If four morally corrupt men, slaves, or blind men testify to zina, there are two narrations regarding this. According to one, they are slanderers and are subject to the fixed penalty. According to the other, they are not subject to any fixed penalty, because the completion of the required number has a bearing on waiving the fixed penalty from the witnesses, even though their testimony is rejected.
If four men testify to zina, while trustworthy women testify that the woman is a virgin, neither the woman nor the witnesses is subject to the fixed penalty. Had their number been incomplete, the witnesses would have been subject to the fixed penalty. This is because the required number has been completed, and they are generally qualified to give testimony: according to Ahmad (may Allah have mercy on him), slaves and blind people are generally qualified to testify. As for moral corruption, determining it is a matter of independent legal reasoning; one judge may reject their testimony while another accepts it. Thus, it is not conclusive, whereas an insufficient number is conclusive.
According to the third narration, if the witnesses are blind, they are subject to the fixed penalty; but if they are slaves, or even one of them is a slave, they are not subject to it. This is because the falsity of blind witnesses is certain, since zina is established through direct observation, whereas it is not possible to be certain that slaves are lying. This narration was transmitted by Sindi ibn Abd Allah al-Jawhari.
If the legally admissible evidence consists of testimony that the accused confessed to zina, it is not permissible to suffice with two witnesses; no fewer than four are acceptable.
When the adulterer is stoned, no pit is dug for him during the stoning, whereas one is dug for the woman. If the adulterer flees while being stoned, the ruling is as follows: if he was sentenced on the basis of testimony, he is pursued and stoned until death; but if he was sentenced on the basis of his confession, he is not pursued.
When stoning has been established through testimony, the witnesses are not required to attend the stoning or to initiate it. Likewise, when it has been established through his confession, the imam is not required to attend the stoning or to initiate it. Abu Bakr mentioned this.
A pregnant woman is not subjected to the fixed penalty until she gives birth, nor after giving birth until someone can be found to nurse her child. If, in a zina case, the accused claims a plausible doubt—such as an invalid marriage, mistaking the woman for his wife, or being unaware that zina is prohibited while being a recent convert to Islam—the fixed penalty is waived on that basis, in accordance with the Sunnah.