Aaron Hernandez' fiancee didn't lie to investigators in the murder case against her man ... because she was in the dark just like everyone else, according to her lawyers.
Shayanna Jenkins appeared in a Massachusetts courtroom just a short time ago ... to face arraignment on one count of perjury for allegedly lying about dumping a box somewhere that allegedly contained the murder weapon. She claimed she didn't remember where she tossed it.
Her attorneys told the judge Shayanna didn't lie about anything ... because Aaron had a "don't ask, don't tell" relationship with her.
In fact, her lawyers say Shayanna actually provided information to cops ... that the murder victim -- Odin Lloyd -- provided weed to Hernandez.
Shayanna pleaded not guilty and was released on personal recognizance.