Kiddushin 65: Previously Betrothed? Admitting a Transgression and the Need for Witnesses

The rabbis are still discussing the details of kiddushin when that kiddushin is in fact not permitted.  Today's daf introduces a new Mishna where two people disagree about a previous betrothal.  The man says that he and a woman are betrothed, but she says that they are not betrothed.  A woman says that they are betrothed but the man disagrees.  And a man says that he is betrothed to a woman but she says that he is betrothed to her daughter.  

In each of these cases, the Mishna states who is forbidden to whom.  When a person says that s/he is betrothed to another person, s/he disqualifies that person's family members from having relations with him/herself, as well.  However, when a person says that s/he is not betrothed, family members are permitted.

Interestingly, in these cases a woman's statement is taken as fact.  This is significant, particularly when we are talking about potentially forbidden relations that could result in mamzerim.  Usually, such a risk is dealt with stringently.  Why would the rabbis value a woman's opinion on whether or not she was previously betrothed?

The Gemara wonders whether there were any witnesses to the betrothal, whether the betrothal was performed overseas, whether there were multiple witnesses, and whether or not those witnesses saw merely seclusion or an act of sexual intercourse.  Beit Shammai say that witnesses of simple seclusion are valid witnesses, while Beit Hillel say that witnesses must have seen an act of intercourse.  

While this might seem to suggest that Beit Hillel are more stringent, in practice it would mean that Beit Hillel were more lenient.  In a court, judges would value the testimony of witnesses who saw an act of intercourse.  There would be few of these witnesses, and thus few cases of people insisting that they were betrothed when they were simply wishing to benefit from that status in some way (including intercourse with the woman in question).
Then again, this might disadvantage a woman who has in fact been betrothed but whose husband does not wish to support her or pay her ketubah.

Another example involves a woman, two men, and a bundle that arrive from overseas.  Each man says that the woman is their wife and the other man is their slave; that the bundle belongs to them.  The woman says that both men are her slaves and that the bundle belongs to her.  We learn that each is granted bills of divorce from the other (s in the woman's case) because of the uncertainty regarding betrothal.  Further, the woman is given her ketubah payment from the bundle.

After discussing whether or not there might have been witnesses to the betrothal of one of the couples above, the rabbis turn to the question of admitting one's guilt.  We are told that "witnesses are created only for liars", and that witnesses should not be questioned at all if one admits to a transgression.  

It is interesting that the rabbis were satisfied with the credibility of a person who admitted to his/her own guilt.  What if a witness might testify otherwise?  Perhaps the person who admits his/her guilt has been coerced to do so.  Or perhaps s/he is not a reliable witness due to mental health issues, memory impairment, or other reasons.  I have a feeling that today's daf is not the end of this conversation about the credibility of one who admits guilt.