You are incorrect. There is no internal forum that as you suggest determines anything.
The Vatican has made it very clear that these matters can be resolved through the “internal forum” or ones on conscience.
There are times when the annulment procedure itself is sinful on the part of the person who applies. What would you think of a person who petitioned for annulment KNOWING that a relative of the ex had just had a stroke or was in poor health, AND that Ex still INSISTED on sending a questionnaire to that sick former in-law, and did not bother to tell the Tribunal of this little detail?
Also, many deal with mental illness, alcoholism, drug abuse, verbal and physical abuse with relatives and former in-laws who might not take well to any questionnaires received in the mail.
These are the situations which DEMAND some internal examination of conscience, to determine if the Catholic involved really NEEDS the opinion of 3rd parties, as to the validity of a marriage.
I suggest you read the book “With Open Arms” by John Hosie.
http://www.amazon.com/With-Open-Arms-Catholics-Remarriage/dp/089243810X
There are many other valid church documents which support what I am telling you.
“Thou shalt not bear false witness against they neighbor” is a Commandment, and many Catholics are guilty of this sin, when they judge those who have divorced and remarried.