Further historical source material is held by the Library, including:
Police Gazette 1797-1900 is available on microfilm (Mic. 956), with accompanying guides. There is a searchable online index to the Police Gazette, and the Library has digital scanners for downloading page images.
Local historical material pertaining to Essex can be found in:
Calendar of Queen's Bench indictments ancient relating to Essex, 1558-1603 in the Public Record Office also on microfilm (Mic. 382)
Calendar of Essex assize files in the Public Record Office 1559-1714 (Mic. 350-381), now available online through the Essex Record Office
Open access digitised resources are increasingly available, such as:
Crime, Prisons and Punishment 1770-1935 from the National Archives (free to search, charge for download)
The Library has quite extensive archival collections that have been assembled over the years, and you can find out more about these on our Special Collections web pages.
The Special Collections guide also links you to information about collections elsewhere in the UK and overseas. National archives, national libraries, and portals such as Archives Hub (for the UK) are often good starting points for your research.