Yevamos 12:4-5

Yevamos 12:4

If a woman performed chalitzah on a man with congenital deafness, or if a woman with congenital deafness performed chalitzah, or if a woman performed chalitzah on a minor, in all of these cases the chalitzah is invalid. If a minor girl performed chalitzah, she must do it again when she reaches the age of majority. If she does not perform chalitzah again after coming of age, the chalitzah she performed as a minor is invalid.

Yevamos 12:5

If a woman performed chalitzah in front of two judges (rather than three), or if she performed it in front of three judges but one of them was found to be a relative or was disqualified for some other reason, the chalitzah is invalid. Rabbi Shimon and Rabbi Yochanan HaSandlar say that it is valid. It once happened that chalitzah was performed when the man and woman were alone in prison. (The Talmud on Yevamos 105b explains that there were witnesses.) The case was brought to Rabbi Akiva, who ruled that the chalitzah was valid.