Analysing gang-related music linked to serious violence

The aim is to ensure that expert witness statements are completed to the required standard and that the correct terminology is used for gang association drill lyrics linked to serious violence.

The intended outcomes are to:

• improve officers’ knowledge of gang association drill lyrics
• improve the force’s response to address community concerns around the incorrect use of drill lyrics
• reduce the number of evidential case progression outcomes being based on untestable intelligence

In 2021, the Metropolitan Police Service (MPS) Serious Crime Review Group (SCRG) conducted a review into the quality of gang association drill lyrics evidence linked to serious violence, which is often presented in the form of expert‑witness statements. The review revealed that there were issues at court with how the evidence had been delivered and the choice of wording. Additionally, the review found problems with how officers are tasked and how they communicate with the investigation team when collating evidence. Public and community concerns were raised around officers acting as expert witnesses, with campaign groups seeking to ban the practice. In response, the force launched an initiative to professionalise and streamline the use of place names, nicknames and evolving slang linked to serious violence in expert witness statements.

Training

The team have developed a bespoke training course, which is delivered to officers who have experience in providing expertise in gangs and lyrical content. This involved a consultation and training from leading external academics. In preparation for the course, delegates are required to complete a pre‑read of guidance documents and supporting academic literature, prior to the one‑week in‑person training. The course content focuses on how to act as an expert witness in court. Throughout the training, the delegates are tested on their knowledge and ability through mock trials. 

Roles and teams

There is one detective sergeant (DS) who is responsible for the drugs expert witness cohort. The role of the DS is to assess and review each request of expert evidence and be a strategy advisor to the investigation teams. The DS will assign out suitable requests and track the tasking of expert witnesses. They are also responsible for quality‑assuring reports and managing the standards of the cohort of expert witnesses.

Under the supervision of the DS, a cohort of officers complete expert witness reports alongside their primary role; all reports are currently completed in overtime hours. Once finished, the reports are sent to the investigation teams and a central file is maintained to collate the submissions.

Central tasking form

A central tasking form has been created to ensure all requests for expert witness reports are recorded. As of February 2026, the form is mandatory and all material intended to be used as evidence must be submitted to the team. The evidence is then assessed by the team. 

How the material is assessed 

The MPS applies a serious crime threshold and limits the use of gang or music based evidence to cases where it is necessary and proportionate. Categories include where:

• context is essential: drill and rap music are performative genres and not inherently autobiographical
• relevance must be communicated: material must address a live evidential issue such as motive, presence or involvement
• corroboration matters: isolated references are rarely probative alone
• there is awareness of bias: commentary based on music, appearance, geography or social media need to be grounded and not based in inherent bias.
• time is relevant: material is required to fall within a meaningful timeframe for the alleged offence

Any officer using the material that falls into one of the categories is required to put a request into the team. The team can produce expert reports, navigate the nuances, advise on potential defence challenges and review defence expert witness reports.

During the review process, some material are assessed as not suitable to be supported and are rejected. This prevents poorly evidenced gang or lyrical evidence from becoming a distraction from the relevant principal evidence.

Funding and senior management approval 

Given that all reports are produced in overtime hours, a dedicated service code has been established, resulting in an expenditure of approximately £33,000 in the 2024/25 financial year. Development and implementation was approved at commander level.
 

An evaluation is ongoing and is being led by the MPS. It is examining 18 months of data relating to requests for gang‑evidence assessments, slang and drill music translations intended to be used as evidence in court. The data is being reviewed by an analyst to identify any potential age or racial disparities. The evaluation is also assessing how many requests have been processed and how many have been rejected.

A six‑month data‑capture exercise began in February 2026, which will provide the MPS with an improved data picture.

Feedback from the investigations teams indicates that the initiative has been successful in improving the quality and admissibility of slang and music-based evidence. There have been a number of high-profile successes in using relevant evidential drill music to support prosecutions.

While some material is rejected, this has been an important safeguard against possible wrongful conviction prosecution.

A number of new pieces of case law have been created between 2021 and 2025 which have supported the work of the team.

• It is important to have officers with local knowledge and the appropriate skill set to assist with the collation of evidential material.
• A key challenge has been developing a training package, which required external support from academics and independent experts. Although many were willing to contribute to the design and delivery of the training, funding remained a persistent issue.
• The topics being discussed need to be managed with cultural sensitivity. When presenting the initiative to senior officers, it was essential to ensure they understood and supported the project.