Research Papers / Paper on Euthanasia-How to argue it can be research paper & not just persuasive [5]

I need to do a 4500 word research paper on any topic. I want to do one on Euthanasia but my professor said it would be more of a persuasive rather than research paper. I can see it taking a persuasive tone, but don't see how it couldn't be a research paper with the Netherlands, Belgium legalizing it, as well as Oregon here in the US. I've been out of school awhile and was hoping for some help on how to argue this point and get it approved. Any input would be most appreciated. Thanks for your help!