I found this article via Joanna Penn. Susan J Morris writes on character murder:
There are many things that can put a writer in the mood for murder… Writer’s block, corrupted files, getting notes back from their editor… But I think the most important thing [...] is to figure out why you want him dead so badly. Only once you understand your own motives can you begin [to] give him a funeral to remember. Here are a few of the most basic—and effective—reasons to kill a character.
She's right. For all the varieties of murder out there one of the most important aspects is:
[...] how do you make your audience care?
Read the article here: http://www.omnivoracious.com/2011/08/how-to-kill-a-character.html