The ReAct (Recovery, Activity) project is an ENFSI (European Network of Forensic Science Institutes) supported initiative comprising a large consortium of laboratories. Here, the results from more than 23 laboratories are presented. The primary purpose was to design experiments simulating typical casework circumstances; collect data and to implement Bayesian networks to assess the value (i.e., likelihood ratio) of DNA results given activity level propositions. Two different experimental designs were used to simulate a robbery, where a screwdriver was used to force a door or window. Propositions and case information were chosen following laboratory feedback listing typical casework circumstances (included in the paper). In a direct transfer experiment, the defendant owned and used the screwdriver, but he did not force the door/window in question. An unknown person used the defendant's stolen screwdriver. In an indirect transfer experiment, the defendant neither owned, saw, nor used the screwdriver, nor did they force the door or window. For the second experiment, given the defence view, the defendant never held the screwdriver. We envisaged the situation where an object manipulated by the defendant (or the defendant himself/herself) would be touched by the unknown offender who would then force the window. It was found for the direct transfer experiment that unless a single contributor profile aligning with the known person's of interest profile was retrieved, the results did not allow to discriminate between propositions. On the other hand, for the indirect transfer experiment, both single and major contributor profiles that aligned with the person of interest (POI) supported the proposition that the person used the tool rather than an unknown person who had touched an object, when indeed the former was true. There was considerable variation in median recoveries of DNA between laboratories (between 200pg-5ng) for a given experiment if quantities are taken into account. These differences affect the likelihood ratios given activity level propositions. More than 2700 samples were analysed in the course of this study. Two different Bayesian Networks are made available via an open source application written in Shiny R: Shiny_React(). For comparison, all datasets were analysed using a qualitative method categorised into absent, single, major or other given contributors. The importance of standardising methods is emphasised, alongside the necessity of developing new approaches to assign the probability of laboratory-dependent DNA recovery. Freely accessible open databases play a crucial role in supporting these efforts.

Biological Sciences Group Victoria Police Forensic Services Department 31 ForensicDrive Macleod Vic 3085 Australia

Bundeskriminalamt Wiesbaden Germany

Bundeskriminalamt Wiesbaden Germany; International Commission on Missing Persons The Hague The Netherlands

Cellmark Forensic Services 16 Blacklands Way Abingdon OX14 1DY UK

Comisaría General de Policía Científica DNA Laboratory Julián González Segador Madrid Spain

Department of Forensic Medicine Sect Forensic Genetics University of Copenhagen Denmark

Department of Forensic Sciences Oslo University Hospital Oslo Norway

Department of Forensic Sciences Oslo University Hospital Oslo Norway; Centre for Ecological and Evolutionary Synthesis University of Oslo Norway

Department of Forensic Sciences Oslo University Hospital Oslo Norway; Department of Clinical Medicine University of Oslo Oslo Norway

Eurofins Forensic Services 1 Dukes Green Avenue Feltham TW14 0LR UK

Eurofins Forensic Services Building 414 Birchwood Park WA3 4FW UK

Eurofins Forensic Services Sir Alec Jeffrey's Building Calder Park WF2 7UA UK

Forensic Genetics Service Laboratoire National de Santé 1 Rue Louis Rech L 3555 Dudelange Luxembourg

Forensic Science Centre Ivan Vučetić MoI Ilica 335 Zagreb Croatia

Forensic Science Institute Berlin Police Tempelhofer Damm 12 12101 Berlin Germany

Forensic Science Ireland Backweston Science Campus Stacumny Lane Celbridge Co Kildare W23 FT2X Ireland

Health Sciences Authority 11 Outram Road Singapore 169078 Singapore

Institute of Criminalistics Police of the Czech Republic Bartolomejska 12 Prague 1 11000 Czech Republic

Institute of Legal Medicine Medical University of Innsbruck Muellerstrasse 44 6020 Innsbruck Austria

Institute of Legal Medicine Medical University of Innsbruck Muellerstrasse 44 6020 Innsbruck Austria; Forensic Science Program The Pennsylvania State University PA 16801 USA

Landeskriminalamt Baden Württemberg Taubenheimstr 85 70372 Stuttgart Germany

Landeskriminalamt Rheinland Pfalz Valenciaplatz 1 7 D 55118 Mainz Germany

Metropolitan Police Service Forensic Services 109 Lambeth Road London SE1 7LP UK

National Bureau of Investigation Forensic Laboratory Tikkurilantie 30 01370 Vantaa Finland

National Forensic Centre Ministry of Interior Kneza Miloša 103 Belgrade Serbia

National Forensic Centre Swedish Police Authority Linköping SE 581 94 Sweden

Office of the Chief Forensic Scientist Victoria Police Forensic Services Department Macleod Australia; School of Agriculture Biomedicine and Environment La Trobe University Bundoora Australia

School of Criminal Justice and Fondation pour la formation continue universitaire lausannoise University of Lausanne Switzerland; Unit of Forensic Genetics University Center of Legal Medicine Lausanne Geneva Lausanne University Hospital and University of Lausanne Chemin de la Vulliette 4 Lausanne CH 1000 Switzerland

The laboratory of Forensic Genetics The Cyprus Institute of Neurology and Genetics Nicosia Cyprus

Zurich Institute of Forensic Medicine University of Zurich Winterthurerstrasse 190 52 8057 Zürich Switzerland

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