A murder trial in Louisville, Ky., has prompted a legal debate over whether same-sex partners can qualify for spousal-privilege protection and can refuse to testify in court.

Bobbie Jo Clary is accused of beating a 64-year-old man with a hammer, stealing his van, and tampering with evidence to cover up her crime in 2011. Clary claims she used the hammer to protect herself after the man sexually assaulted her. With her trial set to start at the end of the month, Clary’s partner, Geneva Case, has said she does not want to testify.

Under Kentucky law, like in many states, spouses can refuses to testify against one another. Since Kentucky doesn’t recognize same-sex marriage (the state’s constitution defines marriage as between a man and a woman), Case does not have that privilege. Her attorneys argue that Kentucky’s law is unconstitutional, citing the recent Supreme Court cases on the issue of same-sex marriage.

The couple were joined in a civil union in 2004 in Vermont (which did not legalize same-sex marriage until 2009). A county attorney says Case cannot invoke spousal privileges since she and Clary have a civil union, not a marriage. “They have a civil union, if you look at Vermont’s statutes, they distinguish between civil unions and marriage,” said attorney Stacy Greive.

A Jefferson County judge is expected to rule on whether Case will have to testify before the trial starts on August 30. Clary’s attorneys are confident she will be acquitted regardless of whether Case has to take the stand or not.