The charges stemmed from a June 2011 trip by the woman to visit the suspect and his brother.
After a spell of heavy drinking together, the trio retired to a cabin at which point the woman passed out, the local Västerbotten-Kuriren (VK) newspaper reported.
Sometime in the middle of the night, however, the woman was awakened to find the 28-year-old having sex with her without her consent.
As prosecutors deemed the woman to be in a helpless state at the time, rape charges were filed against the man.
But the 28-year-old claimed he was innocent, arguing he too was asleep when he carried out the alleged rape and thus could not be held culpable for the act.
“I was awakened by her pushing me away and asking, ‘Are you awake?’,” the man had said during police questioning, according to the Aftonbladet newspaper.
The 28-year-old explained that he suffers from somnambulism and sexsomnia, an affliction whereby sufferers perform sexual acts while still asleep.
The Lycksele District Court in northern Sweden agreed with the man’s defence, ruling on Monday that the 28-year-old could very well have been sleeping when he started to have sex with the woman and thus acquitted him of all charges.
Prosecutor Lotta Sundström told VK that the court was split in its ruling, however.
“That means I’m probably going to appeal,” she told the paper.
Swedish sleep expert Jerker Hetta also expressed doubts about the 28-year-old’s claims that he had sex with the woman while in his sleep.
“In this case, I don’t think it’s been shown that he was in a somnambulistic state,” he told VK.