Imrahil said:
Since when is fornication punishable by death?
Deuteronomy 22:14, 20-21
"I took this woman, and when I came to her I found she was not a virgin..." But if the thing is true, and evidences of virginity are not found for the young woman, then they shall bring out the young woman to the door of her father's house, and the men of her city shall stone her to death with stones, because she has done a disgraceful thing in Israel, to play the harlot in her father's house. So you shall put away the evil from among you.
Deuteronomy 22:23-24
"If a young woman who is a virgin is betrothed to a husband, and a man finds her in the city and lies with her, then you shall bring them both out to the gate of that city, and you shall stone them to death with stones, the young woman because she did not cry out in the city, and the man because he humbled his neighbor's wife; so you shall put away the evil from among you."
(This last one might arguably be considered adultery, but could (and has) been used as a legal point against fornication, the first is brought up in the NT as kind of an obtuse reference by Jesus when he referred to allowing divorce in cases of fornication.)