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Laboratories conduct the enquiry

Genetic imprint:  a reliable method which is used more and more in criminal cases and paternity investigations.
Genetic imprint: a reliable method which is used more and more in criminal cases and paternity investigations.

For ten years now the police has had at its disposal a valuable tool to confound culprits: genetic imprints. In the past three years researchers of the European Stadnap project have been working on harmonising these identification techniques in order to make them more reliable and ensure that such forensic information can be exchanged between different countries.


A hair, a drop of blood, saliva or sperm are nowadays enough to betray someone. Apart from red corpuscles, all our cells contain DNA (deoxyribonucleic acid). From this molecule, which holds genetic information, scientists can today extract a biological identity card. The principle is based on genetic diversity which makes each living creature unique. While most genes are common to all humans, they are separated by hypervariable regions which differ greatly from one individual to another. In a matter of ten years this identification technique based on genetic imprint has become common practice in various types of enquiries, from criminal cases to paternity investigations.

A multitude of markers

To compile this particular identity card on the basis of a biological sample, the focus is usually on microsatellites, which are repetitions of DNA minisequences differing in size (referred to as Short Tandem Repeat or STR). In some cases, other types of markers are studied, for instance Single Nucleotide Polymorphism (SNP) of the genome.

Angel Carracedo of the Institute of Legal Medicine of Santiago de Compostella (Spain) explains that there is thus a considerable total number of genetic markers that can be analysed. In Europe, there are about 150 laboratories doing genetic tests. As there is no single test protocol, they do not necessarily study the same part of the genome to determine a genetic imprint.
This lack of harmonisation has a number of consequences. It complicates counter?opinions requested by courts when findings are contested but also the verification of the quality of work done by laboratories (an absolute condition before laboratories can be certified to compile DNA profiles). Lastly, and perhaps most importantly, the disparity of test protocols precludes all direct comparisons between various countries, which may considerably hamper investigations.

Need for standardisation

This lacuna has given rise to a research project launched in 1997 under the Standards, Measurement and Testing programme. The aim of the project is to harmonise genetic typing protocols both with regard to the regions studied and the techniques used. Known as Stadnap (Standardisation DNA Profiling), it provides a solid base for the work done in 1989 by fifteen European laboratories which informally pooled their efforts in the European DNA Profiling Group (Ednap).

The Stadnap partners have divided their work in a number of working parties. The first of these is carrying out a kind of technological survey and will publish a report on the various techniques used in the past ten years to determine genetic imprints. The second is selecting the reference protocols and markers to carry out these tests. To this end, all the participants take part in practical exercises to assess the quality and importance of each new marker and each test protocol. Hélène Pfitzinger, of the Codgene laboratory in Strasbourg, explains that in this way only reliable markers have been selected with which reproducible and the most explicit results can be obtained. On the other hand, those parts of the genome producing the most variable results have been eliminated. The selection criteria are the same for the techniques used.

The third and fourth working parties, finally, are responsible for the exchange of staff among the laboratories so as to promote technological transfer and study the databases recording the various markers used in European laboratories.

Various sources of DNA

Angel Carracedo points out that in this research there has been a special focus on analysing genetic markers of the Y chromosome, which is specific for the male genome. This is useful to study the cell mixtures and help to solve some cases of sexual aggression. In addition to studying markers on the DNA of chromosomes, the researchers also studied the DNA of mitochondria, the energy centres of cells. The Stadnap coordinator notes that when DNA of the cell nuclei is degraded or absent from the sample - in particular in hair and bone - mitochondrial DNA may be analysed which is better protected than nuclear DNA and it is therefore easily found in a poor quality sample. This aspect is becoming increasingly important in legal medicine.

However, genetic imprints derived from mitochondrial DNA are hard to interpret and special caution is in order when handling this DNA. The project partners have therefore worked out precise standards for the use of this type of DNA for identification purposes.

The endeavours at standardisation at European level need not stop there. New genetic markers and new typing techniques are constantly developing, for instance DNA chips. The continuation of European cooperation is of particular importance as various countries - United Kingdom, Netherlands, Germany, France, Austria - are compiling national genetic imprint files, which could eventually form the core for a joint database.

Standardisation of DNA Profiling in the European Union

Standards, Measurement and Testing

SMT4 CT97-7506

Angel Carracedo
"San Francisco" Institute of Legal Medicine
15705 Santiago de Compostella
Fax : +34-981 580336
E-mail :

- Institute of Legal Medicine, Santiago de Compostella, Spain (coordinator)
- Institut für Rechtsmedizin, Universität Mainz, Mainz, Germany
- Institut für Rechtsmedizin, Münster, Germany
- Bundeskriminalamt, Wiesbaden, Germany
- Hellenic Police, Forensic Science Div., DNA Laboratory, Athens, Greece
- Forensic Science Service, Birmingham, United Kingdom
- St. Bartholomew's and the Royal London School of Medicine and Dentistry, London, United Kingdom
- Institut National de Criminalistique, Brussels, Belgium
- Instituto de Medicina Legal, Coimbra, Portugal
- Retsgenetisk Institut, Copenhagen, Denmark
- Forensic Science Laboratory, Dublin, Ireland
- Institut für Gerichtliche Medizin, Innsbruck, Austria
- National Laboratory of Forensic Science, Linköping, Sweden
- Rettsmedisinsk Institutt, Oslo, Norway
- Direction de la Police Judiciaire, Laboratoire de Police Scientifique, Paris, France
- Institut de Médecine Légale, Strasbourg, France
- Gerechtelijk Laboratorium, Rijswijk, Netherlands
- Istituto Medicina Legale, Universita Cattolica, Rome, Italy
- National Bureau of Investigation, Crime Laboratory, Vantaa, Finland
- Asham Pharmacia Biotech, Barcelona, Spain
- Perkin Elmer Applied Biosystems, Foster City, United States

In Europe, there are about 150 laboratories doing genetic tests. As there is no single test protocol, they do not necessarily study the same part of the genome to determine a genetic imprint.