Aaron Hernandez Fiancee -- Perjury Charge Dropped ... After Helping Convict NFL Star

The judge in the Aaron Hernandez murder case ... the first one ... has officially thrown out the perjury charge against Aaron's fiancee Shayanna Jenkins after she provided testimony that led to the conviction of the ex-NFL star.

Jenkins had struck a deal with prosecutors before she got on the stand -- she would talk and in exchange they would toss out a previous perjury charge.

The perjury charge stemmed from comments Jenkins made to the grand jury in 2013 regarding a gun in her home ... that may have been the weapon used to murder Odin Lloyd. If convicted, she faced up to 20 years behind bars.

Prosecutors say Jenkins' testimony at the trial -- that she helped Aaron dispose of a mystery box after Odin's death -- helped them win the case.

The operating theory is that the box contained the murder weapon.