Jodi Arias Murder Trial: Victim's Ex Testifies

latest dramatic testimony in the breakup murder trial. Just when you think things could not look worse for jodi arias and her defense team, they make another move that backfires. This time, calling... See More

latest dramatic testimony in the breakup murder trial. Just when you think things could not look worse for jodi arias and her defense team, they make another move that backfires. This time, calling the victim's ex-girlfriend to the stand. Ryan owens has the details. Reporter: Jodi arias' is doing their best to put the victim, travis alexander, on trial. They called an ex-girlfriend of the 30-year-old businessman to show he was a liar and a cheater. He was cheating on me. Do you know who he was cheating with? Yes. Who is that? Jodi arias. Reporter: Pretending to be something he wasn't. After travis' death, were you shocked to learn that he was not a virgin? Yes. Reporter: Arias admits she repeatedly stabbed and shot alexander, but claims it was self-defense her attorneys are trying to convince the jury, he was a sexual deviant that abused her. When daidone was ask if she had seen a violent side? No. Did you feel pressured to do anything? No. Reporter: And her answer to another question, may have dealt a real blow to the defense. Did you ever refer to jodi arias has a stalker of travis alexander? Yes. Reporter: There were fireworks wednesday, when the prosecutor showed a graphic autopsy photo. You think in your mind, because you were the one that was experiencing, did you think -- objection. That is completely irrelevant. It shocked the witness. Travis' sisters gasped. Even jodi arias was crying. But the prosecutor kept going. Do you think it is appropriate to take a knife and slash somebody's throat. Relevance. Reporter: The theatrics frustrated arias' attorneys. But the damage was done, on a day that was supposed to belong to the defense. For "good morning america," ryan owens, abc news, phoenix.