One of three men implicated in the May 23 incident in which outsiders broke into the Lorton prison and killed an inmate was sentenced yesterday to 10 years in prison.

The sentencing of John Elbert Landon, who pleaded guilty to assault and attempted murder charges in what sources described as an exchange for his testimony, came before a federal judge in Alexandria rejected requests to move the trial of the other two suspects to another city.

Judge Albert V. Bryan Jr. rejected the claim that publicity had precluded the possibility of a fair trial here for Edward Ford Sharrieff, 32, and Germain F. Stoddard, 34.

The claim was one of several pretrial defense motions heard yesterday by Bryan in U.S. District Court. The judge also rejected requests by the defense to try the two men separately.

Sharrieff and Stoddard are charged with the fatal shooting at point blank range of convicted drug dealer Douglas M. Boney. The incident occurred in a minimum security dormitory at Lorton, the District of Columbia's prison in Virginia.

More serious charges than those on which Landon was sentenced yesterday were dropped in June only a day after a federal jury indicted all three men.

Federal prosecutors have refused to confirm or deny that a deal was made with Landon.