You can identify books not available in Boatwright by using WorldCat. the books can usually borrwed through the interlibrary loan system.
I would suggest doing searches for articles with "Murder" or "Homicide" (or other crimes of interest) in the title.
To search for books in Boatwright, use the Library Catalog. When dealing with a topic that can be used in many fields it is best to add a second word that describes your area of interest. for example, "murder" and "history". To find books on fictional accounts of murder, look for books on "Detective and mystery stories > History and criticism." Or start with a keyword search and, when you have found one or two relevant books, examine their subjects headings to help guide further searching, Remember that books are generally on broad topics and that you are not searching the full text, only the titles, subject headings, and--if you're lucky--the table of contents. For narrower topics, search for journal articles in a journal database such as Academic Search Complete, or one of the others listed under the "Articles" tab.