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Watching on her TV as Senator Kamala Harris campaigns for the Democratic presidential nomination, Renata Espinoza stares and shakes her head. "It upsets me because I see her doing that now…" she tells CNN.

In 2004 Renata Espinoza became a widow after San Francisco police officer Isaac Espinoza was murdered on duty. And even before she spoke to the family of the slain officer, Harris, the then newly elected San Francisco County District Attorney, held a press conference to say she would no pursue the death penalty in the case.

The Espinozas still do not understand why Harris did not seek the maximum punishment possible for Isaac's death. In 1973, California passed a "special circumstances" law, making the murderer of a police officer eligible for the death penalty.

"I felt like she had just taken something from us," said Renata Espinoza. "She had just taken justice from us. From Isaac. She was only thinking of herself. I couldn't understand why. I was in disbelief that she had gone on and already made her decision to not seek the death penalty for my husband…I want people to know everything about her, even in the past, before they vote for her. And I want them to hear Isaac's story."

On the presidential campaign trail this month, Harris called Officer Espinoza's case "an absolute tragedy," and said her office "prosecuted that case with all the resources that we had."

Asked whether she regrets not speaking to the family before announcing the death penalty would not be sought, Harris said, "I did not ask for permission to make my decision."

Espinoza's killer David Hill is now 36. He's an inmate at the maximum-security California State Prison.