A Douglas County judge has sentenced an 18-year-old Lawrence man to serve more than three years in prison after a conviction for his role in a Sept. 6 robbery at a south Lawrence apartment.

District Judge Peggy Kittel on Monday ordered Joshua Self to serve 38 months in prison after he pleaded no contest in February to attempted aggravated robbery and conspiracy to commit aggravated robbery. Kittel said Self would get credit for already serving six months in jail, and he is eligible to get credit for another seven months for good behavior.

Prosecutors said Self was instrumental in planning a robbery at The Exchange apartments, 3100 Ousdahl, because he had visited the apartment the night before and believed the residents had high-grade marijuana that could be stolen. Prosecutors allege the group was armed with a BB gun and that one victim was knocked unconscious from a head wound.

Self’s brother, Christopher Self, 20, has pleaded no contest to aggravated battery and conspiracy to commit aggravated robbery. He is scheduled to be sentenced April 22. He was accused of driving the co-defendants to the scene.

Joshua Self’s defense attorney, Napoleon Crews, said Self was remorseful for his actions. Kittel ordered Joshua Self to help pay $1,900 restitution to the victims.

Another co-defendant, Douglas Bittinger, 19, of Lawrence, has a case still pending.