A former Gaithersburg man convicted by a jury in October of sexually assaulting his wife was sentenced yesterday to 18 months in prison.

Montgomery County Circuit Judge DeLawrence Beard yesterday sentenced the 27-year-old former lab technician to seven years in prison, but suspended all but 18 months. The defendant's name is being withheld to protect the identity of his former wife. Beard also placed the man on three years' supervised probation after his release.

The Montgomery County case was one of the first under Maryland's new spousal rape law, which took effect in July 1989. The law removed marriage as a defense when a spouse is charged with sexually assaulting a partner.

The man last year repudiated a plea bargain agreement that carried the same sentence that Beard imposed. A jury on Oct. 17 convicted him of two counts of second-degree sexual offense and one count of battery. The jury acquitted him of the more serious charges, two counts of first-degree sexual offense.

At the trial, the victim testified she was forced to engage in intercourse against her will on Feb. 17, 1989, in the couple's home. In addition, the victim said her husband placed a pillow over her face to muffle her screams and used a sexual device on her.

At yesterday's sentencing, the man apologized for "any harm or hardship" inflicted on his former wife, but noted, "Whatever occurred between my wife and myself was entirely mutually consensual."

Prosecutor Barry Hamilton urged Beard to impose a prison term of seven to 13 years, the range recommended under the state sentencing guidelines, as a deterrent for other potential spousal abusers.

But defense lawyer Mark Kappelhoff asked the court for leniency, saying his client had moved to South Carolina and was trying to reestablish his life and career. Kappelhoff said the man had participated in a drug rehabilitation program and planned to attend college.