Defendant was found guilty by a district court jury of assault in the first degree, Minn.Stat. §§ 609.05, 609.11, and 609.221 (1980), for participating in the brutal beating of a fellow inmate in an incident on September 20, 1980, at Stillwater prison, where defendant is serving a life term for first-degree murder. The trial court sentenced defendant to 76 months in prison, which is the presumptive sentence established by the Sentencing Guidelines for assault in the first degree (severity level VIII) by one with defendant’s criminal history score (three). The trial court also ordered that the sentence run consecutively to the previously imposed sentence for the murder. The sole issue on this appeal from judgment of conviction is the sufficiency of the evidence. The victim, who suffered serious head injuries, had no memory of the incident. The state’s key witness was a fellow inmate who knew defendant well. He testified that he observed defendant administer a number of blows to the victim’s head with a steel pipe about 2 feet long. Defendant denied this, and a friend of his corroborated his testimony. We are satisfied that the jury was justified in crediting the testimony of the state’s eyewitness and in discrediting the testimony of defendant and his friend.

Affirmed.