A police officer who detained Timothy Joseph Buzbee on Dec. 9, 1980, shortly after a street robbery, testified yesterday that another officer standing with the robbery victim shook his head negatively or gave him (the police officer) a "thumbs-down" signal after the victim studied Buzbee to see if he was her attacker.

The victim, Dorothy Ann Barr, during testimony earlier this week in Montgomery County Circuit Court, identified Buzbee as the man who grabbed her from behind and wrested a paper bag from her hand on a dark residential street. She testified that when she saw Buzbee later that night she told police she believed Buzbee was her assailant, although he was not dressed in the army fatigue jacket and heavy gloves her assailant was wearing.

Yesterday, Buzbee's attorneys began their defense of the 26-year-old land surveyor, who in addition to the robbery charge is scheduled to stand trial in the coming months on charges of raping five women in what have become known as the Aspen Hill rapes. Buzbee has pleaded not guilty to all of the crimes. The investigaton of the 1980 robbery was renewed last fall after police identified Buzbee as a suspect in the rape cases.

The defense called county police officer Francis Dwyer yesterday as its first witness, in an attempt to show that police failed to arrest Buzbee the night of the robbery because they did not think they had "probable cause" to charge him. Officer Phillip Metz, who talked with Barr as she studied Buzbee that night, was killed on duty in March 1981. Under questioning by attorney John C. Monahan, Dwyer testified that Metz gave him a "negative signal" after Barr had stood looking at Buzbee.

The defense also called Buzbee's father, William M. Buzbee, to the stand. He testified that his son often worked late hours doing field work in residential neighborhoods for the surveying business the elder Buzbee owned.

One witness has testified that Timothy Buzbee, who was wearing a short-sleeved shirt and no jacket when he was stopped that December night in the Four Corners area, told him he was in the neighborhood jogging.