You do not validate a null hypothesis, you only reject it. Burden of proof is never on the theoretician. That's why the only scientifically sound statement so far on ghosts is "maybe".
Not sure where you're coming from on this. Criminal law employs the scienttific method, where the accused is presumed innocent until proven guilty. Similarly, any scientific analysis of reported ghost encounters should presume the paranormal to be innocent of being the culprit until proven otherwise.