A judge in the US state of Kentucky has ruled that the wife of a murder defendant must testify against her civil partner, despite state law exempting spouses from being compelled to testify against each other, because of a lack of legal recognition of same-sex marriages in the state.

Judge Susan Schultz Gibson, at Jefferson Circuit Court, ruled on Monday that it is “abundantly clear”, that same-sex marriages are not recognised under Kentucky law, despite that “the legal, social and moral landscape against which this issue is playing out is rapidly changing and progressing.”

Prosecutors have argued that Geneva Case had heard her spouse Bobbie Jo Clary, admit to killing a man two years ago, and that she saw her clean blood out of the man’s van, and abandon it in Southern Indiana.

For this reason they have argued that Case must testify on those facts, despite that the couple entered into a civil union in Vermont in 2004, because Kentucky does not recognise civil unions or marriages.

Case had told prosecutors that she would not testify, and invoked the Husband Wife Priveleged, under state law, where a spouse can refuse to testify as to events occurring after their marriage.

Gibson noted that in 2004, the Kentucky General Assembly, “perhaps anticipating that public opinion would one day shift in Kentucky as it has in other states,” put the issue of same-sex marriage to voters, which resulted in a constitutional amendment to specify that “only a marriage between one man and one woman shall be valid or recognized as a marriage.”

She went on to say that it was not up to her to decide “whether these Kentucky laws are constitutionally repugnant,” although she did note that “the acceptance of same-sex marriage is growing and that an increasing number of citizens of this country and this state believe that extension of basic rights taken for granted by heterosexual couples to same-sex couples will not result in the destruction of civilization, but in the enrichment of it.”

The judge went on to say that she was not compelled to decide the constitutionality of the issue because the couple were not considered married in either Vermont or Kentucky. She noted that the couple had not applied for a marriage licence in Vermont, despite equal marriage becoming legal in 2009.

Attorneys for the couple, have argued that they are legally married, and that denying the the same marital rights as others is a violation of the state constitution. Case and Clary claim they are being discriminated against because of their gender, and their sexual orientation.

This case represents the first legal test of the state forcing same-sex partners to testify against each other in such circumstances.

Clary was charged on 29 October 2011 with murder and robbery of George Murphy, and accused of fatally wounding Murphy with a blunt object in his Portland Home. Clary claims self defence, saying that Murphy was raping her, and that she fought back by hitting him in the head with a hammer.

The trial is scheduled for February. Clary is charged with murder, robbery and tampering with physical evidence.

Bryan Gatewood, representing Case, said he was disappointed with the judge’s ruling, and that he would discuss with her whether to appeal. He said that the couple were “for all intents and purposes” married, and would expect to be treated so.