When citing psychological incapacity as a ground for annulment, the petitioner (or the one filing the petition for nullity alleging this as a ground) must not only present an expert witness like a psychologist or psychiatrist to testify on this ground but also show that the expert witness conducted a series of tests to justify his/her psychiatric or psychological evaluation.
Thus, the Supreme Court said:
“The expert opinion of a psychiatrist arrived at after a maximum of seven (7) hours of interview, and unsupported by separate psychological tests, cannot tie the hands of the trial court and prevent it from making its own factual finding on what happened in this case. The probative force of the testimony of an expert does not lie in a mere statement of his theory or opinion, but rather in the assistance that he can render to the courts in showing the facts that serve as a basis for his criterion and the reasons upon which the logic of his conclusion is founded.” (The case of Edward N. Lim vs. Maria Cheryl Sta Cruz-Lim, GR No. 176464, February 4, 2010)