An interesting but slightly unsettling new use for genetics is beginning to emerge. There now exist companies that are offering to provide law enforcement agencies with a computer generated image of a person’s face based solely on their DNA. For me, the problem with this would be that we simply don’t have the knowledge to be able to do so.
Below you can see an example of the report produced by one such company, Parabon. The picture is supposedly of a sex offender from Florida that has been preying on women for more than two years. No one has ever seen him, his face is always covered, but he does leave DNA samples behind and these are what has been analysed.
The report gives five main pieces of information: ancestry, skin colour, eye colour, hair colour and the presence of freckles. In this case they predict that the individual is mostly Latino in heritage and, therefore unsurprisingly, that he has brown eyes, black hair and no freckles. They have no idea how old he might be and so they have shown a person in their mid-twenties for illustrative purposes.
It isn’t completely unreasonable to say what somebody’s ethnicity is based on their DNA. You can say what percentage of their genome comes from which type of background, but I think it is far more of a leap to say what that means they will look like. You can refine your prediction by looking at some of the known genes for eye, hair and skin colour but for the majority of people this won’t be especially helpful. Most such genes remain unidentified despite out best efforts. Those people who are very dark or very fair can be identified without too much difficulty, but for the masses who are generally somewhere in the middle it really is guess work. All except the gingers that is, you can genetically spot a ginger as easily as you spot one at the beach slathering themselves with SPF 5000.
The people trying to sell this technology, to be fair to them, aren’t telling anyone that they can predict exactly what a perpetrator will look like. They argue that it is more for saying what they won’t look like. In our example here, they can say with a high degree of confidence that it isn’t a black or asian guy, and that he doesn’t have blue eyes or ginger hair. These are fair statements that can be made with a high degree of confidence and potentially would have some use in the filed for detectives; so the technology is not completely without merit.
As far as specific features of the face go; nose size and shape; angle of the forehead; how far apart the eyes are and so on; any attempt at detailing these would be a complete work of fiction. There simply isn’t the data in existence to even begin to do that. Even with height, one of the most studied traits of all time and one which we know to have a strong genetic component determining it, there is no way we could be any more accurate than 3-4 inches based solely on an analysis of their DNA.
So how much use is this? I guess that will be up to individual police departments to decide. As long as everyone goes in with their eyes open knowing exactly what can and cannot be determined with accuracy then it wouldn’t be any more or less harmful than a description given by a traumatised witness based on half a glimpse of someone’s face. Remember, though, that grave miscarriages of justice have been committed on far less sturdy information.