(CNN) Former Dallas police officer Amber Guyger insisted on the witness stand that her shooting of an unarmed black man in his apartment was "not about hate" but about her fear that he would attack her.

Guyger, who was convicted of murder this week in the shooting death of Botham Jean , maintained that she feared for her life, believing he was an intruder in what she thought was her apartment.

But in the sentencing phase of a case that has become part of the national conversation on policing and violence against people of color, prosecutors introduced text messages in which Guyger made offensive statements about the Rev. Martin Luther King Jr. and black colleagues on the police force.

Defense lawyers objected to introducing the statements to the jury that could sentence Guyger to life in prison, arguing that the messages weren't relevant to the conviction and could be prejudicial.

The Martin Luther King Jr. Day Parade

In one chain of text messages between Guyger and others, they lamented having to work the Martin Luther King Jr. Day Parade in January 2015.

A person in the chain asked of the parade, "When does this end lol."

Guyger replied, "When MLK is dead...oh wait..."

In a March 9, 2018, exchange of text messages with a married officer and her former police partner, Martin Rivera, with whom Guyger was having a sexual relationship, she mocked black officers.

"Damn I was at this area with 5 different black officers !!! Not racists but damn," Rivera wrote.

"Not racist but just have a different way of working and it shows," Guyger replied.

Guyger, who is white, testified that after working long hours on September 6, 2018, she returned to her Dallas apartment complex. In uniform but off duty, she approached what she thought was her apartment. She noticed the door was partially open, saw a man inside whom she believed to be an intruder and fired her service weapon, killing him.

But she was actually at the apartment directly above hers — which belonged to the 26-year-old Jean, who was black. Prosecutors said Jean had been on the couch in his shorts, watching TV and eating vanilla ice cream when Guyger walked in.

Another text message exchange introduced at her sentencing occurred just two days before Guyger fatally shot Jean.

On September 4, 2018, a person named Ethridge appeared to playfully offer to give Guyger a German shepherd.

"Although she may be racist," Ethridge wrote.

"I wish I could have one," Guyger responded. "But not in this apartment :( smaller than my old one." She added seconds later, "It's okay, I'm the same."

Rivera testified he deleted the texts between him and Guyger from the night of the shooting,

"That's not something that I would want to be reminded of," Rivera said. "And I don't keep messages saved unless it's of an importance to me."

After the verdict, S. Lee Merritt, an attorney for Jean's family, called the murder conviction a "huge victory," not only for the victim's family, but also "for black people in America." Few police officers ever face trial for shooting deaths, and even fewer are convicted.