Their first date was a horror film festival and they grew closer after that, sharing nights together at home watching movies or playing board games with friends.

But a former girlfriend of Colorado theater shooter James Holmes didn't want anything more than a casual relationship, she testified in his death penalty trial. She broke it off.

' I think he liked me more than I liked him'

- Gargi Datta

"I told him that I didn't see a future with him," Gargi Datta said Wednesday in her first public comments since the July 2012 shooting at a suburban Denver movie theater that left 12 dead and 70 injured.

Datta will continue testifying Thursday about the messages and emails Holmes sent her in the months that they dated. Prosecutors have said Holmes sent her messages saying he wanted to kill people, but she didn't take him seriously and suggested he see a therapist.

Their breakup in February 2012 was a catalyst to the shooting five months later, District Attorney George Brauchler said. He said she was Holmes' first romantic relationship.

In brief questioning before court adjourned Wednesday, Datta said she met Holmes in 2011 at the graduate school they attended outside Denver. She described him as a bright but shy neuroscience graduate student at the time.

"He wouldn't go up and interact with people," Datta said, adding that Holmes was more talkative when he was alone with her.

They started spending time together after she invited him to a study session. Holmes emailed his phone number to her and said that if she texted him,

"I will tell you an amazingly, best-ever world's greatest knock-knock joke."

Datta said they were spending one or two nights a week together in the months before the shooting. After they broke up, Holmes never revealed to her that he was amassing an arsenal of weapons and body armor in meticulous preparation for the attack, prosecutors said.

Holmes has pleaded not guilty by reason of insanity in the shooting. Prosecutors contend Holmes was sane and are seeking the death penalty.

In court, Datta never looked directly at Holmes and repeatedly referred to him as "the defendant" rather than his name. Holmes swayed in his chair as she spoke but had no other visible reaction.

In a video played earlier in the trial, Holmes said he fell in love with Datta. He had written about her in emails to his parents, saying he had cooked dinner for her on Valentine's Day. The two played board games together with friends, watched movies at home, shared dinners and were in the same stressful classes, Datta said.

But Datta said she wanted to end the relationship in January 2012 when she returned from winter break.

"I had already told him in the start that it was a casual relationship," she testified. "I didn't feel I was getting closer to him. I think he liked me more than I liked him."