A 26-year-old Laurel woman was convicted last night of all four of last fall's "grenade lady" bank robberies in Fairfax County and of a fifth attempted robbery; the jury recommended sentences that would total 70 years if a judge decides they should be served consecutively.

The Fairfax Circuit Court jury deliberated three hours before convicting Ollin R. Crawford. More than $10,000 was taken in the four successful robberies, none of which has been recovered. There have been no additional similar robberies since her arrest.

Crawford, who is seven months pregnant and took the stand yesterday for an hour to deny involvement in the robberies, sat quietly as each of the verdicts was read. After the third guilty verdict, Crawford lowered her head to her hand and started to cry quietly.

The jury, which could have recommended life imprisonment for each of the robberies, instead called for 15-year sentences for each and a 10 year sentence -- the maximum -- for the attempted robbery. Judge J. Howe Brown Jr. set sentencing for Feb. 22, when he can reduce but not increase the jury's recommended sentence. He can also specify that the sentences must be served concurrently or consecutively.

"I am disappointed, especially in the amount of [prison] time given," said Crawford's attorney, Barbara L. Kimble, who told the jury yesterday that Crawford was "an innocent woman" and that convicting her would "compound a tragedy." Crawford has been held in lieu of $50,000 bond since her arrest Oct. 24 and she was returned to jail last night.

During almost a day of testimony yesterday, the defense produced a string of witnesses who said Crawford was variously at a "crab feast dinner," a friend's home in the District, her own home, at work or a job interview at times that would have made it impossible for her to have committed the robberies.

Much of that testimony came from Crawford's mother, her mother's boyfriend, her car mechanic and her roommate's boyfriend, and some of it was contradicted by prosecution testimony.

In testimony last week, 11 bank employes or witnesses to the five incidents positively identified Crawford as the robber.

The holdups, in Annandale and Springfield during August, September and October of last year, frustrated police for months and triggered one of the most massive and expensive bank robbery investigations in county history.

The day after the fourth robbery, county police staked out more than 40 banks hoping to catch the robber.

The robberies were unusual because they were committed by a woman and because in each case the woman carried a sock with with a lemon-shaped object in the toe that she told bank employes was a grenade.

In the earliest robberies, the woman was reported to have worn purple sneakers, and in all the robberies she was reported as acting coolly. She never wore a mask.

No grenade was found at Crawford's apartment, and police have not found a hip-length gray cardigan sweater worn by the woman in all five robberies.

Describing last week's identification by the of 11 witnesses, Deputy Commonwealth's Attorney V. Britt Richardson told the jury: "They were resolute in their opinion that this defendant committed these crimes; they were positive."

Referring to the 8 of those 11 who picked Crawford out of a line-up, Richardson said, "They said, 'I knew her as soon as I walked in the door.' How many times do you hear that? They said it time and time again . . . . You just can't chip away at 11 identifying witnesses."