This mishnah lists young women whose violator is exempt from paying the special fine. There are two reasons for the exemption:
The young woman does not meet the definition of a virgin, and the fine applies only to a virgin.
The act itself is a transgression punishable by death, and since he is liable to the death penalty he does not pay a monetary fine, in keeping with the principle that he receives the more severe punishment.
Young women who are not presumed to be virgins:
The wording of the mishnah: "Eilu hen ha-ne'aros she-ein lahen kenas" - these are the young women for whom there is no fine: one who violates a convert, a captive, or a maidservant. The reference is to a captive who was redeemed, a convert who converted, and a maidservant who was freed, but where these transitions occurred when they were over the age of three. Since they held the status of a gentile, a captive, or a maidservant after the age of three, we suspect that they were already violated and are no longer virgins, and for that reason the fine does not apply.
Rabbi Yehudah disagrees regarding the captive: a young woman taken captive who was redeemed retains her sanctity, and we assume that she was not violated during her captivity, even though she is older, meaning over the age of three.
Young women whose violator is liable to the death penalty:
Here the mishnah lists young women with whom the act is a transgression punishable by death:
His daughter.
His daughter's daughter.
His son's daughter.
His wife's daughter.
His wife's son's daughter.
His wife's daughter's daughter.
In all of these there is no fine and no payment, because he is liable to the death penalty at the hands of the court.
The principle: whoever is liable to the death penalty does not pay money:
Anyone facing the death penalty does not pay the monetary obligation, as it says in the verse dealing with two men who were fighting and struck a pregnant woman, causing her to miscarry: "Ve-lo yihyeh ason anosh ye'anesh" - when no fatality occurred, meaning no death was caused, they must pay for the loss of the fetus. But had there been a fatality, and they were liable to the death penalty for the killing, they would not be subject to "anosh ye'anesh" and would not pay. From here we learn that whoever is liable to the death penalty, one who must pay with his life, does not pay a monetary penalty.