economics combined with research on murder and evil

You could integrate economics, as in social disciplines, if you know how to turn things you can talk about everything from everything. BUT... in your situation, I really would not bother. If your research question is really asking whether all murderers are considered evils ? Bringing economy will be hard and not necessarily relevant. Your question is good, and you really don't need to look far if you just need it to be interdisciplinary. In my opinion: it mainly concerns sociology (how culture and environment can be held responsible for someone's acts) and psychology (in link with sociology, like how society and social phenomena change a mindset and cause someone to do a crime). On top of that, you can bring a philosophical conception of the subject if you want (go check Hannah Arendt's work about Eichmann). Her theories are accurate. Get informations about the concept "banality of evil" she developped. And finally, your project will automatically be linked to history and politics (you need it for examples). So I wouldn't bother bringing economy into it, when you have all those social disciplines who can bring you a lot more and really be relevant.