DALLAS (CBSDFW.COM) – Before testimony even began, drama appeared to be unfolding in the murder trial of former Dallas officer Amber Guyger.

The trial over whether Guyger committed murder when she shot and killed Botham Jean in his apartment began Monday morning. She claims she thought she was in her apartment and that Jean was an intruder.

During the beginning of the trial, there appeared to a tense moment when someone’s laptop began playing music out loud inside the courtroom. Judge Tammy Kemp ordered the device to be removed and gave a firm warning that electronic devices were not allowed inside.

Later in the morning, prosecutors and defense attorneys sparred over whether messages between Guyger and her patrol partner should be admissible, including a phone call between the two just three minutes before Jean was shot.

Prosecutors said the text messages and calls contradict Guyger’s claims that she was tired from working a 12-hour shift. They claim she was making plans to meet with her patrol partner after she got home.

Guyger’s attorneys believe the texts are irrelevant to the facts of the case and would make her look bad in the eyes of the jury.

A mistrial was also considered later in the morning after Kemp found out what Dallas County District Attorney John Creuzot did a TV interview with a local media outlet that aired Sunday night.

The defense attorneys argued that the interview was a violation of the strict gag order the judge placed on all parties.

However, Kemp soon overruled the request for a mistrial due to the interview. The trial appears to be continuing as normal.

CONTINUING COVERAGE: The Amber Guyger Trial