Prosecutors in the case allege that Arias was jealous that Alexander was dating other women and killed him at his home in Mesa, Ariz. In earlier testimony, they presented photos showing blood-splattered walls and floors in the bathroom and bedroom of Alexander's home, and photos of Alexander's wounds.
Burns, who knew of Alexander but did not know him well, said that he had no idea Arias was still seeing Alexander when the two began talking frequently on the phone and online and planning visits to see each other.
The prosecution presented parts of their online conversations, in which Arias tells Burns about being "cheated on twice" before and having "trust issues" with Alexander.
She also told Burns that she had converted to Mormonism because of Alexander.