Forensic statistics

Forensic statistics

Forensic DNA evidence is essential in modern societies to solve crime cases and legal disputes regarding paternity and family reunions. A central problem in these contexts is to calculate the evidential weight of the DNA evidence. This requires that the genetics and statistics of the DNA profiles are well understood. Modelling the genetic part of the evidence as well as the biotechn­ol­og­ical processes calls for statistical models.

When DNA evidence is used in crime cases, statistical models are crucial to account for various complex features of the data. It is for example needed to deal with mixtures of  DNA, allelic drop-out and/or degradation of the biological material. Other challenges are the introduction of newer and more sensitive biotechnological methods, e.g. sequencing, which means that models must be continuously improved and refined.

In some applications of forensic genetics, the genetic component is less well understood and fundamental problems need to be addressed. Lineage markers (i.e. Y-chromosome and mitochondrial markers) which are passed from generation to generation with no or few recombinations impose a challenge due to their structural form. Therefore research has focused on improving the understanding of these haplotypes in the Y-chromosome and mitochondrial DNA.

With more genetic markers becoming available through the introduction of DNA sequencing, methods for predicting phenotypes and physical appearance for investigative leads is being used more and more. Using genetic markers it is to some extent possible to predict features such as eye, skin and hair colour as well as age and ancestry.