ST. LOUIS (AP) – A judge on Monday will consider whether the pivotal witness in Missouri Gov. Eric Greitens’ criminal trial – a woman involved in an affair with him – should be prohibited from testifying.

Circuit Judge Rex Burlison will preside over the hearing, just a week before Greitens stands trial for felony invasion of privacy.

The married Republican governor is accused of taking an unauthorized photo of the woman during a sexual encounter in 2015, before he was elected. Later this week, lawmakers convene in special session to consider impeachment.

Defense attorneys contend the woman’s testimony has been tainted by the misdeeds of William Tisaby, a private investigator who interviewed her. They’ve accused Tisaby of lies and withholding evidence.

Her testimony is crucial since prosecutors haven’t obtained the photo Greitens allegedly took.