Canadian actress Genevieve Sabourin, who is accused of stalking actor Alec Baldwin, was sentenced to one month in prison for several outbursts during proceedings. This means she could remain in jail throughout the rest of the trial, the BBC reports.
Sabourin, 41, was found in contempt of court a day after she repeatedly interrupted as Baldwin tearfully gave evidence against her.
She is accused of leaving up to 30 voicemails a night and turning up at his homes and a public appearance.
Baldwin denies having a relationship with Ms Sabourin, whom he met in 2000.
Ms Sabourin, who was arrested in April 2012, is charged with 24 counts of harassment and stalking and could face up to a year in prison if convicted.
Ms Sabourin, who also sent Baldwin, 55, a string of emails, has insisted that she and the actor had a romance.
The 30 Rock star, who says he only met her at the request of a mutual friend to offer career advice, told the court on Tuesday how both he and his wife felt "extremely threatened". His testimony lasted only two hours.
The judge had warned the actress, from Montreal, that he might remove her from court after she interrupted proceedings with repeated outbursts.
"He's lying," she shouted at one point. Later, when Baldwin denied having been romantically involved with her, she exclaimed: "You have a scar!"
Eventually, Judge Robert Mandelbaum scolded: "Don't testify from your seat at the defence table while the witness is on the stand."
"Your honour, he's lying," Ms Sabourin replied.
As she was found in contempt, Ms Sabourin said the strain of the trial had made her "a person who is totally exhausted, humiliated, beat up, destroyed, alone".