The work performed for the InterPsy project consists of the following:
1. Data collection
The primary sources collected and analyzed for the project consist primarily of interrogation manuals, articles about interrogation in specialized journals, scientific publications on criminal interrogations, and criminal case records including interrogation records. Selections from various archives and journals were made, focusing on material from France, Germany and the Netherlands between 1880 and 1940 in libraries and archives in Paris, Berlin, Utrecht and Haarlem. The collected material was made available in a public repository (Yoda), as far as it was no longer under copyright, subject to privacy legislation, or already accessible in a public database.
2. Knowledge circulation & epistemic hierarchies
To study knowledge circulation and epistemic hierarchies, the project has primarily focused on the debates surrounding the phenomenon called ‘Tatbestandsdiagnostik’, a technique based primarily on word association to determine whether a suspect was guilty of a given crime, developed in the German-speaking world in the early twentieth century.
This has resulted in several presentations at conferences and the following article: Elwin Hofman, “Experimental Interrogations: Tatbestandsdiagnostik, Objectivity and the Impact of Experimental Psychology on Early-Twentieth-Century Criminal Justice,” NTM Journal of the History of Science, Technology and Medicine 33:4 (2025): 427-455.
The main finding of this part of the research is that the insistence of proponents of Tatbestandsdiagnostik on the method’s objectivity, its ambiguous relationship with psychoanalysis, and the possibility of demonstrating it to students and colleagues facilitated both its rapid rise and its demise.
The question of knowledge circulation and epistemic hierarchies will also be expanded upon in a chapter in a monograph on the history of criminal interrogation (in progress).
3. Interrogation practices
To study the practice of criminal interrogation in relation to scientific knowledge, the project has focused on the experience of criminal interrogation, that is to say, its sensorial and emotional effects on both interrogators and suspects.
Attending to sensory experiences shows that, contrary to what is often assumed, early-twentieth-century interrogation was not just a remnant of older investigative techniques. The interrogation changed profoundly, for instance by allowing suspects to sit down, by permitting smoking in interrogation rooms, and by the advent of clattering typewriters and stenotype machines. This led to new interactions, new ways of speaking and recording, and new strategies for interrogators and suspects. Under the influence of the professionalization, scientificization, and modernization of police investigations, the interrogation changed in ways that were often not made explicit but were certainly felt by those involved.
This has resulted in several conference papers and a book chapter: Elwin Hofman, “Sensing Modernity: The Experience of Police Interrogation in Interwar Berlin,” New Histories of Crime: Topics, Methods, Perspectives ed. Maurice Cottier and Joachim Eibach (Munich: UVK, 2026) in press. The topic will also be put in a comparative perspective in a chapter in a monograph on the history of criminal interrogation (in progress).
4. Workshop
On 13 September 2024, an interdisciplinary workshop was organized in Utrecht, The Netherlands, as part of the InterPsy project. The theme of the conference was ‘Criminal Interrogation: Past & Present’. A group of ca. 30 scholars discussed precirculated papers clustered around the themes of ‘interrogation records’, ‘gender’, ‘science, knowledge & technology’ and ‘human rights’. The workshop was successful in establishing conversations between scholars from different disciplines working about criminal interrogations and showcased the variety of ongoing research on the topic.
5. Communication and outreach
Apart from the scholarly publications, conference papers and workshop mentioned above, results from the project were communicated to a wider audience via, among other, presentations at the Betweter Science Festival (Utrecht, 26 September 2025) and Studium Generale (Utrecht, 17 February 2025), as well as an interview on Dutch public radio (De Nacht van NTR Wetenschap, NPO Radio 1, 4 September 2025). As part of the project, the researcher also conducted a secondment at NTR Geschiedenis, a Dutch public broadcaster, to develop a scenario for a documentary highlight the impact of psychology on criminal interrogations.
