- Do premarital sexual relations effect Kiddushin (betrothal/first step of Jewish marriage) if there is no intention of getting married?
- If so, is the physical act itself determinative of whether or not there is a kinyan (transaction effecting Kiddushin)? (Let's say they would instead be just hugging and kissing: would that effect a kinyan also?)
- Does the Yichud (seclusion) that the couple is having effect Nisuin? What if there are no kosher witnesses around?
Premarital sexual intercourse is not a kinyan unless it is done with the intention of being koneh. Not only that, but the man must say as much. Rambam Hil Ishus 3:5 (my own translation):
Now, the seclusion works because there are witnesses and because they know that his intention is for marriage. (See Maggid Mishna.) If there's no witnesses, there's no kiddushin.
As a side note, there is a separate prohibition against premarital sex. See Rambam Hil. Ishus 1:4.