Hopefully this is only a theoretical question. Can a geir perform hatafat dam berit on himself?
No. Since he is doing it, he is either definitely not yet a geir or it is a safeik whether he is yet a geir. Therefore, the hatafah does not work.
Regarding milah for a Jewish baby, the Shulchan Arukh (YD 264:1) says that the mohel has to be Jewish, but if he was not-Jewish the baby does not need a second milah. Some commentators understand that to mean that bedieved a non-Jew can be a mohel for a Jewish baby (See Taz there), but many others understand that it means that the milah was not good, and now there is nothing that can be done to make it better. It seems to me based on the Gemara (Avodah Zarah 27a) the latter reading is definitely the peshat.
That is for milah for a Jewish baby. For a geir, however, it is about making him Jewish, and the Shulchan Arukh YD 268:3 rules that we need a beit din of 3 men, and a kosher bein din would preclude non-Jews. However, following Tosafot (Yevamot 47a s.v. yeish lekha eidim), he rules that, bedieved, 3 are only needed for kabbalat mitzvot, and that 2 suffice for the rest, milah and tevilah. The commentators say that the 2 are really only needed as eidim, and that really one suffices. This might open the door to say that it doesn’t even require anyone to be Jewish as part of these stages. And, indeed, the Gemara talks about someone who says that they converted on their own, and the prime question is believability, not whether it was possible. All that being said, the assumption is that a milah performed by a non-Jew is not good for geirut.
Achiezer 3:27 deals with the case of milah for giyur done by a non-Jew. He states that it is not effective even if a rabbi is supervising (עומד על גביו). The reason that it might be acceptable in the case of Jewish baby is because you don’t need kavanah in that case, as that is what is normally done for a Jewish 8-day old boy, the act defines itself as being done for that purpose (סתמן לשמה קאי), which is not the case for a non-Jew whom we are trying to make Jewish. There you needed express intent, and it is assumed that a non-Jewish mohel cannot provide it. Two interesting points to consider:
- If the hatafah is only required lechumrah, such as for someone who has been living like a Jew, is it possible to say that based on his circumstances (if not halakhic demands) he is סתמן לשמה קאי?
- It is worth noting that the focus of the problem is not the personhood of the mohel. The fact that he is a non-Jew does not seems to be an issue, and the concern is only intent.
Here are the key lines from Achiezer 3:27,
אולם בדברי שאלתם חזיתי אשר הטפת ד”ב הי’ ע”י שני רופאים ערלים במעמד הראבינער, וא”כ הי’ הדבר, הדין הוא שצריך הטפת ד”ב מחדש ע”י רופא או מוהל ישראל, ואבאר הדבר: הנה בישראל שנמול ע”י הנכרי פסק המחבר בשו”ע יו”ד סי’ רס”ו דא”צ למול עוד, והרמ”א כתב דיש חולקין וצריך הטפת ד”ב, אבל לענין גירות פסק בסי’ רס”ח בנימול בגיותו שצריך להטיף ד”ב בלי שום חולק …
בישראל הנמול לכן אם המוהל הוא עכו”ם כשר דמילה בישראל סתמא לשמה קאי דעומד למול,…אבל בעכו”ם דהמילה היא לשם גירות /לקדשו/ וקדשו לשם ישראל ע”י מעשה המילה בזה לא אמרינן סתמא לשמה, ולכן צריך הטפת ד”ב, וכיון דהטפת ד”ב שהי’ בניד”ד הי’ ע”י רופאים נכרים אינה נחשב כלל לשם גירות.
According to some, while a Jew is needed to do milah, in this case, if the geir-to-be becomes a Jew at the moment of the hatafat dam berit, perhaps we would say that his status as a Jew and the validity of the act of milah that makes him a Jew all come at the same time (like גיטו וידו באין כאחת). This possibility assumes that he can become a Jew even though the tevilah (assuming there was an earlier one, like this is being done again מספק) came before. If you need the tevilah afterwards, then this act does not yet make him Jewish. (Some want to suggest, however, that once there is a tevilah, he retroactively has some Jewish status already at this moment).
For this fascinating possibility, see Minchat Chinuch 2:3
ונראה פשוט דגר שבא להתגייר אינו רשאי למול בעצמו כי אכתי עכו”ם הוא כ”ז שלא טבל. אך לשיטת הפוסקים בה’ גרים דטבילה ואחר כך מילה נמי מהני בגר אם טבל מקודם אפשר דרשאי למול בעצמו או אם עבר ומל א”צ להטד”ב אף שהוא עדיין עכו”ם מכל מקום מילתו וגירותו באים כאחד.