There have been significant scientific advances in the last 25-30 years since DNA  was first used in criminal investigations. For instance, over that time, scientists have discovered a huge amount about our DNA and genes and developed new techniques for analysis.

In 2003, after many years, and after spending nearly a billion dollars, the whole human genome was mapped by scientists – this is the map of the 3 billion base pairs that make up human DNA.

Now, for only about thousand dollars, someone can have their entire genome sequenced from a DNA sample.

In the health sector, the whole genome sequence of an individual can be taken with their consent in order to help doctors understand a person’s genetic makeup, in order to treat them, or for scientists to carry out research on particular diseases.

As scientists carry out more genetic research, they are starting to work out what particular genes do or might mean – for instance, whether someone has a certain cancer gene or is a carrier of a particular disease.

Scientists have carried out genetic research to work out which genes determine different aspects of people’s physical appearance. Enough research has now been carried out for scientists to be certain which genes indicate someone will have red hair or blue eyes, and which genes indicate certain ethnicities. However, other characteristics are more complicated to work out – like brown eyes or skin colour – as several genes are involved.

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) or what a person’s ethnicity might be. This prediction may be quite reliable if the person has the gene for red hair or other genetic markers that scientists can easily identify, but less reliable where scientists are not so sure what other genes might mean.

In New Zealand, scientists at the Institute of Environmental Science and Research (ESR) have, on a very few occasions, used these new scientific methods to analyse 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 Police authorise it. It is only done in serious cases as a last resort when all other avenues have been explored and exhausted.

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

It is important to be aware that ethnicity inference from a DNA sample is not necessarily the same as someone’s physical ethnic appearance. For instance, someone may look European/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, ESR does not currently do this.