Responsa for Yevamot 201:11
<big><strong>גמ׳</strong></big> ומאחר דאפילו שלשה הדיוטות דיינין למה לי הא קמ"ל דבעינן בשלשה שיודעים להקרות כעין דיינים תנינא להא דתנו רבנן מצות חליצה בשלשה שיודעין להקרות כעין דיינים רבי יהודה אומר בחמשה
GEMARA. Since even THREE LAYMEN [are sufficient],<span class="x" onmousemove="('comment',' To constitute a tribunal for halizah. ');"><sup>30</sup></span> what need is there for JUDGES? — It is this that we were taught: That three men are required, who are capable of dictating [the prescribed texts]<span class="x" onmousemove="('comment',' Deut. XXV, 7-9. ');"><sup>31</sup></span> like judges.<span class="x" onmousemove="('comment',' The appropriate texts in the original Hebrew are dictated by members of the court to the levir and his sister-in-law, respectively, who must repeat them precisely as they hear them. Cf. Sot. 32a. ');"><sup>32</sup></span> Thus we have learned here what the Rabbis taught: The commandment of <i>halizah</i> is performed in the presence of three men who are able to dictate [the prescribed texts]<span class="x" onmousemove="('comment',' Deut. XXV, 7-9. ');"><sup>31</sup></span>
Teshuvot Maharam
A. Bediabad, in this case, means after the rite was performed. Nevertheless, the aforementioned performance of the rite is invalid, for a different reason: the shoe used was sewed with flaxen thread and, therefore, was never fit for this purpose. Since, however, the levir performed an invalid rite of halitzah, neither he nor his brothers are now permitted to marry the widow. Halitzah by the same levir being the only manner of releasing her, he may be forced, by persuasion or by flagellation, to repeat the rite with the proper shoe. For now the Mitzvah revolved on him alone, and we are permitted to scourge a Jew until he perform the required Mitzvot.
This Responsum is addressed to Rabbi Menahem of Würzburg.
SOURCES: Am I, 93, 94.