A key resource is the Home Office policing policy which includes the PACE codes and statistics.
For resources about Stephen Lawrence or policing and ethnicity, search the Library Catalogue for police racism or police ethnic minorities
Provides access to research briefings produced by the House of Commons Library, the House of Lords Library and the Parliamentary Office of Science and Technology (POST). You can filter the research briefings by date, type, or one of 350 topics.
There are lots of resources in this area but do be aware that many provide 'alternative' views - make sure you evaluate any of the resources you use for their academic content, authority and reliability.
Modern Slavery:
Government Collection of resources on Modern Slavery
Child Trafficking:
NSPCC - resources on child trafficking and modern slavery
Every Child Protected against Trafficking - reports and guidance
County Lines: