A 26-year-old Northwest Washington man was found guilty yesterday of several charges of armed robbery, assault, burglary and possession of illegal narcotics.

A D.C. Superior Court jury took one hour to assimilate four days of testimony and find John A. Austin of 1420 Chapin St. NW. guilty of four counts of armed robbery, three counts of assault with intent to rob while armed, possession of marijuana, and first degree burglary.

Assistant U.S. Attorney James F. Hibey argued that Austin was one of five persons who executed an armed robbery Aug. 5, 1977, a house at 611 Martin Pl. NE, where a high stakes card game was in progress.

Austin and his four codefendants, who have all pleaded guilty in the case, were stopped by police and arrested shortly after the robbery.

Attorney Lucinda Riley, who represented Austin, argued that her client was insane at the time of the incident. But a psychiatrist called by the defense agreed with the prosecutor that Austin was "criminally responsible" for his acts.

Austin, who has been charged with seven other felonies in the District, including two murders, is also awaiting trial in Fairfax County in connection with the August 1977 throat-slashing of two men and two women.

Judge Sylvia Bacon scheduled Austin's sentencing for March 17. He is being held without bond.