Sherry Windt, the 18-year-old Bethesda girl charged with stabbing her mother to death, yesterday was judged to be legally sane at the time of the killing, and this morning - more than two years after the crime - Windt is scheduled to stand trial for murder.

However, yesterday's ruling still leaves Windt in the jurisdiction of the Montgomery County Juvenile Court. Under the rules of that court, she will be released from custody by the time she is 21, regardless of the trial's outcome.

The trial is expected to be short. The prosecution will present a single statement of facts, rather than a group of witneses. It is not known whether the teen-ager will present a defense but her attorney, Lester Madder, said she will not plead guilty.

The reason for this truncated trial is that "the outcome that the state and the defense want is pretty much the same - treatment for Sherry," according to Assistant State's Attorney Ann Harrington.

The ruling yesterday by Montgomery County Juvenile Court Judge Douglas H. Moore Jr. ends more than a year of legal maneuvering by Windt's attorney, who has maintained that she was in a trance-like "dissociative state," cut off from reality when the crime occured. Yesterday, Windt, thin and looking older than her years in a smart tailored dress, sat impassively staring at her hands as Moore rendered his decision.

Originally, Windt was charged with first degree murder as an adult in Montgomery County Circuit Court. But Madden last June won the transfer to juvenile court after psychiatrists testified that trying Windt as an adult on criminal charges "would be detrimental to her treatment program."

As he began yesterday's proceedings before a handful of spectators in his tiny courtroom, Moore stated that his decision on the sanity question is "somewhat academic. Regardless of the outcome of the decision the end result is easy to speculate on. She is in need of treatment."

Windt is currently receiving treatment at a Baltimore-based Institute of Psychiatry and Human Behavior, and will remain there as the proceedings continue.

Windt's mother 42-year-old Marjorie Windt, an advertising executive, was stabbed to death Oct. 15, 1975, in the bedroom of the posh Bethesda apartment she shared with her daughter.

Sherry Windt, then a student at the Holton Arms School, allegedly summoned a family friend to the apartment telling him her mother had committed suicide. A few hours later, police charged her with the murder.

Since then Windt has undergoned almost two years of psychiatric evaluation. During weeks of hearings over two years two sets of psychiatrists have taken the witness stand and given conflicting opinions on whether Windt was legally insane when the crime occured.

All have agreed that Windt was a deeply troubled young woman .

Psychiatrists called by the defense have testified that she was a dependent little girl forced to be an adult too early in life - a child who Marjorie Windt grew to regard as an adult confidant.

Bottled-up feelings of hostility and loneliness erupted and forced her to retreat into "dissociative states," according to Dr. Reginald S. Lourie,a psychiatric consultant to the National Institues of Health.

Lourie testified tha tWindt was in such a state, cut off from the real world, on the night Marjorie Windt was stabbed. Windt also told her doctors that she rememners nothing of that night or of the two weeks preceding it.

However, psychiatrists called by the prosecution said they doubted the "dissociative state" theory.

A Bethesda psychiatrist who treated Windt late in 1974 testified she was suffering from some mental disorder but not from "dissociative reactions."

A Massachusetts-based group of psychiatrists sent a report to the judge who originally handled the Windt case, casting doubt on her alleged amnesia. The report said Windt's description of amnesia sounded "like a fantasy of what an amnesia might be thought to be."

Moore noted yesterday he believed that Windt was suffering from a mental disorder when her mother was killed, But he said that the description of "trance-like state" did not allow him to find her insane under Maryland's definition of insanity.