Cover: Classifying acts of violence

Classifying acts of violence

Understanding how acts of violence are classified by subject matter experts

Published Oct 27, 2021

by Sarah Grand-Clement, Diana Dascalu, Ruth Harris, Ben Baruch

Download Free Electronic Document

FormatFile SizeNotes
PDF file 0.8 MB

Use Adobe Acrobat Reader version 10 or higher for the best experience.

Research Questions

  1. How do subject matter experts (SMEs) classify different types of violent acts, and can distinctions be drawn between different types of SMEs?
  2. What drives the rationale behind the classification by SMEs and what can explain differences in classification (if any exist)?
  3. Based on RQs 1 and 2, what key findings and recommendations emerge for the Homeland Security Group?

Classifying acts of violence, particularly terrorism, is an ongoing challenge. There are risks to society as a whole if a specific act has been misclassified. For example, this can distort statistics and affect the understanding of, as well as the risks associated with, a phenomenon. In addition, misclassification can lead to the release of offenders who could still be of harm to others. In this context, RAND Europe was commissioned to undertake a study on how different acts of violence are classified by subject matter experts (SMEs).

The study was based on the inputs of 25 SMEs from a range of backgrounds (government/policy, practitioners, and academia/research) and fields (e.g. counter-terrorism, legal, policing, etc.). The SMEs first responded to a questionnaire to classify 12 case studies displaying acts of violence, then participated in a two-hour workshop, in which four of the case studies and their classification were discussed in more detail.

The findings demonstrate the ongoing difficulties in classifying acts of violence. Defining such acts is not done in isolation, but comprises many different facets of the crime, including the perpetrator's motivation, the significance of their online presence, any known or emerging mental health issues, and the classifier's own knowledge, experience, and possibly any resulting biases. The misclassification of complex crimes, especially those with probable or verified connections to terrorism, bring significant risks. Based on the findings, the study team offers several recommendations for policymakers.

Key Findings

Knowledge of the perpetrator's motivation is key in enabling classification

  • Lack of clarity around motivation could result in stakeholders implying a motive, which may involve biases.

Recognition of an ideology behind an act of violence can affect classification

  • Recognising an idea or movement as an ideology can enable prosecution under TACT 2000.

Social media and public perception can affect classification

  • SMEs cautioned against excessive reliance on social media in classifying acts of violence, and highlighted potential issues connected to classification and public perception.

Mental health issues can complicate classification

  • There was uncertainty as to how mental health affects the classification of acts of violence, as well as whether or not it should.

Defining an act as terrorism remains complex and, in some cases, unclear

  • SMEs noted that over-classification of violence as terrorism can, on the one hand, trivialise this type of act; on the other hand, it can have a wider societal impact.

Applications of hate crime can be unclear

  • The fact that gender is not included as a protected characteristic in the hate crime definition was not common knowledge. In addition, SMEs questioned whether the definition would apply to crimes towards the perpetrator's 'in-group'.

Small differences were identified between how different SMEs approached and perceived the case studies

  • Small differences were identified between how different SMEs approached and perceived the case studies


  • Ensure that stakeholders are aware of amendments in UK law and counter-terrorism measures.
  • Ensure that stakeholders are aware of new ideologies.
  • Clarify the role of mental health in violent acts.
  • Clarify which acts should be classified as hate crime.
  • Create a database to record offences, especially those with suspected terrorism connections.
  • Continue to facilitate communication and collaboration between stakeholders.
  • Improve public communication on acts that lead to a large amount of public interest
  • Conduct further research on how different SMEs classify acts of violence.

Research conducted by

This research was commissioned by the Homeland Security Group – Home Office and conducted by RAND Europe.

This report is part of the RAND research report series. RAND reports present research findings and objective analysis that address the challenges facing the public and private sectors. All RAND reports undergo rigorous peer review to ensure high standards for research quality and objectivity.

This document and trademark(s) contained herein are protected by law. This representation of RAND intellectual property is provided for noncommercial use only. Unauthorized posting of this publication online is prohibited; linking directly to this product page is encouraged. Permission is required from RAND to reproduce, or reuse in another form, any of its research documents for commercial purposes. For information on reprint and reuse permissions, please visit

RAND is a nonprofit institution that helps improve policy and decisionmaking through research and analysis. RAND's publications do not necessarily reflect the opinions of its research clients and sponsors.