I wanted to go into the subject of ספק ספיקא in short. The wife of a kohen was found not to have been a virgin, so she is forbidden since the sex might have been after she was betrothed. Tosphot asks what about the status that she is assumed Ok חזקת כשרות until proven otherwise? Answer: the prior status of the body חזקת הגוף goes against that since it shows she remained a virgin until the last possible minute. That pushes the act to be during the time she was betrothed. R. Akiva Eigger asks but status of "now" [חזקת השתא] pushes that back in time. I.e. we assume the way things are now goes back in time until the farthest possible moment. He answers that status does not join with status of her being allowed to her husband since these two different kinds of status say different things.(החזקות לא מצטרפות)
Rav Shach asked that R Eigger himself say elsewhere that that point itself is subject to an argument between Rav and Shmuel. His answer requires showing his point from a lot of places, but the short of it is that status of now only can put a prior status in doubt if the prior status was already weak. But if it is strong, then the status of now does not count at all.
