A woman who dated James Holmes before the Aurora movie theater shooting began to testify Wednesday afternoon.
The prosecution called his ex-girlfriend, Gargi Datta.
Datta was in the Biological Basis of Psychiatric and Neurological Disorders class with the gunman in the spring of 2012, according to a document listing student presentations. She was studying paranoid disorders.
In a videotaped interview with Dr. William Reid, the gunman said they dated for about six months, and he told her some of his disturbing thoughts.
When she took the stand Wednesday, Datta explained that her first date with the gunman was during a horror film festival. It was a casual, yet physical relationship, she said.
However, she began to separate herself from him in early 2012 and they broke up in February of that year.
"I was getting distant from him," Datta testified Wednesday.
"Why?" asked District Attorney George Brauchler.
"I had already told him from the start that it would be a casual relationship and I did not really feel much closer with him, so I wanted to break up with him," she replied.
"Do you have a sense of how he felt towards you?" the DA asked.
"I think he liked me more than I liked him," the ex-girlfriend said.
She also testified about his demeanor at school and how he interacted with her alone.
"He never had highs and lows of emotion... He was pretty calm for the most part; friendly if people interacted with him," Datta said.
When prosecutors asked her to describe the gunman's apartment during that time, she said his living room and kitchen were extremely clean, but his bedroom was often messy with clothes strewn everywhere.
Thursday, Datta is expected to testify about emails, texts and voicemail messages she exchanged with the gunman.
She was one of the last people to leave a voicemail for the gunman, according to records. It was left on July 20, 2012 - after the mass shooting.
In at least one message, sources say, the gunman tells Datta he wants to kill people. Datta reportedly asked if he wanted to kill her and he replied that would be "too personal."
The interview with Dr. Reid also revealed that the gunman sent Datta a text that read, "Killing is considered evil by society."
Datta encouraged him to get help and recommended a social worker, Margaret Roth.
Roth described him as "the most anxious person I have ever seen," attorneys said during their opening statements. She saw him once before referring him to psychiatrist Lynne Fenton.
Prosecuting attorneys will argue that all of this is important evidence in their quest to prove the gunman was legally sane at the time of the mass shooting.
The gunman has pleaded not guilty by reason of insanity. His defense claims he has a mental illness and was suffering from a psychotic delusion the night of the mass shooting.
Two state-appointed psychiatrists have testified that they believe the gunman is mentally ill, but that he knew right from wrong when he opened fire in the theater on July 20, 2012.
Twelve people died and another 70 people were hurt.