Answer:
To show reference, and similarities in cases. Other cases may even be relevant to current cases. They may also, do so if they think the unsolved case could have something to do with the current suspect of a case.
Common sense - a book to persuade people to rally colonists around the idea of independence or to fight
Http://openstudy.com/updates/53b42519e4b09f140ca4ce20
I hope this helps