The capital murder trial began Monday for the man accused of killing a Dallas pediatric dentist three years ago.
Authorities allege that in September 2015, 33-year-old Kristopher Love was hired as the triggerman in a murder-for-hire plot against pediatric dentist Kendra Hatcher.
Detectives say Brenda Delgado became obsessed with her ex-boyfriend's new relationship.
Hatcher was found shot in the head in the parking garage of her Uptown apartment.
Love could face the death penalty if he is found guilty. Delgado was captured in Mexico but will not face capital punishment as part of an extradition agreement.
Much of the trial concentrated on Delgado, rather than Love, as she is a central figure in the case.
She will face her own trial at a later date.
Lead prosecutor Kevin Brooks told the jury in his opening statement 'after [Paniagua] broke it off with Brenda [Delgado], she could not let go. You'll see evidence that Brenda started following him."
Paniagua testified that he ended the on-and-off again two-and-a-half-year relationship with Delgado in February of 2015 but remained "platonic friends" with her and would sometimes run into her.
"I would go running at the Katy Trail and sometimes when I was running she would be running the opposite direction," said Paniagua.
Prosecutors contend Delgado began to follow Paniagua and any woman he dated — first one woman, and then Hatcher.
"And Brenda is able to tell that this thing is moving fast, and Brenda is extremely upset," said Brooks. "And Brenda very quickly comes to the decision that she wants Kendra Hatcher killed."
Paniagua was asked if he ever told Delgado about Hatcher, he responded he only told Delgado he was in a relationship and it was going well.
Two people, including a family member of Delgado, took the stand for the state on Monday saying Delgado approached them offering money and a new car if they would attack Hatcher, and possibly Paniaugua as well.
"She said she wanted me to hit [Hatcher] with a bat," said Moses Martinez. "And that's when I told her I didn't want to do that, hurt somebody innocent."
Jennifer Escobar also took the stand and told a similar story.
"To follow around Hatcher and basically eliminate her. [Delgado] had so many ways," Escobar said.
Love is accused of accepting the murder-for-hire plot in exchange for money and drugs.
He is accused of gunning down Hatcher as she returned home and then leaving with an accomplice in a getaway vehicle.
Dallas County has not sent anyone to death row since 2013.
The trial will continue Tuesday morning.