This report examines the law and prosecution practice concerning secondary liability, often referred to as ‘Joint Enterprise’. Focusing on homicide cases, it highlights the risks posed by the current ambiguous law and makes a case for creating a safer framework for prosecution. It finds that Joint Enterprise laws are vague and wide in scope, causing systemic injustice, including over-criminalisation, over-punishment, discriminatory outcomes, and convictions where there is no compelling evidence of intent and a defendant’s physical contribution is minimal. The report is part of the Young Adult Safety project at the Centre for Crime and Justice Studies. This project aims to strengthen advocacy about the key aspects of serious violence that affect young adults.