This report aims to set out a preliminary understanding of what is and is not known about how children and young people's experiences of systems of support impact on their involvement in serious violence, based on a review of a sample of evidence from the Systems Evidence and Gap Map (EGM), an interactive tool published by the Department for Education (DfE) and Youth Endowment Fund (YEF), and interviews with experts. This report also highlight challenges to implementing approaches which may reduce involvement in violence. This evidence can be used by policymakers to design systems which maximise the protective factors (e.g. positive relationships) and guard against the risks (e.g. stigmatisation). Potential gaps in the evidence base are identified and drawn together under key questions and considerations for future research. This enables researchers and policymakers to understand the limitations of the evidence base for policy making, as well as avenues for future research which are likely to be useful. [This paper was produced with Open Innovation Team and Youth Endowment Fund (YEF).]