A pilot randomised controlled trial of a critical time intervention for people leaving prison: findings from an integrated process evaluation

Williams, Adam Dale Newman, Jacob, Nina, Moriarty, Yvonne ORCID: https://orcid.org/0000-0002-7608-4699, Madoc-Jones, Iolo, Fitzpatrick, Suzanne, Mackie, Peter ORCID: https://orcid.org/0000-0003-1494-0864, Thomas, Ian ORCID: https://orcid.org/0000-0001-9808-0202, Grozeva, Detelina ORCID: https://orcid.org/0000-0003-3239-8415, Lloyd, Barry ORCID: https://orcid.org/0000-0003-4763-1726, Deidda, Manuela, Achiaw, Samuel Owusu, Lewis, Kelly, Cannings-John, Rebecca ORCID: https://orcid.org/0000-0001-5235-6517, Katikireddi, Srinivasa Vittal, White, James ORCID: https://orcid.org/0000-0001-8371-8453 and Lewsey, Jim 2025. A pilot randomised controlled trial of a critical time intervention for people leaving prison: findings from an integrated process evaluation. BMJ Open 15 (12) , e097761. 10.1136/bmjopen-2024-097761

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Abstract

Background: We conducted a pilot randomised controlled trial (the PHaCT study), including a process evaluation to assess the acceptability of a housing-led Critical Time Intervention (CTI) for prison leavers and the use of a trial design. This paper presents the process evaluation findings. Objective: To explore the acceptability of both the intervention and the trial design to participants and those delivering the intervention, and to assess whether the intervention was delivered with fidelity. Design: A process evaluation following Medical Research Council guidelines. Data collection included semi-structured interviews with participants and CTI caseworkers and observations of intervention delivery. A thematic analysis of interviews and observations was conducted to understand the intervention’s implementation and contextual factors as well as the trial process acceptability. Setting: Participants for the pilot trial were recruited from three prisons in England and Wales where the intervention was being delivered. Participants: While 28 out of 34 trial participants consented to interviews, only one was completed. Seven caseworkers were interviewed. Intervention: A housing-led CTI to support people leaving prison at risk of homelessness, involving phased, time-limited support from caseworkers, starting prerelease and continuing postrelease, to help secure stable housing and build independence, without directly providing housing. Results: The intervention’s acceptability was primarily reflected through the positive feedback and success stories shared by CTI caseworkers, as well as observational data indicating high acceptance among service users. The trial design’s acceptability was challenged by concerns about randomisation and equipoise, with staff viewing randomisation as unethical due to limited support for vulnerable populations. The fidelity to the CTI intervention housing-led approach was adhered to as best as possible; stable housing was prioritised for service users before addressing other needs. Despite these efforts, both sites encountered significant challenges due to limited housing availability and complex systems for securing social housing, particularly for single men leaving prison. Conclusions: This wider study faced significant challenges which impacted the process evaluation. Despite these issues, the evaluation provides important insights into the challenges of conducting trials on interventions for people leaving prison. The challenges experienced should inform future study designs with similar populations and in similar settings. Trial registration number: ISRCTN46969988.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Schools > Medicine Schools > Geography and Planning (GEOPL) Schools > Social Sciences (Includes Criminology and Education) Research Institutes & Centres > Centre for Trials Research (CNTRR)
Additional Information:	License information from Publisher: LICENSE 1: URL: https://creativecommons.org/licenses/by/4.0/, Start Date: 2025-12-17, Type: open-access
Publisher:	BMJ Publishing Group
ISSN:	2044-6055
Date of First Compliant Deposit:	6 January 2026
Date of Acceptance:	28 October 2025
Last Modified:	06 Jan 2026 11:45
URI:	https://orca.cardiff.ac.uk/id/eprint/183581

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