Not hard but that is just one aspect of Crime Scene Investigations. I would first get a job as a CSI or a Lab Analyst (latents, DNA, Firearms). Once in one of these fields, and you are trained to proficiency. Then you can start taking classes and workshops etc in Blood Spatter. Getting a B.A. or B.S and taking or researching spatter will not lead to doing just that. It will open the doors for a career in a field I mentioned above.
As far as I know there are no Blood Spatter experts that do only that and are not a consultant. I.E work for a lab only. The experts all started somewhere in a CSI unit or Lab first.