Distraction Free Reading

Interview: Corinna Kruse on the Social Life of Forensic Evidence

In The Social Life of Forensic Evidence (UC Press, 2015), Corinna Kruse traces how Swedish forensic scientists remove objects and traces from a crime scene, transforming them into evidence in labs and through interactions with court officials. This is a story of how evidence is made in anticipation of court procedures, and how in the process, different actors deal with the vulnerabilities inherent to this making. Interview by Ilana Gershon.

Book cover for Corinna Kruse's The Social Life of Forensic Evidence; grid of multicolored rectangles with enlarged images of fingerprints.

Ilana Gershon: How did you get the idea to study forensic evidence and how it circulates from crime scene to court?

Corinna Kruse: It was from a curiosity that grew over several years, first sparked off by a rather off-hand remark from one of my interlocutors in a previous project. Then, I was studying genetic research practices and was intrigued by how painstakingly and carefully the laboratory staff managed uncertainty—uncertainty being inevitable when dealing with biological material. She said if I thought they were being careful, I should see how the people at the Swedish National Laboratory of Forensic Science worked; there, someone was always sitting next to the person doing an analysis to make sure that they didn’t make any mistakes.

That image stuck with me and gradually turned into the idea of looking at practices of dealing with the (inevitable) uncertainty in a context where consequences, and in particular the consequences of making mistakes, are immediate and tangible. Of course, mistakes are undesirable in a research laboratory, as well, but mistakes in a forensic laboratory also affect people’s lives as well as trust in the criminal justice system. This applies particularly when, like in Sweden, there is only one forensic laboratory and that laboratory, in addition, is run by the state. From there, it wasn’t far to wanting to look at how the criminal justice system as a whole provided the forensic evidence with legitimacy and credibility throughout its journey from crime scene to courtroom. That brought in turn with it an interest for whether and how forensic evidence is kept from losing its meaning when moving through the criminal justice system’s different epistemic cultures. So, this project has gradually grown away from its seed—but I’m still grateful for that remark.

IG: So much of the work of crime scene technicians involves producing inscriptions, transforming the traces found at a crime scene into a report that then circulates. Could you talk a little about the differences between scientific reports and forensic reports—how crime scene evidence in state laboratories differs from scientific evidence in academic laboratories through the practices of inscriptions?  

CK: To point out the similarities first: both strive to transform something material—and often messy and transient—into a more manageable form. The symbolic shape seems to fit much better into both scientific and forensic practices. Perhaps that is not surprising; both are concerned with credibility and legitimacy.

One important difference is that the inscriptions made in forensics are not meant to be combined in the same way as those made in scientific research. Forensic inscriptions are meant to be combined with other inscriptions in the same case—crime scene reports, expert statements, interrogation reports, both past, present, and future—but they are not meant to be combined outside of the case. This has, of course, to do with different objectives: scientific research is aimed at producing generalizable knowledge about the world, whereas forensic science is aimed at producing knowledge about particular cases. (Simon Cole has written very insightfully about science and forensics.)

That does not mean to say that there is no research or development in forensic science—there is, of course—but for forensic innovations to be used in casework, they must be perceived as proven and dependable. US readers may think about admissibility hearings now, but in Sweden, there is freedom of evidence, which means that any evidence is admissible in court. However, as pre-trial investigations must be impartial, it is a matter of professionalism for forensic scientists and crime scene technicians to produce reliable evidence; not experimenting in investigations is part of that professionalism.

Another difference is that, because forensics makes particular knowledge about a particular event, it is also finite in ways that research science isn’t. Scientists are always (at least theoretically) able to perform more and perhaps different experiments to build up their knowledge claims, but for forensic science, all there is is what the crime scene technicians recover and the forensic scientists analyze. If there are too few traces or the traces get damaged, nothing more can be done.

Likewise, a pre-trial investigation leader may have to decide between mutually exclusive analyses, and once the analysis is done, there is no going back. So, forensic reports can be incomplete in a way scientific reports would not be: there just may not be anything to be done about the gaps.

That also means that reproducibility, which is one of the yardsticks for research science (at least in theory, the practice can be a bit more complex), is not attainable in forensic science. Which leads us back to the question of legitimacy: in forensic science, this is a slightly different issue than in research science.

IG: You discuss how crime scene technicians mediate between different epistemic cultures, à la Karin Knorr Cetina, in doing their work—transforming a crime scene into forensic evidence that can bolster certain legal stories in court. Yet in some sense, everyone hired by the state at a crime scene is moving between different epistemic cultures. I was wondering if there is something distinctive about how crime scene technicians act as translators as opposed to cops or lawyers?

CK: Of course you’re right—working in the criminal justice system always entails a measure of dealing with different epistemic cultures. What distinguishes crime scene technicians from other members of the criminal justice system is both their background and their expected role.

Through their background, crime scene technicians have insight into several epistemic cultures: they start their careers as regular police officers, with training from the police academy and subsequent experience of uniformed police work. Many have also worked as investigators before transferring to a crime scene division. There, they are introduced to crime scene work before going to the Swedish National Laboratory of Forensic Science for a course (half a year’s coursework spread out over a year) in forensic science. That course is directed towards crime scene examinations, but it also gives the participants insight into the epistemic culture of the laboratory. That is, they meet forensic scientists in the classroom and during exercises and breaks, and they get a glimpse of how forensic scientists think about and work with forensic evidence. Half a year of exposure to the Swedish National Laboratory of Forensic Science might not sound like terribly much—even though that time is packed with lectures and exercises—but it still gives them an insight that is different from that of the other professions. It also gives them the personal relationships with forensic scientists that may make it easier to call the laboratory and ask for advice or discuss a difficult case.

In addition, crime scene technicians are expected to play a mediating role in a way that others aren’t. They are, for example, expected to counsel leaders of pre-trial investigations on how to use the forensic laboratory efficiently (as opposed to swamping them with orders), or to give advice on which analyses can be performed to benefit an investigation.

Thus, crime scene technicians are both reasonably fluent in different epistemic cultures and quite used to moving between them. And that, I think, makes all the difference. Members of other professions are of course aware that there are epistemic differences—although they would probably not put it in these terms—but from what I have seen, they don’t seem to code switch as easily. I suspect that there is also a status dimension to who does most of the mediating—prosecutors and forensic scientists have academic backgrounds, whereas the police is traditionally blue-collar—still, crime scene technicians mediate much more facilely than, say, police investigators, at least between the criminal justice system’s epistemic cultures. (As everyone who comes in contact with those involved in investigations—plaintiffs, suspects, witnesses—also meets their expectations from criminal justice they, presumably, do their own kind of mediating between the public and the criminal justice system.)

So, crime scene technicians are the designated and, to a degree, trained translators, and as such they play a distinctive part in making the criminal justice system’s cooperation on forensic evidence possible. In fact, I think their contribution is often a bit overlooked—examining crime scenes, while certainly important, is only one aspect of their work.

IG: You suggest forensic evidence circulates as a semi-transparent box, instead of moving like objects that STS scholars are more familiar with: boundary objects, black boxes or immutable mobiles. Could you explain a bit more about how you are conceptualizing a semi-transparent box and discuss what network or institutional conditions might have to be in place to produce semi-transparent boxes?

Perhaps I should start with a confession: I am at least as much of an STS person as I am an anthropologist (perhaps you’ve guessed?) and the STS part of me is really fascinated with the question of how to think about the movement of knowledge.

So, what I find interesting about forensic evidence is that it both does and doesn’t quite fit into existing STS notions of knowledge objects. That is, forensic expert statements are meant by both their authors and their recipients to be stable; stability is, after all, central to legitimate and credible forensic evidence. And, in STS understandings, the most dependable way to keep facts (and artifacts) stable is to black box them, to package them in a way that their users neither need nor can concern themselves with such things as mechanisms and practicalities. The less room for interpretation or tinkering there is, the more the (arti)fact will look exactly the same in the hands of the user as it did in the hands of its maker. In addition, black boxing makes the (arti)fact more movable: one is not required to understand how a cell phone works to be able to use it.

But the expert statements still require things from their users. They require the court to make the decision what the laboratory result means (even though the court does not necessarily seem to perceive that requirement), and to make that decision possible, the users must concern themselves with some of its inner workings, most prominently the uncertainty inherent in forensic evidence. But the users really aren’t (meant to be) given the interpretive flexibility a boundary object—another STS knowledge object—offers. So, I call the statements semi-transparent boxes, because, like black boxes, they are meant as a neat, stable, and usable package that can easily be handed to a user, but, unlike black boxes, they don’t hide away everything about how the package has been made, only some of it.

Reasonably, producing such a semi-transparent box shouldn’t require very different conditions from producing a black box or any other knowledge object. What does, however, require a lot of work is to actually keep it semi-transparent: the recipients of the semi-transparent box need to know how to see through its walls properly. When the court doesn’t realize that they are required to look at the uncertainty packaged into an expert statement and make a decision about the laboratory result, they treat what is constructed as a semi-transparent box as if it were a black box. But that’s not what the forensic scientists intended; in fact, when the semi-transparent box is treated like a black box, it isn’t stable: the court doesn’t see the meanings the box is meant to carry.

So—and this something I am working on now—I think that STS’s focus on objects such as immutable mobiles, black boxes, and boundary objects when theorizing about the movement of knowledge is a bit too narrow. I think there need to be structures in place for the reception of knowledge objects, for example, teaching recipients how to read expert statements. Or, as is the case in the criminal justice system, translation work that puts readings back on track. I think it could be really fruitful to widen the analytical focus and look at the structures that are (or are not) put in place around the movement of knowledge.

IG: So much of the work of moving forensic evidence from crime scene to court is about what you aptly call translation work. I was wondering if you could say a little about the differences between how you understand the translation work people are doing and the ways your fieldwork interlocutors understood this work.    

CK: For me, thinking about epistemic cultures and languages has been a very fruitful way to try to understand how forensic evidence moves (or is moved) through the criminal justice system, exactly because I felt that STS’s different knowledge objects didn’t really give me the analytic leverage I was looking for.

But I don’t think that members of the criminal justice system see themselves as belonging to different cultures with different epistemologies and languages. Of course they are aware—and occasionally frustrated—that there can be communication difficulties and frictions, but when they discuss them (at least with me), they seem to put them primarily in terms of others not understanding what is evident to them. For example, crime scene technicians can say that forensic scientists don’t go to crime scenes, so they don’t understand what they are like and, in consequence, they don’t understand why crime scene technicians cannot always deliver traces or documentation in exactly the way the laboratory demands. Or, forensic scientists can talk about how probabilistic evidence is difficult for prosecutors and judges to understand and thus needs to be explained to them. It’s not that they’re not smart, forensic scientists say, but they’re not good at maths—if they were, they’d be scientists—and thus they don’t like numbers.

Likewise, much of what I call translation work would be called “explaining” by my interlocutors. So, my impression is that, generally speaking, members of the criminal justice system seem to see disseminating information as the way toward resolving friction, and they see information as not rooted in contexts or epistemic cultures. In other words, I think they conceptualize friction as arising because of lack of information —not because of different world views. Thus, they don’t see the need for translations.

I hope, though, that my notion of translation work might be of use to them. Not because I want to claim that I have a somehow better understanding of their work than they do—I don’t—but because having seen the different parts of the criminal justice system instead of being very familiar with only one has given me a different perspective. I hope that by giving my interlocutors a glimpse of each other’s practices, epistemologies, and languages as well as suggesting a vocabulary with which to talk about their differences, I give them a set of tools for perceiving and resolving friction in a different way. If they want to, that is.


Simon Cole, 2010 “Acculturating Forensic Science: What Is ‘Scientific Culture,’ and How Can Forensic Science Adopt It?” Fordham Urban Law Journal 38(2): 435-472.

Simon Cole, 2013 “Forensic Culture as Epistemic Culture: The Sociology of Forensic Science.” Studies in History and Philosophy of Biological and Biomedical Sciences 44: 36-46.

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