Leon Mitchell Owensby was convicted in D.C. Superior Court yesterday of kidnapping, rape, sodomy, assault and robbery in connections with separate attacks on three women and a 10-year-old girl in Northwest Washington.

The jury of four men and eight women deliberated only 20 minutes at the close of the three-day trial before returning its verdicts. Judge Nicholas Nunzio set sentencing for March 4.

"In 6 1/2 years on the bench I have never commented on a jury verdict, but I suggest that you have returned justice in the District of Columbia tonight," Nunzio told the jurors as he dismissed them.

Owensby, 23, an unemployed restaurant worker who gave an address in the 1800 block of Maryland Avenue NE, faces a maximum sentence of life in prison.

All the attacks occured on McMillan Drive NW, a quiet, deadend street near the Howard University campus that overlooks McMillan Reservior. They took place between October, 1975, and April 26, 1976, when Owensby was arrested in the company of his fourth and final victim.

All four victims testified at the trial. One of them said she escaped before she had been sexually assaulted. Two said said Owensby had threatened them with a knife. One said he had used a pistol.

The fourth said Owensby had offered to give her a ride to her home, had driven her instead to the McMillan Drive location, raped her, and robbed her of $3.

Owensby, who remained impassive throughout the trial, took the witness stand on his own behalf. He contended that he had been in Marion, Ind., when the first three attacks occurred.

In regard of the fourth, he said there had been no attack and that he had not engaged in any sexual act with the woman.