The Gossip Girl star and Giersch will take their mudslinging into the courtroom, with both parties ordered to take the stand in Santa Monica court tomorrow.
Rutherford and Giersch, both of whom appeared in court for a brief hearing this afternoon, are fighting for primary custody of 2-year-old Hermes.
Over Giersch's objections, the actress is seeking court permission to relocate her son to the East Coast for the next few months while she reports to work on the New York set of the CW hit.
And just in case the drama wasn't amplified enough, the clock is already ticking on the proceedings: Rutherford is expected to report for Gossip Girl duty this weekend.
Further complicating matters, the 40-year-old actress is also four months pregnant with the estranged couple's second child.
In a brief court hearing this morning, Rutherford's attorney, Lance Spiegel, said that the move would be in keeping with little Hermes' bicoastal lifestyle and that interrupting the routine could prove detrimental as the toddler "has never once spent a night away from his mother."
And it's not only Hermes that would suffer, Spiegel said.
The attorney said that Rutherford "would suffer harm because of contractual obligations" should she not be able to travel, ostensibly with her son, to New York. (Producers told E! News last week that they will make arrangements if she is briefly delayed to deal with the court case.)
Takesh Hallin, an attorney for the 34-year-old Giersch, meanwhile, maintained that his client was the boy's primary caretaker. The lawyer called it senseless for Hermes to "be taken care of by a stranger" in New York, when Giersch was available to care for his son in Los Angeles.
Hallin also countered Rutherford's claim that the boy was comfortable living a bicoastal lifestyle, saying Hermes has previously spent only short periods of time in the Big Apple, as opposed to the the months-long sojourn Rutherford is proposing.
A judge has yet to rule on the matter, pending tomorrow's testimony.
The courtroom showdown will bring to a head weeks of heated battles between the duo. Rutherford filed for divorce on Jan. 3 and almost immediately after sought to prevent her husband, who is not a U.S. citizen, from taking Hermes out of the country, claiming she feared he would disappear with the boy.
Giersch quickly fought back, accusing his estranged wife of having a physical temper which at one point included her hurling a laptop at him. Rutherford countered with the latest legal missive, claiming she twice had to call cops on her amateur boxer husband out of fears for her personal safety.