Marie Allen – New methods for improved forensic and historical DNA analysis

The general objective of our research is to develop highly sensitive and discriminating assays for forensic DNA analysis of challenging samples.

Hand holding a micropipette
Photo: Marcus Marcetic

Evidence samples at a crime scene have often been subjected to harsh environments and may, therefore, have degraded DNA and can also be present in minute amounts. Our research involves the development of typing assays for analysis of mitochondrial DNA (mtDNA) as well as nuclear DNA (nDNA) markers. The use of mtDNA markers will allow a highly sensitive analysis due to a high number of mtDNA copies per cell. In addition, nDNA markers, amplified in very short PCR fragments, will yield a high discrimination power and Y-chromosome markers can allow resolution of mixed DNA samples (commonly seen in sexual assaults).

Analyses of challenging DNA samples

Several new assays have been developed in our research group and used successfully in the analysis of challenging evidence material in forensic cases. In a recent project, a combination of traditional methods and next generation sequencing (NGS) technologies will be evaluated for DNA analysis of degraded, limited and damaged samples.

Our NGS strategy is based on capture technology with high sensitivity and the design of a target panel with a large number of forensic markers. The protocol allows a uniform amplification of short nDNA or mtDNA targets to facilitate analysis of severely degraded DNA samples. The sequence analysis of the customised NGS panel on the MiSeq platform will result in simultaneous analysis of the entire mtDNA genome and over 900 autosomal markers (STRs, InDels, and SNPs).

A majority of the markers are forensically informative markers for individual identification, and a subset of the SNPs can be used to predict externally visible characteristics (EVCs) such as curliness of hair, freckle or eye, hair and skin colour. Predictions of appearance can be used as investigative leads to narrow the number of possible perpetrators in criminal cases without a suspect.

Historical investigations and casework analysis

As an ultimate test for success analysing challenging samples, has our novel methods been used in investigations of the putative remains of St. Birgitta and her daughter Katarina, Nicolaus Copernicus, Carin Göring, and the Swedish Warship Vasa. Even older remains are analysed in a larger collaboration project where samples from Viking age boat graves found at the island Salme in Estonia are under investigation.

We are also using the improved assays for casework analysis requested by the law enforcement and the national forensic laboratory. Moreover, our sensitive methods have proven valuable to identify the origin of cell lines used in medical cancer research recently.