The Arizona Republic, David Wallace, Pool, Associated Press
Jodi Arias, right, sits next to her attorney Jennifer Willmott during the sentencing phase of her retrial at Maricopa County Superior Court in Phoenix on Tuesday, Oct. 28, 2014. Arias was found guilty of first degree murder in the death of former boyfriend, Travis Alexander, but the jury hung on the sentencing phase, unable to choose life in prison or the death sentence.

PHOENIX — The judge in the Jodi Arias sentencing retrial has barred the public from watching the first witness called by the convicted murderer in her bid to be spared the death penalty for the brutal 2008 killing of her former boyfriend.

Maricopa County Superior Court Judge Sherry Stephens said Thursday that the witness will not testify unless the hearing was closed to the public.

"This was not an easy decision," said Stephens, who declined to reveal the witness' identity.

The judge said her decision to close the courtroom and seal the witness' testimony until the sentencing trial's conclusion is necessary for "the administration of justice."

The discussion among the attorneys and judge over the issue was conducted in private.

Chris Moeser, an attorney for The Arizona Republic, argued that the First Amendment allows reporters to attend the hearing and unsuccessfully requested that a transcript of the witness' testimony be made available promptly.

Stephens allowed the family of victim Travis Alexander to remain in the courtroom.

Arias was convicted of murder last year in Alexander's death, but jurors deadlocked on whether she should be sentenced to life in prison or death. A new jury has been picked to decide her sentence.

Footage of the first trial drew a global following, but Stephens has barred the broadcast of footage from the sentencing retrial until after a verdict is reached.

Arias' lawyers had argued that daily broadcasts of the trial might lead to defense witnesses backing out for fear of being harassed or threatened.

Prosecutors said Arias attacked Alexander in a jealous rage after he wanted to end their affair and planned a trip to Mexico with another woman. Arias has acknowledged killing Alexander but claimed it was self-defense after he attacked her.

Earlier on Thursday, two of Alexander's siblings tearfully described to the jury the devastating effect that their brother's death has had on them.

Steven Alexander described nightmares, ulcers and constant trauma from losing his older brother, including locking the doors when he showers.

"When I lay down at night, all I can think about is my brother's murder," Steven Alexander said as family members could be heard crying in the gallery.