Stephen Wyatt Gregory, the 27-year-old Vietnam veteran who held eight people hostage in a Silver Spring bank during a six-hour takeover last February, was found guilty at 4 a.m. yesterday of false imprisonment and assault. The jury deliberated 15 1/2 hours.

Gregory had entered the Blair Park branch of the Citizens Bank and Trust Co. of Maryland with two rifles and held eight bank employees hostage while firing 205 rounds of ammunition around the building, which was surrounded by police.

Defense attorney John G. Gill Jr. had argued that Gregory was not responsible for his actions in the bank by reason of insanity. The Montgomery County Circuit Court jury found Gregory responsible.

"It was the question of insanity that made us take so long," jury foreman Barbara Audel explained as the once solemn jurors walked out of the court building smiling and talkative. "There were some jurors who really had a reasonable doubt of his sanity for a long time," she said, explaining the lengthy deliberation.

The jurors reached their conclusion that Gregory was not insane at 3:05 a.m., according to Audel, and spent the remaining 35 minutes deciding on guilt or innocence in each of the 28 counts against Gregory. The jury acquitted Gregory on one count of false imprisonment and seven counts of assault with intent to murder. Nine counts of kidnaping had been dropped by the judge for lack of evidence early in the trial.

For six days the jury heard testimony as to whether or not Gregory was so severely mentally ill that he was not responsible for the takeover of the bank. Defense psychiatrist Gordon S. Livingston testified that Gregory was suffering from a mental disorder and from the trauma of his combat experience as a marine in Vietnam.

Gregory testified that he did think of Vietnam while he was in the bank and that he felt like "a squad leader" over the hostages. He sobbingly related his experience of being in one battle in Vietnam where he saw a friend "just about blown away" by a mortar shell.

Gregory later said in testimony: "I had only one reason for going into the bank. I wanted to die. I thought I was going to be blown away." Gregory testified to having attempted suicide three times in the past seven years, once by trying to slit his wrist. At his attorney's order, Gregory walked slowly past the front of the jury box with his arm outstretched so the jurors could see the scars remaining on his wrist.

Deputy State's Attorney Timothy E. Clarke argued in closing that Gregory's actions were intended to get attention and that his supposed desire to get himself killed was "a lot of nonsense."

"Did we have a man who was crazy," Clarke asked the jury, referring to Gregory. "No, we had a man who was neat, well-dressed, in no hurry, a bit agressive, and demanding."