אבן העזר מ״דEven HaEzer 44

Se’if 1א׳

חֵרֵשׁ וְחֵרֶשֶׁת אֵינָם בְּנֵי קִדּוּשִׁין מִן הַתּוֹרָה, בֵּין נָשְׂאוּ כַּיּוֹצֵא בָּהֶן בֵּין חֵרֵשׁ שֶׁנָּשָׂא פִּקַּחַת בֵּין חֵרֶשֶׁת שֶׁנִּשֵּׂאת לְפִקֵּחַ; אֲבָל חֲכָמִים תִּקְּנוּ לָהֶם נִשּׂוּאִין. לְפִיכָךְ, אִם בָּא פִּקֵּחַ וְקִדֵּשׁ אֵשֶׁת חֵרֵשׁ הַפִּקַּחַת, הֲרֵי זוֹ מְקֻדֶּשֶׁת לַשֵּׁנִי קִדּוּשִׁין גְּמוּרִים, וְנוֹתֵן גֵּט וְהִיא מֻתֶּרֶת לְבַעֲלָהּ הַחֵרֵשׁ:

A deaf male or female is not legally capable of marriage by Biblical law, whether they married another deaf person, or a deaf man who married a cognitively normal (lit. clever) woman, or a deaf woman who married a cognitively normal man. But our sages decreed for them marriage. Therefore, if a normal person betrothes the normal wife of a deaf man, she is fully betrothed to the second (i.e. normal) man, and he gives a get, and she is permitted to her deaf husband.

Se’if 2ב׳

שׁוֹטֶה וְשׁוֹטִית אֵין לָהֶם קִדּוּשִׁין לֹא מִדִּבְרֵי תּוֹרָה וְלֹא מִדִּבְרֵי סוֹפְרִים, לֹא שְׁנָא עִם כַּיּוֹצֵא בָּהֶם לֹא שְׁנָא עִם פִּקְחִים. הַגָּה: וְדַוְקָא שׁוֹטֶה גָּמוּר; אֲבָל אִם דַּעְתּוֹ צְלוּלָה, אַף עַל פִּי שֶׁהִיא דַּלָּה וּקְלוּשָׁה הַרְבֵּה (ר"י בְּשֵׁם הָרַמָ"ה), וְכֵן עִתִּים שׁוֹטֶה וְעִתִּים צָלוּל, וְלֹא יָדַעְנוּ הָעֵת שֶׁהוּא עוֹמֵד בְּדַעְתּוֹ, חוֹשְׁשִׁין לְקִדּוּשִׁין (גַּם זֶה שָׁם):

Mentally incompetent men and women cannot become betrothed, neither at a Torah level nor a rabbinical level, whether with another person like them or a competent person. Rem"a: This only applies to a genuinely incompetent person, but if his thoughts are rational, even if he is extremely unintelligent, or is he has periods of incompetence and periods of rationality, and we cannot determine the periods during which he can think, we must be concerned for his betrothal.

Se’if 3ג׳

שִׁכּוֹר שֶׁקִּדֵּשׁ, קִדּוּשָׁיו קִדּוּשִׁין אֲפִלּוּ נִשְׁתַּכֵּר הַרְבֵּה; וְאִם הִגִּיעַ לְשִׁכְרוּתוֹ שֶׁל לוֹט, אֵין קִדּוּשָׁיו קִדּוּשִׁין. וּמִתְיַשְּׁבִין בְּדָבָר זֶה:

A drunk person who betrothed, his betrothal is valid even if he was very drunk. But if he reached the drunkenness of Lot (who had no recall of incest with his daughters), his betrothal is invalid. They need to carefully investigate this matter (i.e. to assess the degree of drunkenness very carefully).