Danny Surratt was sentenced to 18 years in prison on March 20th.
Jurors in the 9th Judicial District in Lovington, NM found Surratt guilty of first-degree criminal sexual penetration of a minor charges on February 15th.
Surratt, 62, was arrested on September 1, 2010 and accused of sexually assaulting both the 9-year-old girl and her 16-year-old sister.
Surratt was a Lea County Sheriff's deputy at the time the the alleged incident took place.
According to The Carlsbad Current-Argus, Surratt was arrested after the 9-year-old girl reported the incident.
New Mexico State Police also investigated the claim.
During the trial against Surratt, the 9-year-old victim reportedly testified that Surratt sexually assaulted her and told her not to say anything.
Jurors deliberated for 6 hours before convicting Surratt.
Surratt is still waiting to stand trial on the same charges for the alleged sexual assault of the 16-year-old.
A Roswell, NM judge decided to divide the cases.