance, Asian or Polynesian ancestry as well.

ESR could also use these scientific methods to analyse a DNA sample from a crime scene to find out other genetic markers, such as hair or eye colour, or even a rare disease. However, it does not currently do this.

The Law Commission's review of the Criminal Investigations (Bodily Samples) Act 1995, which governs how the police and scientists use DNA in criminal investigations, will consider these new scientific advances.