Responsa for Yevamot 60:11
אמר ליה אביי אי הכי בקדושין נמי נימא אשה זו בחזקת היתר ליבם עומדת ומספק אתה בא לאוסרה אל תאסרנה מספק
THE BETROTHAL OR DIVORCE<span class="x" onmousemove="('comment',' On the part of the deceased childless brother. ');"><sup>24</sup></span> WAS IN DOUBT, BEHOLD, THESE RIVALS MUST PERFORM THE HALIZAH<span class="x" onmousemove="('comment',' Since it is possible that the betrothal was, or that the divorce was not valid, and they are consequently the rivals of a forbidden relative. ');"><sup>25</sup></span> BUT MAY NOT BE TAKEN IN LEVIRATE MARRIAGE.<span class="x" onmousemove="('comment',' It being possible that the betrothal was not, or that the divorce was valid and they are, therefore, not rivals of a forbidden relative. ');"><sup>26</sup></span>
Teshuvot Maharam
A. Had the witnesses seen the ring fall into Leah's lap, she would need a divorce in spite of her claim that she never intended to become A's wife and that she was joking when she asked him to betroth her. For we would, then, be concerned only with facts and not with her thoughts and unexpressed intentions. But, since the witnesses did not see the ring fall into Leah's lap, and the yard where the incident took place did not belong to Leah, she needs no divorce, for no betrothal took place. R. Meir adds: If my teachers agree with my decision, all will be well. But if they do not agree I shall subscribe to whatever they decide to do. However, I should prefer not to be strict in this matter and not to require Leah to obtain a divorce, lest A become rebellious and refuse to divorce her, and lest he travel to a distant land and thus render it impossible for the unfortunate woman ever to marry again.
This Responsum is addressed to: "My teacher Rabbi Haim and his court."
SOURCES: Pr. 993: Mord. Git. 451; ibid. Kid. 548: Tesh. Maim. to Nashim. 1.