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Writer's pictureMaryline

New uses of genetics in criminal proceedings.


"The evidence put to the test", headlined a daily newspaper shortly before the closing of the investigation of the Élodie Kulik case, in which the investigators had succeeded in identifying the attackers using a new technique: kinship research. Kinship research and the genetic composite portrait together illustrate the mutation known today by DNA which, for several years now, has become "the queen of evidence", today goes back to the time of investigation by becoming a real player in the process. In this context, genetics seems to take the lead in the investigation by giving impetus to its movement, especially when there is no clue to guide the investigations. The objective is to make the DNA “speak”, not only to prove a person's guilt, but to find the author of the offence. The main interest of these two techniques therefore consists in the existence of a predictive use of DNA.

In fact, it is a matter either, for the genetic composite portrait, of revealing the apparent morphological traits of an unknown person by an innovative process of DNA analysis, or, for kinship research, of identifying a unknown suspect by revealing the relationship he has with a person whose genetic profile is registered in the FNAEG, (National automated file of genetic fingerprints, instituted by law n° 98-468 of June 17, 1998 relating to the prevention and repression of offenses of a sexual nature.)

The genetic robot portrait thus demonstrates a new use of DNA (I), while research into kinship rather reveals an innovative use of the DNA database (II). In any case, the deepening of the respective study of these two techniques reveals, with a look abroad, that the genetic composite portrait and the research in kinship are ultimately, not proofs, but methods of investigation put to the test: of the risks they entail first of all, from a circumvention of the established legal framework to the underlying presence of discrimination; put to the test of an effectiveness which still remains to be demonstrated and which tends to call into question the need to consecrate and use these two methods of investigation.


By the way, without doubting the interest of the genetic portrait for investigators, its effectiveness remains in reality very relative. From a scientific point of view, the results of this expertise are currently unreliable. The analysis of certain markers leads to satisfactory results (eye and hair color) while others (height, age, corpulence) do not allow these characteristics to be predicted with a satisfactory degree of probability. These results do not in any way constitute a guarantee that the person does not present the indicated morphological trait. Moreover, being a genetic expertise, these results do not take into account the effects of epigenetics and the environment, nor the physical modifications chosen or undergone by the person. Alongside the genetic composite portrait, a new technique has recently been added to the investigation methods.


This is kinship research, which is a new use - just as controversial - of the national DNA file. Recently legalized in France, the technique of kinship research makes it possible to identify the author of the facts through one of their relatives, registered in the FNAEG. Mostly acclaimed by practitioners, this technique nevertheless involves, like the genetic composite portrait, many risks (A) for limited effectiveness (B).


The search for kinship confirms the modification of the initial purpose of the FNAEG. Initially designed to apprehend repeat offenders, it has seen its powers extend to allow the identification of individuals implicated, that is to say only suspected of having committed an offense.

Kinship research is part of this extension objective by allowing the use of the file for the purpose of apprehending a person whose genetic profile is not even listed within it. Beyond a diversion of the initial purpose of the FNAEG, this technique increases the inequalities of the criminal justice system.

The effectiveness of kinship research is theoretically subordinated to the importance of the content of DNA databases: the greater the number of genetic profiles, the more likely this technique is to reveal a partial match with one of the genetic profiles on file. The development of kinship research would thus stem directly from the expansion of DNA databases. However, practice invalidates these suppositions by demonstrating that the extension of the files, far from increasing the efficiency of the search for relatives, on the contrary weakens it by multiplying the number of partial matches revealed during the interrogation of the file. The increase in the number of genetic profiles listed in databases therefore leads to major identification difficulties.


Some French and American practitioners specify that more than a hundred partial matches can be discovered following a kinship search. The Nuffield Council on Bioethics, the equivalent of our French National Ethics Advisory Committee, notes that this extremely large number "seriously limits the usefulness" of this technique, in particular by leading to considerable and extremely costly investigations since each result should in theory give rise to several genetic expertises carried out on the relatives of the person on file, in order to identify the suspect. The large number of results obtained during a kinship search also demonstrates that several genetic profiles can cover certain similarities without being genetically linked.

Professor of Law at New York University, Erin Murphy thus specifies that “anyone who knows the science understands that there is a high rate of false positives” when it comes to family cross-checks or kinship research. The statistics reveal this very relative efficiency. Between 2004 and 2009, seventy requests for partial matches were made in Great Britain, of which only eighteen were successful, resulting in thirteen convictions. A 2014 British study also found that only 17% of family DNA searches “resulted in the identification of a relative of the real offender”.


This type of technique certainly makes it possible to sometimes elucidate unsolved violent crimes, but the aforementioned pitfalls discourage its practice.

In 2004, the British investigators would have resorted to only about twenty family cross-checks. In France, such statistics are difficult to establish due to the recent legislative consecration of kinship research. Several criminal cases have certainly been solved by the implementation of this technique, but prior to its apprehension by the legislator. Practitioners also appear relatively unconcerned by this new possibility of investigation. Many lawyers are not even informed of the existence of kinship research, which greatly reduces the possibilities of contestation.

A majority of magistrates affirm that they have not yet resorted to kinship research and limit themselves to noting the innovative and supposedly effective nature of this technique, without considering its potential legal or ethical consequences.


It is thus impossible to establish even the frequency with which kinship research is used. Is it systematically ordered, each time the DNA found at the crime scene does not correspond to any of the genetic profiles listed in the FNAEG?

Or, on the contrary, does it only intervene when there is no clue to support any line of research? In other words, is kinship research used as an ultima ratio, as a last resort, in case of absolute necessity? The answer to these questions is all the more important since kinship research is not only little known to practitioners: it is also known to the general public and individuals on file with the FNAEG, who are likely to be directly concerned by its implementation. There is no legal requirement to inform these people of the possible use of such a technique when their DNA is collected for the purpose of recording in the file. In other words, they are unaware that their DNA could possibly make it possible to confuse one of their relatives, if the latter were to commit an offense.


The British Nuffield Council on Bioethics has moreover raised this critical point by specifying that “the absence of consent relating to the use of the DNA on file to carry out family cross-checking makes this technique particularly sensitive. It is therefore important that it is only used if it is necessary and proportionate in a particular case”. In this context, one should either legally limit the use of this technique to unresolved offenses - which the legislator has not established, or, as the Nuffield Council on Bioethics recommends, "to carry out detailed and independent research on its operational usefulness and on the practical consequences that it generates on the persons concerned”. Such research - which should in theory be carried out before such an investigative technique is legally sanctioned - would make it possible, if not to call into question its necessary nature, at least to proceed to a general information of all the practitioners on the existence of kinship research and the risks it entails. Because it is perhaps this lack of information that constitutes the greatest risk in relation to kinship research.


The techniques of the genetic composite portrait and research in kinship strongly demonstrate that, benefiting from ever greater scientific progress, DNA has transformed the methods of investigation. Praised by investigators, these two new techniques risk, however, in addition to breaking down the legal barriers that have hitherto surrounded the use of genetics during the investigation, to open the way to methods of discriminatory and predictive investigation, for a very limited effectiveness. Highly unbalanced, the “benefit-risk” balance pleads for, at the very least, a real legal framework that would guarantee a necessary but also ethical use of these techniques.





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