How can the Torah consider "Im Lo'Shachav Ish osach ... Hinaki", which implies guilt, a Shevu'ah?
Rashi (From Sanhedrin 32b): The Shevu'ah lies in the inference - 'Im Shachav osach, Chinaki!' ('If he did lie with you, you will be strangled!') In capital cases, we begin with acquittal.
Why does the Pasuk add the phrase "Im Lo Shachav Ish osach, ve Im Lo Satis Tum'ah Tachas Ishech"?
Ramban #1: to clarify that he (the Kohen) is referring to another an, other than her husband, who is also a man, and with whom she was entitled to have been intimate.
Ramban #2: Assuming that the word "Ish" is missing a 'Hey', the Pasuk means that she did not lie with the man in question, nor with any other man. 1
Seforno: The Pasuk means that she did not commit adultery on this occasion or on any previous occasion. 2
What are the connotations of "Hinaki"?
Rashi, Targum Onkelos and Targum Yonasan: It means that the Sotah will be proven innocent.
Seforno: Bearing in mind the Pasuk the Pasuk in Shemos, 20:7, "Ki Lo Yinakeh Hashem Es asher Yisa Es Shemo la'Shav", implicating anyone who swears - even truthful - unnecessarily, the Kohen releases her from the sin of Shevu'as Shav here, even though she brought the need to swear upon herself by her actions.
QUESTIONS ON RASHI
Rashi writes that he begins with "Im Lo Shachav...", for in capital cases, we begin with acquittal (Sanhedrin 32b). In any case, the first side of a Tenai is Hen (Gitin 75b), i.e. fulfillment of the Tenai)!
Moshav Zekeinim: Sanhedrin 32b holds like the opinion that does not require a double Tenai, or 'Hen' first.