A circuit court trial will begin here Tuesday in what is thought to be the nation's first modern test of whether laws against rape can be expanded to cover a man's relations with his wife while they are living together.

John Rideout, 21, is charged with raping his wife, Greta, 23, at their home Oct. 10. The Rideouts were living together at the time of the incident, but Mrs. Rideout has since filed for divorce.

The trial, which is expected to last three or four days, is seen by those involved as having national ramifications on efforts by women's rights groups ot expand protection for women.

The Oregon legislature last year repealed a law that said cohabitation was defense against rape. Rideout is the first man to be charged with rape under those circumstances since then.

The principals in the case have refused to discuss details of the allegations, but one of Rideout's attorneys indicated that the defense quite likely will claim that tradition and common law still protect a husband against a rape charge if husband and wife are living together.

The attorney, Philip Kelley, said the defense would argue that removal of the defense against cohanitation leaves the law silent on the issue and does not necessarily mean that the defense cannot be raised.

Nancy Burch, director of the Salem, Ore., Women's Crisis Service Center, which has been involved in counseling Mrs. Rideout, said she hopes the case will emphasize women's right to protection against domestic violence.

"It's evidently the first time that the archaic notion that a woman is her husband's property. . . is being challenged," she said. She said she hopes the attention given the case - she is receiving inquiries from as far away as Australia and Germany - will encourage other women to seek legal protection in domestic violence cases.

District Attorney Gary Gortmaker's view of the case, though, is that "I think we're going to try the victim first, the law second and the defendant third.

"Unfortunately, that's extremely unfair to the victim. The victim in a rape case is at more of a disadvantage than victims in other cases."

He added, "I would expect in all rape cases- and specifically those involving a husband and wife-that we will have a great deal of background of her prior acts, her thoughts, the philosophy of the wife."

Mrs. Rideout, said Gortmaker, "knows she will be subjected to long, lengthy, piercing questions, not only about the incident but everthing she's ever done of a secual nature in the past year. I could not be in more disagreement with a law that allows that to happen but I have no control over the law."

Rideout, a restaurant cook, was indicted Oct. 18 by the Marion County Grand Jury-the 12th rape indictment in the county this year. He is free on $5,000 bail. If convicted, he faces a maximum penalty of 20 years in prison and a $2,500 fine.

One defense attorney, Charles Burt, said, "There are enough problems with the marital relationship now without allowing one spouse to charge the other with a 20-year felony."

The Oregon legislature, by an overwhelming vote, passed the repeal of the cohabitation defense as part of a series of proposals by women's rights advocates concerning domestic violence.

Until that time, the fact that couples were living together, either married or unmarried, could be used as a defense against a rape charge. Also allowable as a defense was that a couple was married, even though separate, unless a court had entered a decree of legal separation.

Supporters of the mesaure removing the cohabitation defense argue that laws already protect women against beatings by their husbans and that this was a logical extension of the law. Opponents, however, contended that the measure would interfere with marital privacy.

The measure passed the Oregon Senate 2j to 4 and the House 40 to 16, receiving little public attention at the time.

Attorneys researching the laws around the country say they have found hints of similar cases, but no indication that a case similar to Rideout's has been prosecuted in modern times, although some state statutes are silent on whether the cohabitation defense can be raised.